Burners 101

[Mikey98118]

12 hours ago, Frosty said:

Are tea shops good for meeting the local characters and solving the problems of the world?

No; the tea shops have their own commercial vision for success, and their game-plans are different, from one another; it isn't that they are a good alternative. It's more like "any port in a storm" time. If I think much more about this subject, I'm likely to get depressed. "The times, they are a changing."

[Frosty]

Yeah, same here. I used to kill time at a local "specialty coffee / tea shop while Deb got her hair done. They have comfy chairs and little tables but patrons spread themselves as far apart as possible. It's like they're afraid of meeting or <GASP> talking with strangers. a plain cup of coffee was really expensive they don't have a pot going and brew an "Americano" on request. <sigh> Covid put an end to getting hair done till recently and I have the pickup if I need to go somewhere when Deb has the compact suv.

I need to check out the couple local restaurants with a counter to see when they open. I really miss the coffee counter culture. Drinking coffee and watching TV news is getting old, it's been what 4 years now?

Frosty The Lucky.

[Mikey98118]

 

 

                     Using Air/fuel torch-heads

There are a large variety of air/fuel torches, new or old, that can be re-tasked into equipment burners. Recently, I have been seeing MAP gas hand torches marketed online (AKA dual-fuel torch-heads) that are rated to burn propylene as well as propane); some of them feature a stainless steel flame tube (AKA flame retention nozzle), which makes them fit for use as equipment burners; with the addition of a doubling tube to prevent their flame tubes from being rapidly oxidized away in the super-heated equipment atmosphere.

    Some air/fuel torches now come with a short fuel hose, instead of just being mounted on a 16 oz. canister (none-refillable gas cylinder). Separating the torch from its fuel cylinder allows it to be easily positioned at any angle, while the cylinder, which must remain upright, can do so unhindered; but its main value when mounted on a forge or casting furnace is that the fuel cylinder can then be kept a few feet away from the hot equipment.

    The latest versions of air/fuel torches also feature two needle valves. One valve is part of the cylinder fitting, while the other valve is mounted on the torch head. You may wonder why two valves? The answer may be safety. With a separate valve at the fuel cylinder, the hose and torch can be exhausted of positive pressure after shutdown, while a second valve on the torch can then be closed, preventing ambient air from mingling with fuel gas in the hose.

    Without positive pressure, even a needle valve is unlikely to leak, while pure fuel in the gas hose is no more flammable than pure air is. We might think that simply detaching the assembly from the fuel cylinder will do the same job, but the reason that 1 lb. fuel cylinders are not supposed to be refilled is that, once opened, their valves are no longer reliable; they can leak.

    The whole point of discussing air/fuel torches is that they can be used, with some modification, as a practical substitute for 1/4" burners, which can be built, but would cost more than these torches, to do the same job; that job would be running two-brick and coffee-can forges; at less than $30 they can be a bargain.

 

Note: there are fuel hoses of different lengths available, which have various fittings on their ends; some of them have female fittings on one end to connect with a fuel/air torch and a male fitting, with a needle valve included, on the other end to attach to a fuel canister; these allow you to use the torch-head of your choice to do the same jobs cylinder mount torch-heads.

 

    “Flame tubes” are one of the various names manufacturers hang on the combination mixing tube and tip that their air/fuel torches use as flame retention nozzles. I have seen double, and even triple flame tubes on air/fuel torches; so long as their flame tubes are stainless steel, they should work okay inside miniature forges and casting furnaces, for a short while. But, even when their flame tubes are made from stainless steel, things "are no slam dunk." My torch has a single stainless steel flame tube, which has an internal fin for helping to mix the fuel air mixture; that appears to also be stainless steel, but it might have been made of brass in a cheaper torch; this would have made it undesirable as an equipment burner.

    A double or triple flame tube isn't going to be easy to mount in a burner portal opening. More than one flame tube is going to be hard or even impossible to slip a doubling tube onto. My burner's flame tube wall is only about .030" thick. When mounted in a forge or casting furnace, the superheated portion of stainless steel tubing will rapidly oxidize away. Without a thick walled doubling tube, that torch wouldn't last very long. Also a doubling tube allows us to use thumbscrews in the burner portal’s tube to securely hold the torch in place. What it boils down to is that just because we can get away with a thing (for a while), doesn't necessarily mean we should try to.

 

Note: the self-igniting option on air/fuel torches does not usually work for long; its piezo eclectic crystal is durable, but the spark wire portion of the unit can fail in short order. What happens is that for a split-second during ignition there is some blast force generated on the wire’s end; this gradually moves the wire enough to prevent the spark from jumping the gap between wire and the torch body (which provides its ground). You can push the wire back into position two or three times, and then it breaks off. So why is such a poor idea featured on so many torches? To raise their price tags.

 

 

The STK-9 air/fuel torch: I choose this air/fuel torch, not because it will make the cheapest or hottest burner to build, but because it is a reliable model, and allows the easiest miniature burner to construct. Aside from fitting a thicker doubling tube over its flame tube, all other parts are purchased with the torch. Building miniature burners from scratch are only fun for diehard enthusiasts. Furthermore, once you get down to a 1/4” homemade burner size, reasonably priced propane torches can match their output for little more money that you would spend on building materials to construct the burner from scratch. So, for use as air/fuel hand torches, building such burners are largely a waste of time.

    Until recently, canister-mount air/fuel torches didn’t get mini forges and casting furnaces hot enough to be a practical choice; the problem was that their brass flame tubes had to remain outside the equipment’s burner portal, to keep from being melted; this led to excessive secondary air being inducted into the equipment by the burner’s flame; interfering with proper heating.

    Stainless steel tubes have been appearing on some air/fuel torches in recent years, so that they would able to also burn propylene fuel safely (since the Canadian plant was switched over to it in 2008, all so called MAPP fuel has consisted of propylene).     

    A stainless steel tube also allows, “dual fuel” torches to heat miniature forges and casting furnaces (coffee-can size and smaller) efficiently, through mounting in a burner portal exactly like commercial and homemade propane burners; this also holds true for “two brick” miniature forges.

 

The TurboTorch STK-9 dual fuel torch, has a goose-necked stainless steel tube (AKA swivel stem) that is bent at a seventy degree angle; this flame tube, can be rotated through three-hundred-sixty degrees, and then locked in place; this allows the torch to be aimed upward through a forge’s burner port, while its fuel canister remains upright, or remain upright while the burner’s flame tube is aimed horizontally through the side of a casting furnace. The STK9 torch produces 1,800 Btu on propylene fuel; enough to silver braze 1-3/4” copper pipe (Up to 1” pipe on propane), or run a coffee-can forge or furnace on propane.

 

Note: TurboTorch STK-11 is the next step up in heating ability, but at its price you would be as well off to build a 3/8” burner from scratch.

 

Maintenance: While it has a solid reputation, its regulator tends to lose the ability to completely shut off gas flow, over a two or three year period of frequent use as a hand torch; this is only to be expected, since regulators are designed to control gas flow; not to stop it. Ball valves work best as open/close controls. The torch has a three year warrantee available.

    A few plumbers, who reposition the flame tube frequently, have also noticed a leak develop around the tightening screw for the gas tube. A little gas rated medium strength (removable) Threadlocker can solve that problem; keep it away from the last two threads at the nut’s forward end. When mounted in heating equipment, this part should never develop a leak.

    Propane, is not anywhere near as clean as the triple refined butane fuel used in modern blue flame torches and lighters, but the tiny gas orifice typically used on both propane and butane fuel/air torches are pretty much alike. It should not come as a surprise that you will need to clean out the gas jet when using propane fuel. The stem that the fuel runs from the canister through can be unscrewed, soaked in solvent, and then blown out with a canister of compressed air from an office supply store. This torch also has an easily cleaned gas jet orifice screwed into its flame tube, instead of in a hard to clean fill stem (as is common on cheaper air/fuel torches).

 

The protective sleeve (AKA doubler): The end of the thin wall stainless steel that is used for a flame tube will oxidize away, when the torch is used in a forge or casting furnace. Although its crimped end is designed to retain the flame out in open air, it isn’t necessary when the torch is mounted in an equipment portal at an angle, so that the flame can swirl through the equipment’s interior; in that position the flame will be retained without need for the crimp to aid flame retention.

    Therefore, it is prudent to use cheap digital calipers to find the flame tip’s outside diameter, and buy a stainless steel tube to slide over the flame tip, to strengthen and thicken it; doing this at the beginning will also simplify mounting the burner in the equipment’s steel burner portal, without danger of the clamping screws denting the thin walled flame tube. You can buy stainless steel tube cut to size from Onlinemetals.com and from other online retailers, and have the part shipped for very little added expense.

    The flame tube on my STK-9 torch ended up measuring out at 0.505” diameter near its threaded brass air to fuel mixing chamber, and only 0.499” to 0.500” diameter along most of its length. A 5-1/2” long piece of welded #316 stainless steel tube (0.620” outside diameter, and 0.495” inside diameter) costs $5.70 and shipping, cut to length (part # 4236 at Onlinemetals.com).

    Welded tubing has an internal ridge. Cutting a slit through the ridged area will eliminate it and allow the tube to spring open a few thousandths of an inch along most of its length. Leaving the last inch of the tube uncut, and using a grind stone accessory (spun in a rotary tool) to flatten the remaining internal ridge, and then to enlarge the end of the tube just enough for a snug sliding fit, allows it to pushed over the flame tube, also protecting it from being dented by thightening screws during mounting. The doubler tube is 1/2” longer than the flame tube, protecting its end, and greatly slowing high temperature oxidation damage.

    Use a small angle to ensure scribing a straight line on the outside surface parallel to tube’s internal weld bead.

 

Fuel: Available fuel for air/fuel torches include propane, propylene, LPG (which are commercial mixtures containing propane and butane), and pure butane. Both butane and LPG mixtures are available in refillable cylinders in some areas of the USA and in other countries, but their nonrefillable canisters are not the same design as the non-refillable canisters (AKA throwaway cylinders) of propane and propylene, which mount unto different torch-heads.

 

Always read and understand the manufacturer’s instructions before attempting to use an air/fuel torch.

 

Caution: Non-refillable (AKA throwaway) 16 oz. propane and propylene canisters can be refilled from larger refillable fuel cylinders, through use of special connector fittings, but it is illegal to do so, because the valves on those 16 oz. cannisters tend to leak after refilling. For a few more dollars than the refill fittings cost, you can buy an adapter hose, and run your torch from one of the larger refillable fuel cylinders, saving fuel costs legally; but that cylinder must then stay outdoors.

    NFPA (National Fire Prevention Association) safety guidelines state that LPG (liquified petroleum gas) cylinders larger than one pound (16 oz.) are not to be used or stored within habitations; you can assume that will include garages or other structures people frequent. The cylinders are to be stored and used outdoors, out of direct sunlight, on a concrete surface above ground level, in an erect position, and twenty feet from any ignition source, including electrical outlets. Most municipalities closely follow NFPA recommendations in their safety codes. This means that in case of a fire or explosion, breaking NFPA guidelines will almost certainly void your insurance policy, and leave you wide open to devastating lawsuits: LPG products include methane, propane, butane, propylene, and combinations thereof.

    The STK-9’s flame tubes can be positioned to allow a 16 oz. fuel canister to rest below most of a mini-forge or casting furnace’s body, but it is safer to move the fuel cylinder a few feet away from your heating equipment.

    It is a lot handier to move a hand torch independent of its fuel cylinder, and so short extension hoses are marketed for use with air/fuel torches; these have a female connector for a torch-head at one end, and a male connector for a throwaway fuel canister at their other end. Note that not all these products are built with reliable quality; don’t look for the cheapest products, and take the time to read what other purchasers have to say about them before purchase

    Throwaway cylinders get expensive; especially for propylene fuel, so now much longer extension hoses with canister connectors for the torch end and POL connectors for refillable fuel cylinders at their other end, are available online from Amazon’s propane section, and from other retailers.

[Dueldor]

OK fellow metal movers, curious about ribbon burners and size. Has anyone tried to make a ribbon burner for a paint can forge? I have some materials and a consideration to make one using 1-1/2" square tube about 5" long just as an experiment to see if it's possible. I would love to hear thoughts on this endeavor.

[Another FrankenBurner]

It is absolutely possible.

I haven’t seen one in that size, that I recall. In the NARB thread there was a narrow ribbon on a ½” Frosty T burner.

 Are you planning on lots of tiny ports or a few larger ports?

1 ½” seems a tad large for that small of a forge.

Is there a reason you want a ribbon burner in a forge that small?

I’m not trying to discourage.  I hope you do build it and post pictures.  In that size, it might be a picky thing to get balanced.

[Frosty]

Dueldor: You're asking for rather precise answer to a vague question. What size paint can, 1gl. 5gl. Or?

To decide on the size burner you need you must know the volume of the forge chamber. Everything about making a forge work is a game of volume and shape. The forge and burner are two components in one machine.

One of the guys in our club built a forge powered by a NARB driven by a 1/2" T inducer. As I recall the chamber is about 5" x 7" x 9" but a T that size blows dragon's breath about 4+" out each end.

Make a couple sketches so you can measure and calculate the volume and general shape on your proposed forge, we'll be more than happy to offer advice and answers.

Frosty The Lucky.

[Dueldor]

I was honestly just wondering if it would be plausible, but it will be a 1gal can. 1inch of CFI and 1/4" of satanite. By my calculation that gives me a 4" diameter and it's going to be a passthrough so 7-1/2" long. My thoughts and plans on the burner for now is 1-1/2 sq 5" long with 16, 3/16" holes in two rows of five and one of six. Spread over the face and a 1-1/2" form  with a 3/4" frosty t. This is all just playing around. My solid fuel forge is just way bigger than I need for most of what I plan to make, and this paint can will be much more manageable in my small (10'x20') shop.

[Frosty]

I re-read your question and you did only ask if it was possible. Yes.

With a 3/4" T driving any burner into that small a volume is a non-starter. IF you could get the burner to work it'd be blowing a foot of flame out each end. 

I'm thinking a 3/8" burner might be appropriate. Number of holes would be something I'd have to experiment with to determine. The # that came to mind to start with was 7-8 holes and tinker from there. I made my plenum from steel and screwed 2x2 lumber with holes drilled in it to it to test burner blocks.

The size steel tubing you have doesn't bother me but you'll have to watch the flame velocity at the outlets doesn't drop below the mix's rate of propagation (flame front velocity) Not quite the same thing but close enough to use. 

Frosty The Lucky.

[Mikey98118]

That is way more flame than such a small space can handle. One-gallon containers are equivalent to coffee-can forges; those can use burners as small as 1/4". A 3/8" burner needs to be turn down quite a bit to run well in them. The problem is back-pressure.

However, multi-flame burner nozzles, a couple of which have been shown on this group, can be sized down as far as you like. Consider a pipe reducer with a stainless steel face plate, with small holes drilled in it. There is always a way to play

[Dueldor]

Well I'm glad I said something rather than just moving ahead with the build at 3/4 lol. I am totally down with trying a 1/4 burner. I don't know if this is 100% true, but I want to say I read some where that to calculate the holes for the ribbon burner that the surface area of the flame face outlets and the burner inlet tube should be the same. Using this math reducing the burner inlet to 1/4" I would need 16, 1/16" flame face outlets. I like the testing with a 2x2 so I will have to do this and let you all know what my results are.

1 hour ago, Mikey98118 said:

Consider a pipe reducer with a stainless steel face plate, with small holes drilled in it. There is always a way to play

What did you mean by this?

[Frosty]

35 minutes ago, Dueldor said:

I read some where that to calculate the holes for the ribbon burner that the surface area of the flame face outlets and the burner inlet tube should be the same.

That sure didn't work for me nor anybody else I know. 

If you make wooden test blocks be aware they will only make a decent model of the burner for a few seconds before the wood starts to burn and screws up the flames. You'll only have a few seconds to evaluate the burn, say about 5-6.

Frosty The Lucky.

[Dueldor]

23 minutes ago, Frosty said:

That sure didn't work for me nor anybody else I know.

Would you even consider this a good starting point? I'm glad I know now that info was no good. I was going into it assuming that it might not be true anyways, but now I know for sure so thank you, sir! That's good to know that the test blocks don't give you long to evaluate also, I will make sure I'm ready before lighting. Really appreciate all the input, thank you for sharing your wisdom!

[Hefty]

In the NARB thread in the ribbon burners sub-section of this category, Frosty said that he started with a very rough 2x the cross sectional area of the mix tube for the combined outlet area, as a starting point to allow for friction etc causing back pressure (this is a very rough paraphrase, don't quote me).

A lot of dimensions in burners can be figured out using ratios, but I don't know if anyone's done enough testing to say whether this one would be a ratio that is linear/scalable, because friction is affected by surface area as well as area and they do not scale directly, one is based on the square of the other. Frosty tested multiple blocks to get the right amount of holes for the T burner he used.

Mikey was suggesting another way to make a multi-flame burner/NARB. instead of a cast block with holes, use a pipe reducer (but in this case your mix tube is the reduced size and the reducer is expanding to a larger diameter) with a SS plate somehow mounted in the end and drill your holes in it. The advantage here might be that you could start with intentionally too-small holes and creep up on the right amount and size by drilling them out bigger and bigger until it is tuned the way you want.

Cheers,

Jono.

Edited August 1, 2023 by Hefty
re-wording a confusing sentence

[Dueldor]

I want to say I recall reading frosty mentioning that. Too many jumbles of info jammed in this old bucket of mine lol. Really appreciate y'all's patients with me. I will let you all know my progress.

[Another FrankenBurner]

I love a good math ratio rule as well but this one is so affected by so many other variables that it won’t ever have a rule of thumb.

What thickness is your port block?  How many ports are there?  What shape are they? What shape and volume is your plenum?  What does the transition from mix tube to plenum look like? What static pressure is the plenum running? Etc. These all could change that ratio.  

Frosty did state that he started at 2x the area of the mix tube on the very first post of the NARB thread. It ended up not being enough for his ribbon. He bracketed what his burner needed. An easy way to figure out what your burner is happy with.

[Mikey98118]

14 hours ago, Dueldor said:

I am totally down with trying a 1/4 burner.

With a multi-flame nozzle, I would bump the burner size to 3/8" because it has a larger turn-down range to play with. Also, It is actually easier to get the 3/8" size right than the 1/4" size. This is because the smaller the burner the smaller any deviation from perfect construction that remains in the ballpark.

Furthermore, linear burners are less finicky to tune in these small sizes. Just a couple of things to think about...

[Mikey98118]

Cutting with a rotary tool: If you stop the disc during a plunge cut (with a circular or a chop saw) before the cut is finished, it will usually cause kickback. The opposite is true when surface cutting on sheet metal products, like pipe and tubing, with a rotary tool and cutoff disc. Attempting to remove a moving rotary tool from the kerf will usually cause kickback.

    Those OEMs (like Dremel Tools) who bother with a thorough list of safety tips in their instruction manuals, all advise the operator to run a cutoff disc back and forth on the part surface, gradually deepening a groove at the cut line, until the disc begins to break through that groove, which is then called a “kerf.” Unlike chop sawing, or plunge cutting through thick parts, the operator is supposed to bring the disc to a halt before exiting the kerf; it is different to other cutting processes, because your disc isn’t deeply buried in the part. There is very little material for the disc to “walk up,” creating an opportunity for kickback, as the disc stops. Also, the numerous tiny grit edges don’t have anything like the tendency to grab unto stock that the teeth of circular blades do. Most kickback from resin bonded cutting discs come from the sides of their discs binding against the kerf.   

    So, surface cutting creates a unique situation, where stopping the disc before removing it from a groove or kerf is safer than removing the disc, while it is still in motion. Die grinders are treated the same as rotary tools for surface cutting (my own description of this technique).

    You will notice that friction makes the disc want to move in one direction; take note of it, and make sure that the disc is traveling in the opposite direction, when breaking through the kerf. Otherwise, the disc will tend to bump against the end of the kerf, creating kickback.

    Maximum safe RPMs of cutoff discs vary by manufacturer and thickness; if a marketer doesn’t list the maximum RPM for a cutoff disc, the rule of thumb is not to use larger than 1-1/4” diameter generic disks at 32,000 RPM, or 20,000 RPM for 1-1/2” generic disks. 

    Brand name cutoff discs (ex. Dremel), and discs used in electric die grinders (1/4” and 3/8” arbor holes) are typically much higher quality, and are designed to run at higher RPMs than generic rotary tool discs. A 25,000 RPM rating is typical of 3” die grinder discs, and 30,000 RPM for 2” die grinder discs. But it is wise to bring the rotation up slowly to those speeds in unrated discs. Better to be safe than sorry.

To avoid surface cutting problems:

(1)   When starting a cut, be sure the accessory is already turning; do not start, or restart a cut, with the tool still.

(2)   Gently lower the disc unto the part surface, with the tool held firmly, and lightly run the disc back and forth on the part surface, next to the cut line, to establish a groove. Deepen the groove by continuing to run the disc lightly back and forth, until it starts to break through the material’s far side; when the groove starts breaking through the material’s far side, it is called a kerf; cutting through the kerf is far more likely to create kickback, then deepening the groove. Don’t press the disc against the part. Just let the disc do the work.

(3)   Always delay cutting into the kerf until you have no other choice.

(4)   Start and stop the cut short of the end of the marked line, and finish the cut later, with a small diameter disc, for greater control, as these two areas are the most likely to create kickback.

(5) Allow the disc to come to a complete stop before removing it from a cut, to avoid jamming the disc, and creating kickback.

(6) A common cause of kickback is a disc that is moving even a little out of parallel to the kerf; the problem is multiplied when the disc is deeply inserted into the kerf. It is safer to only try cutting through the material, after the disk begins breaking through the part’s far surface.

(7) The only relief from torsion kickbacks is provided by Dremel’s EZ-lock mandrel and special cutoff discs; this nearly eliminates torsional forces, making an end-run around that problem. Save the last 1” of their diameters for surface cutting in problem areas, like inside corners.

(8) Another cause of kickback is the disc bumping into the end of the lengthening kerf. Try to only move the disc counter to the direction that friction inclines it to “walk” along the part, once you start cutting into the kerf; this will help you to avoid bumping the disc against the end of the kerf; always ease into the cut, to avoid kickbacks. Aside from cutting through the kerf from the right direction, practical relief from bumping kickbacks is provided by smaller diameter cutoff discs.

(9) When you can, try to cut beside of the cut line, and then grind back to it afterward; this allows you to concentrate on two separate tasks, instead of looking after two cutting factors at one time. After you finish all cuts and remove unwanted material, then start grinding back to the scribe or ink lines with a small stone wheel, or diamond disc. Do not use cutoff discs for grinding; it dangerously weakens them.

Note: The cheap variety of imported diamond incrusted rotary discs are too thin to keep the diamonds on their rims from rapidly being lost; they are useless for steel cutting. However, this doesn’t hold true for the diamonds on their two faces, making them a good choice for precision grinding work.

EZ lock mandrel and cutoff disks are one of safest ways for a beginner to surface cut with a rotary tool; they are more expensive than generic cutoff discs, which run in standard mandrels, but considerably easier for a newbie to deal with, when doing the work needed to build a couple of burners. By the time you use up the disks in one their mandrel and disk kits, you should be well enough acquainted with surface cutting to take advantage of the more economic offers for regular discs and mandrels. You will still find yourself reverting to the EZ lock system for tricky cutting jobs. The special discs that come with this system are 1-1/2” diameters. It is wise to save the last 1” of each disc, rather than wearing them down completely. The small used discs are very handy for making interior cuts in small parts.

    Begin by inserting the EZ lock mandrel all the way into the collet nut on the tool’s spindle, and then tighten the nut. To mount a disk, push the plastic part of the head down against its spring, dropping a disk past the mandrel’s bow tie shaped end piece, and then turn it ninety degrees, to lock it in place.

    You can buy the discs and mandrel in kit form online, and from most large hardware stores. The spring and locking mechanism are what makes this system unique. It eliminates the usual locking screw, so that grinding and sanding wheels can be used nearly parallel to part surfaces, without interference from a protruding screw head. The disc is positively locked, because there is no screw to loosen from vibration, allowing the disc to spin on the mandrel. But most important of all, the spring allows your tool to move out of alignment with the kerf, without creating kickbacks, by nearly eliminating torsional forces.

Disc mandrels: You don’t want to employ just any disc mandrel for steel cutting. The standard jeweler’s mandrel, which only has a 1/16” standard machine-screw head, was designed for making very short cuts in silver and gold ring bands; not for making extended cuts in steel. There are special mandrels with 1/16” crews that have oversize screw heads, threading into oversize mandrel faces, and similar mandrels for 1/8” and 1/4” arbor holes; these far outperform the minimal screw head variety; you can find them offered through eBay, Amazon.com, and through most jeweler’s supply houses; input “SEINC 1/8” rotary tool mandrel” to find them quickly. Preamer 1/8” mandrels are excellent for spinning 1-1/4” diameter fiberglass reinforced aluminum oxide cutoff discs, which are handy for cutting on burner parts.

Note: Poorly finished mandrels, provided along with some cutting discs, can cause cutoff discs and grinding wheels to wobble. This is a common problem that is seldom correctly diagnosed. Customers incorrectly blame the discs. What is actually happening is that the mandrel’s face is out of true right angles to the shank’s axial center. Or, or the washers provided with cheap mandrels aren’t perfectly flat. Circular motion on fine sandpaper can flatten washer surfaces, and the mandrel can be spun in your rotary tool, while its forward face is quickly trued up with a diamond coated cutoff disc, or diamond coated flat file.

[Mikey98118]

On 7/31/2023 at 9:55 PM, Hefty said:

The advantage here might be that you could start with intentionally too-small holes and creep up on the right amount and size by drilling them out bigger and bigger until it is tuned the way you want.

Cheers,

Jono.

You are quite right; I didn't even think of that

[tinkertim]

14 hours ago, Mikey98118 said:

You are quite right; I didn't even think of that

This is how I got my IFB NARB tuned.

[Mikey98118]

Drilling and Threading Stainless-steel

The softer stainless alloys (300 series) tend to gum up tool edges, which then rapidly become dull. Three-hundred series stainless-steel also tends to compress during drilling and threading, when using dull tools, compacting its surface; this is a form of work hardening. That compacted surface becomes denser, and begins to act like a bearing surface; dull cutting edges then ride on it (instead of penetrating): causing rapid heating of the cutting tool, which is why only sharp drill bits should be used on stainless-steel.

    Stainless-steel work hardens rapidly if a dull tool is used, if too little feed pressure is applied, or if drilling fluid isn’t employed; tapping oil is perfect for this, and can be purchased in amounts smaller than a pint). But, even cooking oil is better than nothing. It can take mere seconds to overheat a dull drill bit in stainless, and dry drilling will dull cutting edges rapidly, ending up with melting temperatures on a drill bit’s leading edges; this is followed by transference of some of the bit’s high-speed steel material to the part’s surface. Thereafter, no further drilling is possible, although the resulting mess can be reamed out with diamond coated, or tungsten carbide burrs, applied with diligence.

    When breaking through the far side of a hole, the leading edges of a drill bit can bind in the part’s thinning material, as it deforms; small drill bits snap off at this point. To avoid breakage, ease up on feed pressure when you feel the bit breaking through the far side of the material; this is true for any malleable metal--not just #300 series S.S.

    Pure copper can snap small drill bits at any point during drilling, if more than minimal pressure is used; not just when breaking through the far side of the material.

    It is generally a good idea to employ the drill bit recommended for different metals. The drill bit sizes listed in tap and drill bit charts are normally meant for use on soft metals like brass; they produce a 75% thread engagement. Only 50% thread engagement is recommended for steel alloys. However, the relatively few threads produced in most tubing and pipe are under more than moderate stress at times; this makes the additional pressure on your tap, which comes along with an additional 25% thread engagement, a recommended risk, when mounting set screws in burner mixing tubes. But, when threading through thick and/or doubled stainless parts, used in a burner’s flame retention nozzle, the recommended 50% thread engagement is necessary.

    “High-speed steel” drill bits are the cheapest grade of tool steel; if you are careful, you might get as many as four holes in thin stainless tubing before they need resharpening. “Cobalt” bits are made from high-speed steel, with cobalt added, for further hardening and heat resistance. When you can find cobalt bits with 118° points (standard angle for drilling ferrous metals) in the size you need, they are well worth their higher prices, in hardware stores; they are usually only available in fractional sizes. Cobalt drill bits can be purchased through Amazon.com for the same price as mere high-speed steel bits will cost at a hardware store. Look up any drill bit chart to understand the differences between fractional (fractions of an inch), wire sizes (adhering to wire gauge numbers), letter, and metric drill bit sizes; all of them are a few thousandths of an inch different, than the closest size in one of the other classifications. The harder the alloy the more brittle it is; therefore, treat cobalt drill bits more gently than plain high-speed steel bits, and tungsten carbide bits more gently still; use light feed pressure on cobalt and carbide drill bits; do not forget the cutting oil, and they will serve you well.

    135° split point cobalt drill bits also work well for drilling stainless steel; these bits come in a greater variety of sizes than 118-degree chisel point bits: including number and letter drill sizes. Because they are made for drilling hardened and stainless steels, hard bronze alloys, and titanium (all tough jobs), cobalt bits have thicker webs, leaving smaller clearances than standard bits; which means you will have to work diligently at chip removal. One of the advantages of split point bits is that they do not tend to “walk” (move around on the part surface before penetration) like chisel points do. Try to buy American made M42 (8% cobalt) bits; most of the imported cobalt bits are only M35 (5% cobalt). If you look cobalt drill bits up on eBay (the drop shippers paradise), make sure the bits you choose really are cobalt. Amazon may be a safer market for these bits.   

Note: Sets of tungsten carbide (and of tungsten steel) micro drill bits embedded in 1/8” mild steel shanks are available online for low prices. Tungsten steel will hold its temper up to 932 °F, and tungsten carbide is immune to tempering, but is quite brittle. Common high-speed steel bits lose their temper above 400 °F. 

Threading in stainless steel: The greater thread engagement (75%) needed on thin tubing walls, is one of the reasons you only want to use taper (AKA starting) taps; not plug or bottoming taps. The other good reason is that, unless you are going to start the tap in a drill press, (with the part trapped in a drill press vise, after drilling each hole, without moving the part), it is not likely that the tap will be started at true right angles. Starting taps will self-correct to that position if your aim is “in the ball park.” Plug taps will not. The way to tell the difference in taps is amounts of chamfer in taps are: Bottoming taps (1 to 1.5 chamfered threads); Plug taps (3 to 5 threads); and Taper (8 to10 threads). Lazy sales clerks and ignorant drop shippers are likely to offer plug taps in place of taper taps, so count those chamfers before buying.

    Another difference in tap designations are “straight” hand taps, and “spiral” CNC machine taps. Spiral taps have deeper groves for faster clearance of chips, and are therefore weaker than straight taps; take extra care with small spiral taps; there are other types of thread taps, but these are the most likely types to be offered on line.

    Start threading with your tap as close to right angles as possible, and only turn the tap until you can feel resistance suddenly increase (the “quarter- turn and reverse tool to break burr” rule of thumb is not adequate for stainless or high carbon steels); instead, you must back the tap off as soon as you feel a sudden increase in resistance to movement. It does not matter how little progress you make before breaking the burr away from the thread end, and starting another twist; have the patience to follow this advice. You are going to be using small (and therefore easily broken) taps on these burners.

    Be liberal with your tapping oil, and back the tap out completely (in order to clean out collected metal chips) every full turn; dealing with a broken tap is even less fun than removing high speed steel layers left from partially melted drill bits.

    Should you break a tap off in the hole, gently rap back and forth on the protruding point within the tube (with a rod), to loosen the embedded point; then, try to back it out of the hole with pliers. Otherwise, you must drill that piece of high-speed steel out with a diamond coated or tungsten carbide rotary burr.

    Once the partially threaded hole is cleared, try to continue threading it with a new tap; most likely this will work out well enough to accept a screw, but if there isn’t enough thread left to properly engage the screw, you must start over by drilling and tapping for a larger screw.

    There are three kinds of taps: "Bottom," "plug," and "tapered” (AKA “starting”) It should be obvious that stubbornly insisting on a tapered tap (even if you have to special order it), will return big dividends once you start threading in S.S. Learn the difference between starting and plug taps, to defend yourself against ignorant or lazy sales clerks. It is better to pay a premium price and/or special order a taper tap, than to try forcing a plug tap to work in stainless-steel.

    Any malleable metal will form a raised area on both the near and far surfaces of the part, during tapping; #300 series stainless steel more so than other ferrous alloys. The inside face of threaded holes in the burner’s flame retention nozzle and other close-fitting parts must be sanded flat in order to keep proper fit. After sanding, the tap must be run through the threads again to “chase” them (to help clean out debris and get rid of burrs and/or deformed thread ends). Chasing and sanding the inner face of tubes must be repeated back and forth, until all screws turn smoothly, and the part slides smoothly over other tubing.

[Mikey98118]

Linear burner designs

Jet-ejector burners can induce considerably more air than linear burners. However, this is no great advantage, because linear burners are capable of inducing more air than is needed; their strong points are maximal mingling of fuel gas and incoming air; smoother control; and handier construction choices in small burner designs. On the other hand, the larger the burner the larger its air funnel; this looks crude on larger burners.

    Good combustion requires air to mix thoroughly with a burner’s fuel gas. A swirling motion provides the most mixing for the least drag on your burner’s air-gas mixture flow; jet-ejectors and linear burners both provide this, but linear burners have the edge.

    The first matter to keep in mind about funnels and other constrictive shapes, is the greater the ratio between the air opening’s diameter and the mixing tube’s diameter, the stronger the swirl (vortex) created. So, what ratio is desirable? No less than 2.5:1 for a minimum. 3:1 should be the maximum, as beyond this the swirl in your burner’s gas/air mixture can become a problem for the flame retention nozzle to smooth out.

    The funnel shaped air entrance is connected to the burner’s mixing tube, which for this kind of naturally aspirated design should be nine times the mixing tubes inside diameter. Ten times provide a smoother flame for braze work. Eight times produces a shorter flame for small interiors.

    High-speed gas burners require a flame retention nozzle, if run outside of heating equipment, and will benefit from one, when mounted within a forge or casting furnace. Slide-over stepped nozzles are easiest to build, and more effective on high-speed burners, than the various tapered nozzle designs; their diameters are usually determined by pipe sizes or close equivalents in tubing. If your burner’s mixing tube 3/4” then the flame retention nozzle will use a 1” long spacer ring of 1”, sanded down and pushed into a 1-1/4” stainless steel pipe, which is 2” long, with sufficient set screws to keep it trapped in position with the right amount of overhang (beyond the mixing tube’s end) to be correctly tuned.

    The gas assembly must be mounted at the air opening so that the gas tube and orifice are centered and axially aligned with the mixing tube. The end of gas orifice will provide the most air induction if held at the optimal distance from the mixing tube’s opening; this is a little different for every burner. The practical way to accomplish this is to trap the gas pipe in a mounting plate that is cut out of a flat washer for smaller burners, or made from sheet metal on larger burners.

    Use a divider (best) or compass (workable), and a prick punch, to lay out a disc of the same diameter as the outside of the funnel’s flange. whether you want to silver braze, solder, screw, or glue the mounting plate in position over the funnel’s flange.

    Drill a hole in the middle of the disc for your Rivnut (a threaded insert nut that holds the threaded gas pipe) to be pushed into, for silver brazing, soldering of gluing. Mark out three equal spaces for ribs between the air openings, using a divider or compass (or just use the hex flats of a flange nut). Drill small holes between the areas of the ribs and outside the area of the flange nut.

    Remember that there is no significant air flow in this central part of the opening, so do not shortchange yourself on rib width in this area. The ribs would be too narrow if you kept their lines parallel; that is not desirable. You want the three ribs narrower at their outer ends, and becoming wider toward the center of your disc, to balance maximum air flow with sufficient material strength.

 

Gas assemblies for MIG contact tips

5/16”x 3/16” brass (or low carbon steel) tube can be internally threaded for MIG contact tips; their 3/16” inside diameter can be threaded for the most common thread found in MIG contact tips (1/4-27). The exterior will accept various 5/16” dies (fine thread is better than coarse thread for this, but 5-18 Rivnuts are what is available for use with stainless steel mounting plates). Use this heavy wall tubing with 5/16-36 dies to create small gas tubes that are screwed directly into ¼” thick aluminum mounting plates, and then locked in position with an additional nut.

 Hose barb sizes for 5/16” tube:  Barbed hose coupling sizes match the outer diameter of the narrowest portion of the barb; this leaves no room for threads of those same diameter. Therefore, 5/16” barbed couplings can be threaded to match up with 5/16” tube, only through their thickest sections. 3/8” size barbed couplings can be silver brazed, silver soldered, or glued onto 5/16” tube. If the barb is screwed onto the gas tube, the threaded joint must be sealed with thread locker, to prevent gas leaks.

Lamp thread parts: For people who cannot afford “doing things the right way,” or aren’t able to find all the parts and tools, for externally threading 5/16” x 3/16” tubing, the gas tube can be sanded and pushed into lamp thread parts (externally threaded tubing with matching washers and nuts) from your hardware store’s lamp section (usually located in the electronics area). The gas tube can then be trapped in place by silver brazing, soldering, gluing, or even interference fit; it is the lamp thread that must move back and forth for proper tuning, while the trapped gas tube moves with it.

    Lamp thread tubes at your local hardware store have external 1/8-27 IPS, and internal diameters of 0.285” that will accommodate a 1/4” O.D. gas tube (with a 3D printer nozzle for a gas orifice) or a 5/16” tube (for a MIG tip) after some power sanding; you will find these short tubes with external 1/8-27 IPS thread, matching nuts, and flat washers in the lamp section of your local hardware store.    

    A nut snugged up on both faces of the center hole in a mounting plate can keep everything tightly trapped in perpendicular position, if the plate is screwed onto a funnel flange. Lamp part nuts are not a good choice for silver brazing to the bottom side of the plate. However, these assemblies will only be used on large enough burners to be screwed onto a funnel’s flange; allowing you to unscrew the gas assembly, while it is still attached to the mounting plate, to remove and clean the gas orifice, and then return it to the same position, afterward.

    You do not need to perfectly match up the outside diameter of whatever you use for a gas tube with the inside diameter of the threaded lamp tube. Loose fits are just fine so long as you center the gas tube in place, and prevent movement between the lamp part (threaded tube) and the gas tube. Even electrical tape can be used to provide an interference fit between the gas tube and lamp part. Employ fender washers with 3/8” center holes as mounting plates for the burner’s gas assemblies; they can be enlarged a few thousandths of an inch, to enable lamp thread parts, to move freely within them.

    Thread-locker comes in hardening and non-hardening types; both kinds are resistant to vibration, and the hardening type makes a stronger bond than gasket adhesive, but they are not designed with the same flexibility in mind. So, be sure that the metals you bond with hardening type thread-locker are metals with similar coefficiencies of expansion; such as stainless to mild steels, or copper to brass, or aluminum. Not, stainless or mild steel to aluminum, copper, or brass. You want all the parts to expand and contract from temperature changes at close to the same rate. An aluminum mounting plate on a stainless-steel funnel, or vice versa calls for gasket adhesive, or for screws in slightly oversize holes, so that some part movement can be tolerated. 

    Thread-locker for fuel lines, are rated for use with petroleum products, so you will need it to seal parts of your gas line anyway (just remember that the hardening type of thread-locker, which makes such a good glue, also prevents the MIG contact tip from being unscrewed for cleaning, without first heating it up with a lighter).

 Gas assemblies from 1/8” pipe: What is 1/8” IP thread? 1/8” IP or IPS (iron pipe, or iron pipe standard) thread dies can be used to make lamp rod thread (1/8-27) on the outside of schedule #80 1/8” pipe nipples (nominal size; actual outside diameter of 1/8” pipe is .405”). This is parallel thread, and is not to be confused with tapered 1/8-27 thread, which is used for 1/8” NPT (national pipe thread). Lamp thread dies can be used on the cut off ends of 1/8” pipe nipples, with the other end’s tapered thread left in place, to mount your hose fitting or needle valve to. The internal diameter of 1/8” schedule #80 pipe is about 3/16”; a ¼-27 tap can be used to create one of the most common thread sizes used in MIG contact tips into its end. This means that A contact tip can be easily installed on a ½” or larger size linear burner.

    Lamp thread is too large for convenient use in micro-burners. Fortunately, the same mounting scheme can be carried out by externally threading brass tubing; thus, the right heavy wall tube can be employed in ever smaller gas assemblies, installed on ever smaller burners. Brass 6x4mm brass tubing is available through Amazon.com.  

[Mikey98118]

                     Mounting plates for gas assemblies on linear burners

Mounting a gas assembly has two aspects; what is easiest and what works best. There will be no "perfect” method of balancing these factors, because aside from tooling and skill levels, we all have preferences. Mine is for maximum control of the parts being assembled; having found that we get the best results for the least work, if Murphy’s law is never given a chance to muck anything up.

    Gas assemblies are best mounted on linear burners, by suspending them in mounting plates made from fender washers, of up to 2-1/2” diameter; keeping your labor at a minimum, by doing only part of the work needed to fashion a mounting plate from scratch. For larger openings than 2-1/2” you must lay out the plate with dividers, on sheet metal.

    So, why start with sheet metal, or a fender washer to make a mounting plate? Why not braze together separate parts instead? When you begin with a flat surface; all you need is to avoid bending it, to assure that the gas assembly mounted to it will remain perpendicular to the air opening, and therefore axially true the cone shaped air entrance. Fender washers come in various thicknesses, over which you have little control; because they all have 2-1/2” or smaller diameters, that is okay. But the larger mounting plates that you make from sheet metal need a minimum thickness, to ensure that they stay flat while being constructed, and then mounted. 0.079” thickness in stainless-steel plate is strong enough to stay flat when being silver brazed to a funnel, but not so thick that it is difficult to drill the center hole; then cut and grind three air openings.

    Use a divider (best) or compass (workable), and a prick punch, to lay out a disc of the same diameter as the outside of the funnel’s flange. whether you want to silver braze, solder, screw, or glue the mounting plate in position over the air opening’s flange.

    Drill a hole in the middle of the disc for your Rivnut (a threaded insert nut that holds the externally threaded gas pipe) to be pushed into, for silver brazing. Mark out three equal spaces for ribs between the air openings, using a divider or compass (or just use the hex flats of the flange nut). Drill small holes between the areas of the ribs outside the area of the flange nut.

    Remember that there is no significant air flow in this central part of the opening, so do not shortchange yourself on rib width in this area. The ribs would be too narrow if you kept their lines parallel; that is not desirable. You want the three ribs narrower at their outer ends, and becoming wider toward the center of your disc, to balance maximum air flow with sufficient material strength.

 

[Mikey98118]

                                                    Drilling and threading brass gas tubes

Most brass tubes and pipe fittings that you will buy and turn into burner parts are half-hard brass; this can be drilled and threaded more easily than stainless-steel alloys; however, it can be just as tricky to tap threads into, or run a die down, to make threads as #300 series stainless-steel; it tends to gum up tool edges on dies and taps. Half-hard brass alloys are inclined to compress during threading; this is a form of work hardening. Tapping fluid should be employed during threading; it can be purchased in amounts smaller than a pint). But, even cooking oil is much better than nothing.

    Lots of people lack a drill press, or much use for one; they will be tempted to drill and thread by hand. However, a cheap drill press vice is only about ten dollars, and by placing your parts in such a vice before you try hand drilling, you will drill parallel and at right angles far more accurately. Keeping your tube in the vice will also help you to start a die down the brass tube correctly.

    Start threading with your tap as axially true as possible, and only turn the tap until you can feel resistance suddenly increase (the “quarter- turn and reverse tool to break burr” rule of thumb is not adequate for half-hard brass; instead, you must back off the tap off as soon as you feel a sudden increase in resistance to movement. It does not matter how little progress you make before breaking the burr away from the thread end, and starting another twist; have the patience to follow this advice. You are going to be using small (and therefore easily broken) taps in ¼” and in six-millimeter gas tubes. Also back off the tap every full turn forward, and run it back over the thread you just made to clear burrs, and smooth up the new thread; otherwise, after a few extra twists, so much pressure might be needed to do this, that small taps will break off in the hole. Be liberal with your tapping oil. Dealing with a broken tap is no fun. Should you break a tap off in the tube, gently beat back and forth on its protruding point, to loosen it; then, try to back it out of the hole with pliers; if that does not work, cut away that section of tube, and try again with a new tap. You should have no need to use a drill bit in 4mm inside diameter tubing, and even a plug tap will suffice for the purpose, unless your tubing isn’t actually 4mm inside diameter; that is not very likely, but these are imported parts; which means you are likely to be dealing with an ignorant drop shipping seller (meaning they “don’t know and don’t care”).   

    Use the same techniques for threading with dies as with taps. Remember to grind a short bevel on the end of the tube, to help the die to start threading at true right angles; if you start the die threading close enough to perpendicular to the tube, it will finish truing itself up, within a few twists.

6mm x 4mm (millimeter) brass tubing can be used as gas tubes for 3D printer nozzle gas orifices on small burners. Use an M6x1 tap, to create internal thread for the printer nozzle about ¼” deep in the gas tube. If tube exteriors are threaded with an M6x1 die, stop the external thread short of the tube area with the internal thread.

    Tap the internal thread first, and Screw in a 3D printer nozzle, to check that it is axially aligned. These nozzles are quite short, and unlike soft copper MIG contact tips, they cannot be bent into alignment. If the nozzle is not axially aligned, cut off this short section of tube, and thread for a nozzle all over again. You will only be losing about 5/16” of tube with every failed attempt. It is pointless to go through all the work to center and align the gas tube, otherwise.

     The exterior thread allows you to Silver braze an M6x1 rivet nut to a mounting plate, in place of a standard hex nut. These rivet nuts are 3/4” long, with an exterior lip on one end; their threads end 5/16” short of the end of the nut with an external lip; this makes it nearly impossible to accidentally braze filler alloy on its internal thread. The rivet nut’s full length can be used to help ensure proper axial alignment of the gas pipe and orifice, once a flange nut is threaded onto the gas tube. Rivet nuts are also easily press fit into 1/4” aluminum plate, which can be used to make large mounting plates. Use your digital calibers to ascertain the exact outside diameter of the rivet nut, before ordering a drill bit. It is important to avoid drilling an oversized hole.

Note: You will use two different kinds of nut with the gas pipe assembly. The flange nut has a hex head that can be gripped with a small crescent wrench.  Vice grip pliers can hold the tube, while you start running a die down its length (if you don’t have a press vice). The rivet nut has no head, but can be gripped by those pliers; the tools allow you to jamb these two different kinds of nut together on the exterior thread you are creating, once you have threaded a sufficient length of the tube, so that you can more easily finish threading its exterior, if you do not have a drill press vice.

    The gas tube’s exterior and interior threads only leave a minimal amount of wall thickness to work on this tube. So, you should mount it in a drill vice, and do the drill and tap work on a drill press. It is not easy to drill and tap the inner threads free hand. Bevel one end of the gas tube, before running your die down its exterior.

    Some sellers list actual inside and outside diameters of their tubing; others do not. 6x4mm tube ends up will not support both internal and external thread M6x1 thread; you must stop the exterior thread short of the tube’s forward end with internal threads. You will then have to be able to remove the mounting plate, in order to clean the gas orifice, so the plate must be screwed in place on the funnel’s flange.

    If you use a silver braze alloy with as high a melting range as you can find, along with black flux that is rated for stainless-steel, this will provide a high temperature bond that requires less care to be kept in place, while brazing a hose barb on its end, with easy flow silver brazing wire and a lower temperature rated flux. Water-soaked rags, or blocking putty (ex. Wetrag) around the part, but kept away from the second area being joined, is another way to help protect existing silver brazed joints. Anti-flux can be placed around a joined area that is too close to the new joint for blocking putty to be used effectively; by resisting fluid flow out of the area of an existing join, it will help you to protect it, while brazing the second join, if you waste no time.

Note: Buy all-thread that is long enough to trap the funnel and mixing tube, or collar securely centered on the gas tube’s mounting plate, and then to make sure the mounting plate and attached gas tube are positioned centered and axially true to the mixing tube, before silver brazing.

5/16” Hose barbs for 6mm and 1/4” tube: After all other parts of the gas assembly are mounted on the burner, silver-braze, silver-solder, or glue the other end of the gas tube into a hose barb. 5/16” hose barbs will slide onto 6mm and ¼” tubes for brazing, soldering, or gluing to it. 5/16” hose barbs are the optimal size for use on 1/4” rubber hose.

 ¼” Hose barb for 6mm and 1/4” tube:  Barbed hose coupling sizes match the outer diameter of the narrowest portion of the barb; this leaves no room for threads of those same diameter. 6x4mm tubing are 0.014” smaller ¼”. Therefore, these couplings can be threaded to match up with M6x1 thread on 6x4mm tube, only through their thickest sections. 5/16” size barbed couplings can easily be silver brazed, silver soldered, or glued onto 6x4mm tube.

Copper fittings for ¼” copper refrigeration tubing have 6.35mm openings; making them perfect for brazing, or soldering 6mm and 1/4" brass tubes together to make short radius right angle joints, when plumbing fan-induced burners. Buy these fittings online, or down at your local hardware store. Copper fittings are also the obvious choice to join copper refrigerator tubing to brass tubing, both in burner construction, and to plumb between idler circuits and burners on forges.

Note: Hard rubber tubing is at least semi-insulating, which is why it is used over metal refrigerant pipes on industrial equipment. Copper is a conductor, which is my main objection to its use in burner plumbing. I want the incoming cold fuel gas to help cool the burner's mixing tube, as a safety measure. However, that same rubber tubing can be slit, and used to cover copper refrigeration tubing, with a little help from electrical tape.

[Mikey98118]

Burner sizes: The first thing you must decide about your burner is what size it is going to be. Home-built burner sizes are given according to schedule #40 pipe sizes (or equivalent inside diameters in round tubing), used as the burner’s mixing tube, because these burners were built from pipe for many years (and most still are). So, it is handy to know what actual inside diameters these nominal pipe sizes have, since it is the inside diameter, you are trying to match in a gas orifice diameter size, and to whatever you use for a conical air entrance.

    Actual pipe diameters are larger than nominal pipe sizes, both outside and inside. If you choose tubing instead, it will seldom be an exact match with pipe, so choose a little larger inside diameter, when possible (rather than a little smaller), for your burner’s mixing tube. Metric stainless-steel tube can be a handy alternative to fractional tube in the smaller sizes, and is more likely to match up well with most stainless-steel funnel shapes, because while they are advertised in inches, nearly all of them are made with metric dimensions.

 Schedule #40 pipe dimensions:                    Nearest metric tube equivalents:

(A) 1/8” pipe is 0.405” O.D. x 0.270” I.D.      10mm (0.390”) O.D. x 8mm (0.312”) I.D.              

(B) 1/4” pipe is 0.540” O.D. x 0.364” I.D.      12mm (0.468”) O.D.  x 10mm (0.390”) I.D.

(C) 3/8” pipe is 0.675” O.D. x 0.493” I.D.       14mm (0.546”) O.D. x 12mm (0.468”) I.D.

(D) 1/2” pipe is 0.840” O.D. x 0.622” I.D.     18mm (0.702”) O.D. x 16mm (0.624”) I.D.

(E) 3/4” pipe is 1.050” O.D. x 0.824” I.D.      Use pipe nipples, couplers, & round tube.

(F) 1” pipe is 1.315” O.D. x 1.049” I.D.          Use pipe nipples, couplers, or round tube.

(G) 1-1/4” pipe is 1.66” O.D. x 1.38” I.D.       Use pipe nipples, couplers, or round tube.

(1) A 1/8” burner is sufficient to heat 22 cubic inches on naturally aspirated burners.                       

(2) A 1/4” burner is sufficient to heat 44 cubic inches on naturally aspirated burners.                       

(3)  A 3/8” burner is sufficient to heat 88 cubic inches                       

(4) A 1/2” burner is sufficient to heat 175 cubic inches on naturally aspirated burners.                           

(5) A 3/4” burner is sufficient to heat 350 cubic inches on naturally aspirated burners.                             

(6) A 1” burner is sufficient to heat 700 cubic inches on naturally aspirated burners.

Note: “Sufficient to heat” means that the burner can raise a properly built forge interior of those cubic inches to welding heat, or melt cast iron in an equal size casting furnace. Are these figures legitimate? In fact, they are under stated; not over reaching for the best of today's burners.

[Mikey98118]

Rivnuts (AKA rivet nuts) are internally threaded rivets; they come in several different types, including round splined rivet nuts, which are what you will be using to mount externally threaded gas tubes onto metal mounting plates. Although an internally threaded tube product, they are designed to be press fit in place, through deformation, just like other rivets. The main difference is that they are designed to deformed easily enough that they can be trapped in place with wrenches. A rivet nut gun is not needed, for our purposes. These fasteners will collapse into place on thin sheet metal, or can be press fit into thick metal plate, without brazing, soldering, or gluing in position.

Materials needed to make your own fastening tool:

(A)  A bolt of the same thread size as the rivet nut, and at least long enough to accommodate the parts, and still engage all the threads on the rivet nut.

(B)  Two flat washers to sit next the head of the bolt, and provide bearing surfaces.

(C) A flange nut, drilled out to freely slide over the bolt thread; it is there to provide a spacer between the rivet nut and the bolt head, with its locking surface on the side facing the rivet head (you don’t want the rivet nut to turn in the hole).

(D)  A wrench for the flange nut, and a wrench for the bolt head

Drill a hole in the mounting plate that is as close to the rivet nut’s outside diameter as feasible. The more slop there is between the rivet nut and the hole the harder your job of riveting becomes. Slide the two flat washers onto the bolt beside its head. Slide the flange nut onto the bolt, with its locking side facing the rivet nut. Screw this assembly into the rivet nut, just hand tight. Push the rivet nut into the hole in the mounting plate. Put one wrench on the flange not and a second wrench on the bolt head. Tighten the bolt until the rivet nut is secured in the mounting plate. You can find several videos of this process on the Net.

Flange nuts: You will need a flange nut as part of your homemade rivet tool. You will also use a flange nut to secure the gas tube in axially true position on the mounting plate. Two flange nuts can be used to secure the gas tube on a mounting plate without use of a rivet nut, if need be.