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MIG Welding tips in Gas Burner?


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I've been using Michael Porter's Gas Burners for Forges, Furnaces, and Kilns as plans to build my gas forge and burner. The plans recommend I use a Tweco .030 or .035 inch MIG welding contact tip, 1-1/2-inch long. I have no experience with these parts, and have no idea what the importance is of the length, the taper, etc, and I've been unable to find this part anywhere. The drawings in my plans show a tapered MIG tip (shown in attachment), but I've had difficulty finding anyone who carries any contact tips with tapers. Most parts I've been able to find have a rounded end. 

Does the overall length of the MIG tip, the inside diameter, and the taper on the end affect performance? If not, I'll just buy one that I can find readily, and not have to go searching for this exact piece.

Screen Shot 2015-09-05 at 11.28.40.png

Edited by JPVT
Forgot the attachment!
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If I didn't welcome you aboard earlier glad to have you here.

If you're going to use someone's plans then follow them as closely as possible. Mike Porter's burners work very well his type 4 is probably at the point of diminishing returns for tweaking the design.

One of his main design philosophies emphasizes a laminar air fuel flow in the tube so all his burner features are intended to enhance laminar flow. The tapered mig tip is to reduce or eliminate cavitation where the air flow moves over the blunt tip.

A welding supply should carry tapered tips, call and ask. This is exactly the situation where going to a web site fails, a human voice on the other end can figure out what you want even if you aren't clear about what you're asking for.

Just ask for tapered mig Contact tips, putting "contact" in the name will help eliminate confusion.

Whether Mikey is right about laminar flow or not I don't know, I design for good turbulence to enhance fuel air mixing as propane doesn't mix well with others. Do NOT try to incorporate any of my ideas to a Porter burner or a Reil, or a Side arm or . . . their's to mine, mixing and matching is more PITA than useful. They all may be essentially the same in principle but execution is different and will alter how they work. Just following the plans you've chosen will give you the best results.

Frosty The Lucky.

 

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I used the same plans making my burners. I also couldn't find the tips suggested. I'd assumed that they were a us thing. I went with standard might tips. The first few I filled them to shape. I now used them as they come, and find it makes no noticible difference.

Andrew

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I can't comment on how it effects performance, I know what Mike intended and also know he had some pretty sophisticated instrumentation set up so he may have been splitting hairs by that point. Ron Reil got onto the highly efficient path too and was doing everything he could to squeeze as much performance as he could from his designs.

I just went for simple, easy and good enough. My lack of precision is undoubtedly why all 4 burners on my shop forge are a little different including the one golden bullet that tends to melt hard fire brick.

When Mike, Ron and I talk we don't discuss burners, they all work and work well. It'd be like the Ford Chevy debate.

Frosty The Lucky.

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  • 3 months later...

Any 1-1/2" long MIG tip can be inserted into a drill and spun under a hand file. "Presto, chango"; you got a tapered tip. Don't affempt to file the tip end down to a point; leave about a  1/16" around the orifice.

There is even an exception to the tip length requirement. Larry Zoeller exchanged  the recommended schedule #40 1/8" gas pipe for a schedule #80 pipe, so that he could tap thread directly into the pipe without silver brazing an insert into it, and found as a side benefit that 1" long MIG tips now worked just fine. I tried out Larry's changes, and they DO work just fine. You can order these pipes from Larry Zoeller forge, or from McMaster Carr.

The likely reason you're being lied to at regular welding supply stores is that  the sale of a single MIG tip doesn't even justify their paperwork. When you order the tips online, they aren't sold singly. So call the welding supply store and ask if they have them in stock and will sell you THREE  tips at a time; otherwise you get to pay shipping charges for online  purchases. After the book came out I got a lot of angry claims that this tip wasn't available at local welding supply stores; and now you know why.

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Here in Wasilla Alaska where shipping nearly double the price of everything a bag of 10 mig contact tips runs about $14.00. Short, long or tapered run about the same. If you have a buddy working there a singleton MIGHT fall on your foot but don't count on it.

Frosty The Lucky.

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For the people who don't believe they can find the recommended MIG tip:

You can also employ a Luer-lock dispenser needle, with the recommended orifice size, on a Luer-lock adapter (AKA a plug; this is the needle to connection fitting you need); they come in both nickle plated brass (economical) and stainless steel ($$$). McMaster Carr carries them, as does Vita Needle, and other online sources. The adapters come in various popular thread sizes, including 1/8" male pipe thread. By swhitching out the 1/4-28 tap for a 1/8" pipe thread tap, you can run the needed thread directly into standard schedule #40 1/8" pipe that is available at your local hardware store. Look up the actual orifice diameter of the recommended MIG tip; not its call-out size, which is listed for the welding wire diameter each tip is supposed to run.

Warning: Do not use Luer-lock needles or adapters with plastic bases; they might melt, and turn your forge into a flamethrower!

An .023" MIG contact tip feeds that size wire  in a MIG gun, but its actual orifice size (AKA inside diameter) is .031"; this isn't the optimal orifice for a burner made with 1/2" schedule #40 pipe; just the smallest size MIG tip available. The optimal orifice is .028". Needles are usually listed by gauge size, which is nearly useless to you, because gauge size  has to do with their outside diameters, but needles come in heavy, medium, and thin wall versions. So, look for the inside diameter before buying.

Where two different MIG tip sizes are listed in the book, this means that one is a touch too small, and the other a touch too large. Look up the actual orifice size for them on page 22, split the difference, and look for that inside diameter, or as close as you can get to it, in your dispenser needle.

Those of you who did find the right size and length MIG tips, can also use the optimal orifice size by inserting a dispenser needle into a MIG tip with close to the right size hole to match the needle's outside diameter, by bending a curve into the needle, and then cutting off the protruding portion of needle; next, use very fine sandpaper, a bit of spit, and a circular motion to remove any internal burr from grinding the needle apart; torch tip cleaners will also work for this job, but are more difficult to employ.

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Finally, Luer-lock needles are superior to MIG tips in smaller burners (3/8" and under) because they are too thin fo enterfere with laminar air flow past them.

JPTV,

A lot more research has been done since that book was published: you have perfect access to its author, but I can't answer questions that you don't ask.

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It is only mentioned in the updated version due out next year, but I've modified my original advise about employing 4-1/2" angle grinders for all the work, to include hand held rotary tools for cutting out the air openings. In 2004 these tools and their accessories were just too expensive for most of the starving artists the book was dedicated to; today this isn't true. If you feel that both tools are too great an expense, choose the rotary tool over the angle grinder. Also Dremel's 1-1/2" spring loaded EZ mandrel, unlike much of their overpriced stuff, is worth every penny on this kind of work.

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Existing tin cans make nice cheap furnace shells, with built in bottoms, which makes them pretty irresistible for first time builders of portable forges and furnaces. When someone mentions making a shell from light sheet metal and pop riveting it together for more convenient diameters, most of us just shrug off the suggestion. But recently I stumbled across double wall chimney inserts that are filled with...you guessed it; ceramic fiber. Naturally they are too expensive to be very tempting, but they got me to thinking...
    Two different diameters of sheet metal pop riveted together could be filled with Perlite that is glued together with Rigidizer, making a highly insulating and quite rigid furnace shell for a minor monetary output. And since such cylinders can be made into larger diameters than the usual shell sources, they could also contain an extra layer of insulation and still have plenty of room left inside for hot-face and insulation layers.
    Of course the builder doesn't need to use a tubular shape; this kind of shell would also lend itself nicely to oval body forges...light sheet metal can easily be cut tp any desired shape for front and rear faces. By making the outline and then a larger outline 1/2" beyond and parallel to it room can be left to cut in tab shapes with a rotary tool, which can then be bent 90 degrees, and later drilled, with the part in place, holes can be drilled through end piece and  outer shell wall beneath; they can be pop riveted in place, making the shell quite a rigid form to  add the insulation into; afterward this form is little heavier than a simple tin can, but much tougher.

Burner ports can be attached to the finished form by employing a hole saw, to drill through both walls at the desired angle, forming four drilled tabs on one end  of the tube, shoving the tube through the holes from inside the shell, drilling matching holes through it, and employing pop rivets or sheet metal screws to hold them in place. With the tubes penetrating two separated sheet metal walls, the burners will also be held rigidly in position.

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Rigidizer is nothing more than fumed silica, which is a colloidal substance, witch means that it stays suspended in water, unless it's allowed to freeze. A little ordinary food coloring is added to enable you to see how far it has penetrated into the ceramic fiber layers. Purchased from a pottery supply, it's expensive, and costs a lot to ship, since it comes already mixed into water. Purchased online it is cheap and sells for a song, because it is feather light; buy fumed silica, a plastic jug, and swipe some of the wife's food coloring; mix up you own Rigidizer, and save a pile of money.

Perlite also costs very little, when bought by the bagful from the garden department of large hardware stores

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Hybrid pipe/refractory flame nozzles: You can build a flame nozzle that is a compromise between S.S. nozzles and refractory blocks. Using oversize thick tube or schedule #40 mild steel pipe to provide enough material to securely mount set screws in;. You can save a lot of money on materials cost when building nozzles for larger burners this way. You also gain the ability to use propylene and/or oxygen enrichment to increase flame temperatures far higher than any mere metallic nozzle could withstand. The refractory interior helps keep the metal shell from collapsing at top heat, while the shell holds the refractory nozzle on your burner, so that more than one nozzle diameter can be employed, while refractory wear and tear is easily repaired, or the hot-face replaced; unlike the case with refractory burner blocks. High heat castable refractories can be used as the hot-face layer, while ceramic fiber blanket can be placed between the hot-face and stainless steel shell; this blanket helps insulate the shell from the superheated refractory hot-face inner layer. The springy blanket also helps seal the nozzle, so that six screws can continue to be used to hold the nozzle assembly centered and parallel on the burner, rather than constructing a work intensive fitting on the nozzle’s rear.

 

what makes this nozzle workable for direct exposure to the flame is additives like Rigidizer, and high heat mortars like Sairset, which can act as a hot-face surface and are easily repaired from flame damage.

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17 hours ago, Mikey98118 said:

Hybrid pipe/refractory flame nozzles: You can build a flame nozzle that is a compromise between S.S. nozzles and refractory blocks. Using oversize thick tube or schedule #40 mild steel pipe to provide enough material to securely mount set screws in;. You can save a lot of money on materials cost when building nozzles for larger burners this way. You also gain the ability to use propylene and/or oxygen enrichment to increase flame temperatures far higher than any mere metallic nozzle could withstand. The refractory interior helps keep the metal shell from collapsing at top heat, while the shell holds the refractory nozzle on your burner, so that more than one nozzle diameter can be employed, while refractory wear and tear is easily repaired, or the hot-face replaced; unlike the case with refractory burner blocks. High heat castable refractories can be used as the hot-face layer, while ceramic fiber blanket can be placed between the hot-face and stainless steel shell; this blanket helps insulate the shell from the superheated refractory hot-face inner layer. The springy blanket also helps seal the nozzle, so that six screws can continue to be used to hold the nozzle assembly centered and parallel on the burner, rather than constructing a work intensive fitting on the nozzle’s rear.

 

what makes this nozzle workable for direct exposure to the flame is additives like Rigidizer, and high heat mortars like Sairset, which can act as a hot-face surface and are easily repaired from flame damage.

This is an excellent summary of one of the ways that I solve the problem for my self.   My first welding forge used High temp fire brick that I cut/drilled to form an expansion nozzle. It was a tedious chore but for an experimenter not big deal. 

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On 12/23/2015 at 2:21 PM, Mikey98118 said:

MIG tip tapering makes a lot of difference in smaller burner diameters and no difference in large burners.

The easy way to shape fire brick for a flared nozzle is to first use a hole saw a bit larger on the OD than the large end of the taper. Use either an old disposable or one for tile to drill the basic hole. The tricky part is getting the taper right, the 12:1 ratio is the MAX rate of expansion that will allow a smooth or laminar flow, less is fine. If you have a wood lathe just turn a wooden plug to your desired taper. Once again I use my hole saw to make my "blank". The piece of wood you have to dig out of your hole saw has a perfectly centered hole and lacking a wood lathe a strong rugged duty electric drill will serve as a lathe.

To chuck the wood plug (blank) in the drill simply run a bolt the same diameter as the pilot hole through it and using washers and a nut secure it tightly. You can chuck the hex end of the bolt in the drill chuck and let the threaded free end rest on a guide block so it doesn't deflect. You can make the tail stock easily by putting a drill bit in the mounted drill and sliding the wood block into it. Then with the blank chucked into the drill slide the tail stock block over the threaded end and clamp or duct tape it down.

If you use a hand drill you need to clamp it down securely and remember the bearings in the drill are NOT thrust bearings so they won't stand up to much side loading so you can't just take a chisel to the wood like it's a real lathe. If you set up a guide, say two tapered stops on either side of the wood blank then just letting a wood rasp ride on the turning wood plug will make a fine tapered form.

Once you're turned your tapered plug apply abrasives, contact cement and sand paper is nice just make sure there is a little overlap in the direction it turns so it doesn't just peal the sand paper off. Another more permanent method is just glue sand to the tapered plug.

Make sure the threaded end of the shank (bolt) is at the narrow end of the . . . (sanding die?) and long enough to reach through the fire brick. Chuck in in your hand drill and sand the hole into a tapered flare.

Really, it's easier to do than describe here.

Frosty The Lucky.

 

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Once you build or buy a  burner, you'll want to install it in a forge or furnace, which brings us to burner ports. Some people just drill a hole in the steel shell and form a matching hole in the refractory, but this doesn't provide support for the burner or any way to fine tune its aim within the equipment, so others attach a short length of pipe or heavy wall tube, and use six thumb screws, in two rows of three screws each, to trap and aim the burner.    

    So much for the obvious. Now let's discuss control of secondary air, and cooling of the burner. Even single combustion wave burners can benefit from external cooling air, if the burners penetrate extra thick refractory and insulating layers (more than 2") or are vary small 1/4" or less, because internal cooling from the cold incoming propane could be overcome during very long heats, under these conditions.

     Most burners have at least primary and secondary flame envelopes, so some builders deliberately leave their burner ports unsealed during operation, because secondary air induction (now powered by the flame) is needed for complete combustion. Unfortunately, this nearly always leads to an overabundance of a good thing, because the flame becomes an even more powerful induction "motor" than a burner's gas jet makes. It takes energy to heat air, so extra secondary air becomes a drag on performance within the equipment; typically a 20% heat reduction. Fortunately, we don't have an if/or choice to make. It is just as easy to control incoming air through the burner port as incoming air through the burner.

     First, add another choke at the end of the burner port's tube; mount a washer brazed to a ring with thumb screw on the burner; once the burner is installed, it can be slid up against the portal tube's end to seal the port when needed, and moved away from the opening to varied distances, as desired to control secondary air flow.  Is this more work? Obviously; should you expend the additional effort? Also obviously.

     But what about single combustion wave burners? Better to have a way to cool down the burner when needed, than to depend on luck. If your burner suddenly starts back firing you won't care about temporarily losing some furnace efficiency, so use the same burner port changes for them too.

     Also if a Mikey burner isn't perfectly made, and perfectly tuned, you will need a very little bit of secondary air for complete combustion in a forge or casting furnace; better to have it than risk even trace amounts of carbon monoxide in your shop.

 


 

 

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Why use exterior baffle plates or walls of brick, instead of partially enclosing the forge front and back openings?
There isn't any such thing as an optimum hole size from an exhaust vent. Too large and you waste energy; too small and you apply back pressure against the burner. If you figured out some mathematical formula to come up with the right vent size for a given burner, you'd still be out of luck, because most burners have a turn long down range. If the burner and vent hole match at one setting the hole is either too large or too small at every other setting.
    Fortunately, there isn't any need to make an exhaust vent; just use a variable distance baffle plate made from a high alumina kiln shelf (or stack of bricks) instead, and you can adjust your forge exhaust opening to perfectly match any burner size or setting. an exterior baffle also permits recovery of radiant heat that would otherwise be lost, reduction in noise (as sound waves don't turn corners very well), and hot exhaust gases are directed up and away from the smith.
    You might ask "if this system is so perfect why isn't everybody using it already?" I would answer "for the simple reason that most people feel that good enough is good enough; and they are right...so far is that goes. On the other hand, when you are building a forge from scratch this isn't more work; it's just a different design path.

 

 

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Your last paragraph got me smiling there Mike.  I so fit into the good enough is good eough category. 

To address the question of why we all aren't using the "perfect" forge. I'd have to say they're kind of expensive for folk who aren't dong this all the time or believe me I'd HAVE an induction forge!

Frosty The Lucky.

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44 minutes ago, Frosty said:

 

To address the question of why we all aren't using the "perfect" forge. I'd have to say they're kind of expensive for folk who aren't dong this all the time or believe me I'd HAVE an induction forge!

Frosty The Lucky.

:) "perfect forge" for what? Jup my induction is just the biscuit most of the time! It's fantastic to think I need to taper this , flick the switches and seconds later be whacking hot steel.

Then end of the month comes and the bill arrives, "jeepers I've got to finish that woodgas powered genset" thought floods my mind!  I recon the setting up of the forge related to 'your' work can usually get you close to the 'ideal' forge . For hammer production(multiples) a larger forge with a ribbon burner is IMHO is more efficient but on 1/2" round bar not at all etc.

You've just got to collect a number of forges! :) That said, I believe I have a fantastic charcoal retort that makes beautiful charcoal that I now use for terra preta as I can't remember when I last used charcoal to forge with? I've been asked about selling my charcoal forge but alas 'nostalgia ' has prevented me from doing so.

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