Burners 101

[Mikey98118]

When cutting out rectangular air openings of pipe or tube:

Use common sense; don’t employ a large disc on a small job, or use a more

powerful tool than the work requires (ex. die grinder versus rotary tool; 2” versus1-

1/4” cutoff disc; full speed versus reduced speed); fiberglass reinforced cutoff disc  versus Dremel’s thicker #420 15/16” steel cutting discs (0.040”) to do finish work at  inside corners.

To cut rectangular air openings in pipe and tube:

Use common sense; don’t employ a large disc on a small job, or use a more

powerful tool than the work requires (ex. die grinder versus rotary tool; 2” versus1- 1/4” cutoff disc; full speed versus reduced speed); fiberglass reinforced cutoff disk  versus Dremel’s thicker #420 15/16” steel cutting discs (0.040”) to do finish work at  

inside corners.

To cut rectangular air openings in pipe and tube:

Use common sense; don’t employ a large disc on a small job, or use a more

powerful tool than the work requires (ex. die grinder versus rotary tool; 2” versus1- 1/4” cutoff disc; full speed versus reduced speed); fiberglass reinforced cutoff disk  versus Dremel’s thicker #420 15/16” steel cutting discs (0.040”) to do finish work at  

inside corners.

[Hefty]

What do you mean by de-tune, Mikey? I've seen the term many times in several of these threads but because I wasn't building my own burners at the time, I didn't pay enough attention to it.

[Mikey98118]

You will find instructions about how to tune Mikey burners in these pages. You will also find tuning instructions on how to tune "T" burners on their pages. If you think about what I just stated on tuning My burners, it becomes easy to reverse those directions to de-tune them as much as desired.

However, the smaller any burner is, the harder correctly tuning it gets, because differences in gas orifice sizes of one or two thousandths of an inch, which is negligible in a 3/4"  burner, becomes serious in a 1/4" burner. Fortunately, these differences can be offset, by changing what is normally done to tune it properly; this is all that can be done, with a finished burner.

If attention is payed to the chance that this little problem is likely to come up in the finish burner, you have the opportunity to adjust the air entrances, little by little, from less than ideal, to closer to it. The advantage of de-tuning before the fact, instead of after, is that you can get the absolute best out of that same burner. This is why we are discussing de-tuning during construction, rather than afterward; is this clear? If it isn't clear to you, it won't be to others, either.

[Frosty]

Correct me if I'm wrong Mike but I believe you're saying to choose which way a burner will need to be tuned before building. This makes it much easier to tune after it's built if you know in advance it will burn too rich or too lean. 

Think of it like walking in the woods, always aim for one side of the target so you'll know which way to turn when you reach the closest landmark, say lake, road, trail, etc. If you're in the woods it keeps you from walking in circles or back and forth looking for the right way to turn. 

Another good reason to de-tune a burner is to control the atmosphere in the forge/furnace, etc. This is the main benefit of building a burner with a choke. You deliberately make it to burn lean and choke it to neutral in common use. However there are situations where the extra heat of an oxidizing flame is preferable though not so much for blacksmithing. Or you can cause it to run rich to aid in welding and brazing.

You can in fact make a burner run so rich it will reduce rusty steel to clean steel. Do NOT do this indoors! you will have just made your burner into a carbon monoxide generator, it is the carbon monoxide that converts iron oxide into iron. 

Frosty The Lucky.

[Irondragon Forge ClayWorks]

If memory serves me, that is what happened when we built our forge. The Gaco 750 burner came with a .0625 orifice, which proved to be way too large running so rich, by changing the jet to .035 brought it right into an adjustable range using the choke.

I can't control the wind, all I can do is adjust my sails. ~ Semper Paratus

[Mikey98118]

1 hour ago, Frosty said:

Correct me if I'm wrong Mike but I believe you're saying to choose which way a burner will need to be tuned before building. This makes it much easier to tune after it's built if you know in advance it will burn too rich or too lean. 

Yes, generally that is it. Of course each burner design will very somewhat in its particulars. But, yes, adjusting building details during construction will make little Mikey burners behave better (the naughty little scamps)

On the other hand, small linear burners naturally have wider turn-down ranges to begin with, so less problems needing adjustment during construction. As stated, burner designs vary in the particulars.

[Hefty]

So, de-tuning is intentionally aiming for too lean or too rich to compensate for other factors that would push the flame of the finished burner too far to the other side of neutral?

[Mikey98118]

It can be used this way, and might need to be if, for instance,  a person could not get the right size needle, capillary tube, etc. to run the burner properly. With 3/8" Mikey burners, mounting an over long gas orifice, and then sanding the tube shorter will suffice to fine tune the burner. But, this may not be sufficient to fine tune a 1/4" burner. Then, further de-tuning is more easily accomplished by  gradually improving the size and/or shape of air entrances. The point is that both of these changes can be accomplished gradually, while checking how those changes are affecting its flame. Look back through the pages to see other examples of other peoples take of 1/4" Mikey burners, paying close attention to their air opening sizes and shapes.

I have twice built perfect 1/4" Mikey burners; both of them had very short turn-down ranges. Two different guys on this group have built imperfect 1/4" Mikey burners with much wider flame adjustment; I prefer theirs to mine! I don't know any way to make what I mean any plainer.

[Mikey98118]

19 hours ago, Mikey98118 said:

Then, further de-tuning is more easily accomplished by  gradually improving the size and/or shape of air entrances.

In gradually improving the size and shape of deliberately rounded and/or undersized air entrances.

[Mikey98118]

Resin bonded friction discs meant for cutting ferrous metals are usually fiberglass reinforced (with the single exception of Dremel 420 cutoff discs), and that should be stated in their sales literature. Why is fiberglass reinforcement so important? Because, without it, discs are too easily shattered; the difference is enough that none reinforced cutoff discs over 15/16” diameter are disappearing from the market. Also, discs used for steel cutting should have course grit. If you cannot plainly see the grit in expanded views of the product, keep on looking elsewhere. The difference between Dremel's #420 discs and other 15/16” diameter discs, which are only meant to cut on gold and silver jewelry, is thickness; #420 discs are 0.040” thick, while standard jewelers discs are only 0.029” thick. The thicker discs, if used carefully, will cut steel. But not the thinner discs. However, there are now 1/16” X 15/16” discs being offered by Walfront on Amazon.com for $7.08. Just input “36Pcs Resin Cutting Disc Cutting Wheel” to bring up their ad.

These are the size discs you want to employ in cutting out those twelve inside corners on a Mikey burner, and other ticklish cutting jobs.

[Mikey98118]

Fiberglass reinforced cutoff discs come in a variety of thickness and diameters; they also come with various size arbor holes: 1/16”; 1/8”; 1/4”; and 3/8” arbor hole sizes are all common. Each hole diameter requires a different mandrel. Diamond coated cutoff discs meant to be used on rotary tools have 1/16” or 1/8” arbor holes; 1/4” and 3/8” holes were originally designed for pneumatic die grinder discs. Common disc diameters that you might use in a rotary tool or die grinder are 15/16”; 1-1/4”; and 1-1/2”.  1-1/4” rather than 1-1/2” is the most popular disc size for rotary tool use, since most rotary tools are only 160 watt models, and tend to bog down when running the larger diameter disc.

[Mikey98118]

Fiberglass reinforced cutoff discs come in a variety of thickness and diameters; they also come with various size arbor holes: 1/16”; 1/8”; 1/4”; and 3/8” arbor hole sizes are all common. Each hole diameter requires a different mandrel. Diamond coated cutoff discs meant to be used on rotary tools have 1/16” or 1/8” arbor holes; 1/4” and 3/8” holes were originally designed for pneumatic die grinder discs. Common disc diameters that you might use in a rotary tool or die grinder are 15/16”, 1-1/4”, and 1-1/2”.  1-1/4” rather than 1-1/2” is the most popular disc size for rotary tool use, since most rotary tools are only 160 watt models, and tend to bog down when running the larger diameter disc.

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. Don’t press the disc against the part. Just let the disc do the work.

(3)  Always delay actually 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 likely spots to create kickback problems.

(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; this is called a torsion kickback. 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 torsion kickbacks. 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 help avoid bumping kickbacks. Aside from cutting through the kerf from the right direction, practical relief from bumping kickbacks is provided by smaller diameter cutoff discs. Dremel’s 420 discs are an economical source of suitable small 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 too many aspects of the cut 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.

    Small (22mm; 7/8”) diameter imported diamond coated discs (which are much slower cutting than resin bonded discs) excel at precise grinding. Once your coated disc loses the diamond grit from its narrow edge, keep it around for grinding excess material back to cut lines, or sharpening high-speed steel, tungsten carbide, and silicon carbide surfaces. Diamond coated cutoff discs are good for sharpening drill bits and saw teeth; they are perfect for reshaping and reducing silicon carbide grinding wheels and stones.

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, for 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 the disc to move out of alignment with the kerf, without creating kickbacks, by nearly eliminating torsional forces; you can order them online, and they are available from numerous hardware stores.

Separating discs are standard jeweler’s thin (0.029” thick) 15/16” diameter abrasive cutoff discs, which come as part of most accessory kits. They are too brittle to be practical for most steel cutting tasks, but they are a safer and surer way to cut through the last 1/8” next to a corner hole, than using a larger stronger disc; they are also better for end cuts at the forward and rear edges of air openings; especially when using an angle head attachment. Do not be discouraged when several of them shatter, one after another; they are helping with your learning curve; for the small loss of accessories of zero value to anyone but a jeweler.

    Reduce speed a little bit, and be sure to ease into cuts. Don’t bump the disc against the metal, or twist it even slightly in the kerf, or it will disintegrate. Use one of the better mandrels—not a standard jeweler’s mandrel, because even minor over-tightening from the tiny screw in a jeweler’s mandrel will shatter these discs. Better mandrels with larger screw heads will allow you to use two discs together; this also helps them to survive the work longer.

[Hefty]

Mikey, Jerry, et al,

I have built a second, slightly longer 1/4" burner (without accidentally twisting the air intake ribs) and I have some questions about slide-over step nozzles.

This is the step nozzle I'm using for these burners:

This is with quite a short overhang:

You can see the flame is shorter and the nozzle is just starting to glow a low red.

This is with a longer overhang:

The flame is longer and the nozzle is not glowing. It's hard to tell in these photos but the longer flame was also not as rich.

My question is: Is the shorter and more abrupt step making:

a) a hotter flame which is heating the nozzle more

b) a slower flame that is heating the nozzle more, or

c) is the flame burning deeper in the nozzle, heating it more? I tried to look but I couldn't really see in there very well.

I suspect it is b or c due to the abrupt step lowering pressure/velocity but I'm not sure which, or if they're the same thing. I guess that would also explain the slightly richer flame if it is slower and not inducing as much air?

Am I right, partly right, or way off?

Cheers,

Jono.

 

[Frosty]

(C,a.) The shorter adjustment is drawing less air and the flame is slower, burning inside the burner. What's burning outside the nozzle is finishing off the excess unburned fuel in the outer flame sheath. It will work fine though it's not ideal nor as hot as it can be. It's also producing more CO than is good.

The longer adjustment is inducing more combustion air, the increased amount of fuel air in the same volume (mixing tube) MUST flow faster. It is however a more neutral mix and because it's flowing faster is burning at the end of the nozzle rather than inside it. The increased amount of cool air fuel flow is also cooling the nozzle more. 

The longer adjustment is IMNSHO a more neutral and hotter flame though ideal is slightly shorter and slightly richer. Now I can't help but prefer what I like in a flame and I like a very slightly reducing (rich) flame.

The real skinny about a flame is it does NOT cause scale inside the forge. bear in mind that depending on the flame's motion in the forge can induce outside air into the chamber causing a lean atmosphere in the chamber while the burner flame is actually rich. This is true to an extent in almost any forge though Mike's thermal baffles seem to go a long way towards eliminating the effect.

Lastly the steel WILL form scale when you take it out of the forge and expose it to atmospheric oxygen so that is not an indication of burner or forge conditions.

Frosty The Lucky.

[Mikey98118]

Frosty summed things up nicely. I will only add that the second photo also shows a reducing (fuel rich flame); the difference is that it isn't heavily reducing, but what I consider lightly reducing. Many smiths prefer their burner flames set this way in a forge; I don't. But I prefer brazing with such a setting.

[Mikey98118]

The most common source for thin wall capilarry tube is hypodermic needles; these come as two different types; sharps (used on medical syringes), and blunts (used on industrial dispenser syringes). You are far better off buying dispenser needles, rather than using medical needles, because dispenser needles are much more likely to have the nominal inside diameters expected in their gauge size. Medical needles are as likely as not to be extra thick or extra thin walled, leaving you guessing about their inside diameters

.

 

Dispenser Needle sizes:

    #14 Gauge is 0.072” (1.83mm) outside diameter by 0.060” (1.54mm) inside diameter.  

    #15 Gauge is 0.065” (1.65mm) outside diameter by 0.054” (1.37mm) inside diameter.   

    #16 Gauge is 0.064” (1.63mm) outside diameter 0.047” by(1.19mm) inside diameter.      

    #18 Gauge is 0.050” (1.27mm) outside diameter by 0.034” (0.86mm) inside diameter. 

     #20 Gauge is 0.036” (0.91mm) outside diameter by 0.025” (0.63mm) inside diameter. 

    #21 Gauge is 0.033” (0.83mm) outside diameter by 0.021” (0.53mm) inside diameter. 

    #22 Gauge is 0.027” (0.70mm) outside diameter by 0.017” (0.43mm) inside diameter. 

    #23 Gauge is 0.025” (0.63mm) outside diameter by 0.014” (0.35mm) inside diameter. 

    #25 Gauge is 0.020” (0.53mm) outside diameter by 0.010” (0.25mm) inside diameter. 

    #27 Gauge is 0.016” (0.42mm) outside diameter by 0.008” (0.20mm) inside diameter. 

 

MIG contact Tip sizes:

    Tips for .023” welding wire have a .031” nominal through-hole diameter. 

    

     Tips for .025” welding wire should have a 0.034” nominal through-hole diameter.

     Make sure that you aren’t being sold .023” tips as .025” tips.

     Tips for .030” welding wire have a 0.038” nominal through-hole diameter.

      Tips for .035” welding wire have a 0.044” nominal through-hole diameter.

      Tips for .040” welding wire have a 0.048” nominal through-hole diameter.

      Tips for .045” welding wire have a 0.054” nominal through-hole diameter.

      Tips for .052” welding wire have a 0.064” nominal through-hole diameter.

      Tips for .062” welding wire have a 0.070” nominal through-hole diameter.

Just because there is a welding supply store in your town doesn’t mean that they will have the MIG tips you need in stock, or that they will bother to sell you one or two of them at a time, even if they do. Your sale is hardly worth their paperwork. You can buy MIG tips on line as few as five at a time for less money than they will cost at your local welding supply store, and chances are that the shipping charge will amount to less than the gas you may waste receiving a rotten experience, trying to buy them locally. On the other hand, you may do just fine at your local store. Some stores are starting to sell popular tip sizes in packages of five, from prominently displayed racks.

[Mikey98118]

Stainless steel tube is the easiest choice to work with for any burner tubing part (although schedule #40 steel pipe nipples from a locale hardware store is cheaper); and it is the choice that is demanded for at least the outer tube of your burner’s flame retention nozzle. Since, in either case you will be unlikely to match up that outer tube with the nozzle’s spacer ring, and then the ring with the mixing tube for a sliding fit, it is good to know that up to a 1/8” a gap between outer tube and spacer ring, or between spacer ring and mixing tube can be easily tolerated.

[Mikey98118]

Vortex Burner design principles

    Let us start by clarifying what is meant by the term “vortex burner.” Burners that swirl the flames they make are often touted as vortex burners. But causing a flame to swirl happens far too late in the air/fuel mixing process to provide much benefit; used this way, the description is mere hype.

    Vortex is a fluid dynamics term, describing a region where the flow of gas or liquid revolves around an axis line.  The vortices generated on the trailing edge of plane wings only create drag. At the other extreme, a tornado’s funnel is powerful, but only generates havoc. The gentle current of a bathtub drain effectively employs vortex flow to good purpose, and so should your burner.

    Vortex burners are simply advanced linear designs; linear burners are chosen over jet-ejector types, to supply maximal vortex motion in their air flow. Good combustion requires incoming air to mix thoroughly with a burner’s fuel gs jet. A swirling motion provides the most mixing for the least drag on your burner’s air flow.

    When incoming air passes through a constricting tubular shape (ex. pipe reducer or kitchen funnel), vortex movement is generated, becoming an excellent air/fuel mixing aid. Most successful burners, whether linear or jet-ejector, create at least some vortex flow. High-speed tube burners are an exception; they gain swirl from three (fore and aft beveled) rectangular side air entrances; nevertheless, if you place a pipe reducer between their air entrances, and a smaller diameter mixing tube, their performance will be enhanced.

   Since most successful burner designs create vortex flow, why bring it up? Because the people who designed those burners, only pictured them as swirling incoming air into a stream of fuel gas, and thought no further. Both passive and fan-induced “V” burners, are designed to enhance vortex flow, and then to derive maximum benefit from it.   

    Any device that provides lateral air movement at a funnel opening, will increase vortex flow through the funnel; this includes the two opposed air openings on “T” plumbing fixtures, disc shaped choke plates near funnel entrances, or (my favorite) impeller blades at a funnel’s entrance.

    If you strip the blades from a cheap or worn-out axial computer fan, and mount them on a linear gas pipe at a burner’s air opening, they will significantly increase vortex movement through the funnel, even though they are still, because they start lateral air movement (spin) at the funnel’s entrance, instead of within it.

    Installing axial computer fans on linear burners will supercharge vortex flow, but this requires a more complex gas assembly, and an electrical power source. So, it is easier for novices to move from passive to powered “V” burners in stages.

    Some part shapes used for air entrances on naturally aspirated linear burners, also work well with moving fan blades, while others do not. However, the limits on shape and size imposed by use of moving impeller blades, do not apply to motionless blades; these can be mounted on gas pipes without worry.  

    Straight or curved wall pipe reducers, kitchen funnels, and other constricting tubular shapes provide convenient ready-made entrances for incoming air to spiral its way through, and into the burner’s mixing tube; its ever-constricting path increases its rotational speed, along with its forward velocity (by about one-half of its rotational speed). Also, the faster the incoming air’s rotation, the lower the pressure of the incoming air flow through the mixing tube; this is all very good, but requires the mixing tube to be lengthened enough to stabilize the flame (by allowing friction within the tube to slow the mixture’s swirl and forward velocity, before it exits into the flame retention nozzle).

    Or, internal vanes near the tube’s exit can be made to slow air spin, in order to keep the mixing tube’s length shorter. A larger diameter flame retention nozzle can break the flow’s exit speed sufficiently. Thus, you would want to exchange your smaller diameter flame retention nozzle, used at lower gas pressures and fan speeds, for a larger one, when running a fan-induced burner full-out.

    The first thing 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 vortex created.

   Secondly, the shorter the length of the funnel the greater the drop in air pressure it creates at its opening. This drop in the pressure of incoming air is not sufficient to create a problem in naturally aspirated burners, but the low-pressure zone created at the opening with moving impeller blades, can draw some fuel gas back into the fan. Then, the fan’s electrical sparks will ignite the fuel/air mixture.

    So, a maximum 3:1 ratio between entrance diameter to the mixing tube’s internal diameter, becomes the first safety margin with fan-induced burners; another safety margin is provided with sufficient length in the funnel shape, or the addition of a short tube section between the funnel opening and the fan; this produces the same effect as a longer funnel shape (in avoiding back-flow of fuel gas into the fan). The SE HQ93 Stainless Steel Flask Funnel is an excellent example of such a shape being available as a safer air entrance for use on fan-induced 1/4" burners.

Note: The moving fan blades you are concerned with here are impeller blades, which have become standard on axial computer fans; not the old-style flatter blade designs that are meant to push air forward; those increase the pressure of incoming air. Impeller blades lower the pressure of incoming air.

    This leaves us wondering how long a funnel is long enough. Only experience can answer that question, but I suggest a minimum length of one and a half times the diameter of the air opening. Furthermore, fan strength, constrictor shape (straight, convex, or concave wall) all come into play. Add to that how much curvature at what point in a funnel shape, and we are reduced to trial and error. Always remember that, if the burner you design starts backfiring into its fan, there is very little work needed to change it over to a naturally aspirated design. You do not have to rebuild the whole burner.

[Hefty]

For ease of tuning a burner in a forge, can you just cast a nozzle into the liner, around some pipe/tube the same O.D. as the mix tube with a piece the same O.D. as the spacer in it's step nozzle on the end of it? And then just move the burner back and forth in the mounting system to tune?

[Another FrankenBurner]

You can.  I have, sort of.  I 3d printed a form and cast a nozzle.  Then cast the forge liner with it in place.  It ended up cracking at the connection point between the nozzle and the liner.  I now cast the liner with the right size port for the nozzle to sit flush to the liner but not be cast to it.  I use some floating nozzles and some nozzles are cast right to the mix tube.  

I appreciate my refractory nozzles.  I have melted down several stainless nozzles.  The only time I use stainless anymore is for my hand torch burners.

 

[Mikey98118]

No: Firstly,  no to the idea that casting a replacement for a flame retention nozzle will be the easy path; it certainly will not, and the smaller the nozzle being replaced the trickier that will be to do right.

Next; no to the idea that tuning a high speed tube burner in the forge, by how far forward the mixing tube is placed in a built-in refractory nozzle will be easier than tuning than such a burner, with a slide-over stepped nozzle out out in the open air.

I'm not trying to hamper you in moving to such a system, for it does have many pluses; but easier tuning of a high speed burner, just isn't among them

I don't think that imprvement of this burner will be found at this end; look into change the gas orifice, if you want more heat.

 

5 minutes ago, Another FrankenBurner said:

I appreciate my refractory nozzles.  I have melted down several stainless nozzles.  The only time I use stainless anymore is for my hand torch burners.

As I said, there are real pluses; here is one

Another is avoiding the cost of stainless steel tubing (a specially with larger burners), which is becoming serious, in a part that must be replaced every few months.

[Hefty]

Yes, I worded my question poorly. "Easier" was not the right choice. I meant more like: to avoid burning up small nozzles, could I cast the nozzle into the liner?

I fully acknowledge that this would not be easier than tuning a burner by itself with a slide over stepped nozzle.

6 hours ago, Another FrankenBurner said:

You can.  I have, sort of.  I 3d printed a form and cast a nozzle. 

Yes, that cast liner is part of the inspiration for this line of questioning. I've gone from building one small burner for use as a torch to building another two with the intention of making a mini-forge and I have some ideas for a cast liner using two sizes of PVC pipe and some layers of laser cut plastic to cast the end faces so the ceramic fibre insulation can just wrap around it and I can rigidise it and then secure the shell around it.

I may still play with the nozzle cast into the liner idea, but if not, I just need to leave a large enough hole in the liner to allow the nozzle to fit easily and stop just before the level of the inside of the liner itself? Sorry, I just did a quick search and I'm asking an answered question but I have a habit of paraphrasing things into questions to ask for clarification.

[Another FrankenBurner]

That was the order I used. Cast the liner, wrap with layer of blanket, rigidise, wrap second layer, rigidise, skin it all with metal, give it some plistix.

If the nozzle is floating, the hole needs to be just smaller than the nozzle OD to act as a shelf. If the nozzle is mounted to the mix tube, the hole can be larger. 

If you are using a refractory nozzle, it can bump up to the forge liner. If you are using a metal nozzle, it will survive longer if it is further from the heat. If you armor the blanket with refractory in the burner port all the way to the shell, the tip of the metal nozzle can be just inside the shell. Doing so gets it back from the heat and allows ambient air to passively cool the nozzle. It also pulls the flame further back to help prevent direct impingement on your work which is more likely in a mini forge. 

[Hefty]

If I line the port all the way to the shell and put the burner just inside, won't this act like a bigger nozzle and affect the flame? Or is this not a problem of the port is big enough?

[Mikey98118]

Treat this area just like you would a regular stepped flame retention nozzle for length, diameter, and shape. Any additional length beyond the equal of the inside diameter, which should be about two pipe sizes larger than the mixing tube, plus an additional 1/8" in length, should increase at about a 30 degree taper, to keep it from affecting the flame.