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Two-Brick Forge Advice

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Andrew C, TP, and Frosty: you're right. Two things going on here, one is I left the MIG tip way too long and two is the flare fitting protrudes too deep into the tee. I plan on cutting the MIG tip to length once I have a nozzle so I can look at the flame and cut little by little. (My nozzle will be cut from the forge wall, per Tristan's instructions.) As far as the flare fitting being too deep, yeah I just noticed that. Since it's not under pressure, I'm going to back it out and use some red loctite. The trick will be keeping it centered.

Frosty, I did order some 3/4 x 1/2 tees as well, they just haven't shown up yet. I figured I'd try both and compare, since Tristan had success with the 1/2 x 1/2. I hear what you're saying about more intake area = more induced air.

To your point Frosty, one thing I'll say to anyone using a 1/4" flare to hold the MIG tip: tap the 7/16-20 hole as little as you can. The mig tip sticks out an extra 1/4" past the threads because of the flare. As you can see in my pictures, the back of the MIG tip is almost halfway down the tee.

Sorry my process is so disorganized. I'm still figuring some things out as I go. I'll try and make a clean summary when I'm done.

Edit: I just had a serious facepalm moment. I can just cut the 1/4" flare fitting shorter!! D'oh!!

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Frosty I'm a bit confused what you mean by using the pilot drill as a go no go gage for the brass fitting. Are you saying there's a way to use the drill bit to gage how far the fitting will thread into the tapped hole? I could kind of see how you might be able to use a pipe tap to tell how far an NPT fitting will go in because they're tapered, but with a flare fitting the threads aren't tapered so I don't see how you could use a gage.

I've got more tees and fittings to play with now. Now I've got both 3/4 x 1/2 and 1/2 x 1/2 tees. I forgot to buy a prick punch though. Shucks!

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Alright, got a 3/4 x 1/2 tee ready. Pretty much hit the same tolerances as with my 1/2 x 1/2 attempt. Missed the casting seam by 1/32.


I also cut off the flare on the flare fitting, shown above. Used a different jig to drill it out more:


(Note: if I was smarter, I would've gotten a 1/2" hex nipple to use to affix the tee while I drilled that out instead of my terrible drill press vise)

The back of the mig tip is now close enough to the back wall of the tee that I can cut the mig tip to roughly 1/4" away (Frosty's ratio) from the mixing tube


(Note: I do not intend to leave the mig tip this long.)

Now I'm waiting on the bricks so I can observe the flame and tune. Those are expected tomorrow.

One thing has dawned on me tonight. If you're a master of patience and have nice scribe, punch, and drill bit, you could probably hit 1/64" with a benchtop drill press and cheap drill press vise like I use. If you want to get below 1/64 accuracy, I feel like you need a drill press vice with cross-feed (only need one axis for this task). Of course, a vise with a sloppy cross-feed is equally useless, perhaps worse. Using the flange seems to work pretty well, but I lack the tooling to measure how good the 90* angle is. (I couldn't tell you how much 1/32 or 1/64 will hurt burner performance. I leave that to the experts.) The next biggest barrier I think you'll run into is how sturdy the table on your drill press is. Mine flexes a little bit.

Edit: one thing I've been doing but forgot to mention is that I've been consistently deburring and cleaning out chips from the inside of the brass fitting with compressed air. A brass chip can easily clog the mig tip.

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By pilot drill I'm referring to the drill bit you use to make the hole to tap. Use the shank end to test brass fittings so you can tap them. Make more sense?

I don't use my drill vise at all when making T burners, I clamp the floor flange to the drill table and do NOT move it. 

Here's a trick for center punching the T. first measure center and mark it, screw it onto the close nipple and floor flange, really snug but not pipe wrench tight! Then put a center punch in the drill press and carefully slide the T & floor flange jig until the mark and point of the punch connect now give it a gentle bump with the feed lever. Now put the jigged T (T mounted in the jig) on a bench or anvil and center punch it. You'll be able to feel the punch mark made in the drill press. When I say GENTLE BUMP I mean gentle, you do not want to damage your drill press, they are NOT made as impact tools. You can get away with a little though.

After the T is center punched put the punch back in the drill chuck. Using the drill press to hold the T in position by pressing the punch into the center punched mark you can clamp it down and it's aligned and centered. This method makes 1/64th. slop. 

Make sense?

You can use 1/4" schedule 80 pipe instead of the brass fitting. The ID (Inside Dimension) is just about perfect to tap for a mig tip. You can then thread the outside of the pipe tap the burner T to match. A lock nut prevents the pipe from moving, You can fine tune by screwing the pipe w/mig tip in or out and lock it with the nut.

You can also put a thin lock nut on the brass fitting to space it farther out. Drill and tap a piece of thin steel if you can't find thin nuts.


Frosty The Lucky.

Frosty The Lucky.

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Holy smokes Frosty. That's really helpful!

The center punch trick with the drill press is a game changer. Thank you!!!

And yeah, I'm going to remember to buy a 1/2" hex nipple today so I can use just the floor flange. I really don't trust my vise any more, but I can see why someone with a good vise like Tristan's would prefer it.

Also yes, I see what you mean now about using the pilot drill bit shank as a gage. I'd been following the tap chart, and that seems to have worked fine.

I like the idea of making a lock nut. I have some 3/16 plate lying around. If I run into any problems with the 1/4" flare fitting, the schedule 80 1/4" nipple is what I'll try next.

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On 1/13/2021 at 10:57 AM, Frosty said:

Were 3/4" x 1/2" Ts unavailable, or what is your reasoning for using 1/2" x 1/2"? If you're concerned about not having as much air available due to altitude I don't understand why you'd use a T that can't supply as much.

Tristan has a lot more experience making 1/2" burners than I do so if you have to decide, go with his advice.

Let's not lose sight of the fact that this whole idea of building a T burner like this was Frosty's idea... I would defer to him...   

Sorry you had issues getting them straight, it's not an easy thing to do. Even with a lathe it is possible to screw them up though, so don't feel bad. 

I usually use the 1/2x1/2 as they are easy for me to get and I am used to tuning them. If I was at 5500' I would use a 3/4x 1/2 as well.  I have noticed that typically on a 3/4x1/2 the tip of the MIG end is above the 1/2 way mark of the 3/4 opening. Using 1/2x1/2 I need to be below that halfway mark to get them running good.  That is just to get you in the ballpark. I am attaching a photo of the area I am talking about.  On the plus side you now have experience drilling and tapping T's so a change is going to be easier for you.



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Thanks Tristan for the pointers! I'll definitely switch to 1/2 x 3/4. Didn't realize the 1/2" air intake was just out of convenience.

I used to have access to a really nice metalworking lathe on campus before covid times (a mill too! those were the days). Now keycard access is tighter. I can use my landlord's wood lathe when he's not using it, but I didn't bother because I don't know what kind of accuracy to expect from the tailstock alignment, and I worry I'll chew up the chuck jaws holding a steel part under load.

Bought myself a 1/4" prick punch and a fresh 1/4" center punch, and a 1/2" short nipple so I can use a floor flange now.

Tristan, when you do get another chance to follow up, I'd be curious to know how you fit the hole saw through all 9" of brick. I'd definitely bottom out any of the drills I can think of. Did you chase it from both sides? Also, what did you use to scoop out the center? And lastly, what tool did you use to cut the flare into the brick?

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So tonight I tried using the floor flange instead of a vise, and using the drill press to center punch before drilling. First attempt was way off, 3/64" off the casting seam and 1/32" to the side. The initial center punch mark was in the correct place, the 25/64 jobber bit wandered off that mark. What I found was that the drill bit wobbled, I suspect because of slop in the chuck jaws. I'm guessing that my center punch mark wasn't deep enough to coax the drill bit, and it slid off the casting seam. It was initially aligned with the center punch mark when I started drilling.

On the second attempt, I kept everything clamped up until center punching. After I made a little dent with the drill press, I took the flange off the drill table, so I could hammer a deeper center punch mark into it, so it would be comparable to the depth of the mark I had on last night's attempt. I then put it back on the drill press, and re-aligned the chuck with the center punch mark using the center punch in the chuck as a guide as Frosty suggested. I then thought it might help to center drill the hole, so I used a #1 center drill on it. I then drilled the pilot hole for the tap. After all this I missed the casting seam by 1/32nd, same as last night. That was my last 3/4 x 1/2 tee, so I'm settling on last night's tee until I can get some more tees.

I promised concerned 3rd parties that I'd stop making trips to the hardware store with the new covid strains around, so I'll have to order more tees online and wait for them to ship to try and hit that elusive 1/64th tolerance. Just saying "elusive 1/64th" I feel like I'm the laughing stock of fabricators everywhere. :D That's alright, I boost other peoples' confidence. I'm useful!

I think I could have a shot at hitting 1/64th with a spotting drill (don't currently own any but not too expensive). I'm thinking center punch a la Frosty method, re-align a la Frosty method, spot drill, pilot drill, tap. If a spotting drill can't convince this drill press to behave, then I think I'll be stuck at 1/32.

In more exciting news! The bricks arrived today, and I've started drawing my plans for the interior and nozzle. Here's a sketch of a cutaway view at the dead center, where the inner diameter is widest (2-3/8"). To clarify, the inner diameter will taper down to 2-1/8" at the ends of the 9" length, per Tristan's instructions.


I know some of the handwriting isn't easy to read so here's some of the major points. The end of the burner tube will rest flush with the wall of the firebrick. (That means this forge will absolutely need an external mount for the burner). The nozzle tapers from 27/32" (the OD of the mixer tube) to 1" over 1" length. That gives a rise/run of 1/12.8. I settled for that because the dimensions are easy to hit. Make the smallest ID just big enough for the tube to fit inside, and the largest ID 1" flat. I'm going to cut a wooden trapezoid to use as a go-no-go gauge.

And for those who aren't familiar, this is the forge I'm attempting to recreate.

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Twigg:  I'm not a machinist but I have found that a drill bit wanders less if only the minimum amount is sticking out of the bit.  If the material you are drilling is 1/4" thick, only have a bit more than 1/4" sticking our of the chuck.  Also, a bit will wander off if the initial surface it is starting in is not flat.  The head of the bit will bite differentially and will deflect "downhill."  So, if where you are starting your hole is irregular or sloped, file or grind a small flat area to start the hole.  That's all I've got except to suggest that if it is beyond your available equipment and skill it might be worthwhile to pay to have it done at a machine shop.

I hear you about being restricted from going to the hardware store because of covid.  I've had to kludge a lot of things recently with whatever I already have on hand to keep domestic peace.

BTW, the Rocky Mountain Smiths 2021 summer conference has been cancelled because it is unclear if it will be safe by August.

"By hammer and hand all arts do stand."

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Thanks George! Yeah, I think the problem may be the casting seam itself deflecting the center punch. There's no way the center drill should have wandered out of the punch mark on its own. Maybe I was missing my punch mark but I couldn't tell because the punch mark was harder to see than the 25/64" pilot hole. If that's the case, then like you say, filing a flat is my only way to higher precision. I figure that if I'm off by 1/32nd (31 thou), that's about one jet orifice diameter worth of offset. Ideally I'd like to have my tolerances less than one orifice diameter, but I feel like I'll still get a non-junk burner with 1/32nd offset (experts, correct me if I'm wrong). At this point it's more a matter of principle than a necessity. On the flip side, I feel like once I figure this out, it'll help me in future endeavors (even if all it does is teach me the limits of this equipment).

For anyone who does have high end machining tools, a more mechanically inclined family member suggested to me that a 4 flute center cutting square end mill will wander less than a drill bit on a curved surface. I'm not convinced it would help me because of the slop in my drill's chuck.

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I've found that coating the porous, granular flame-facing surface of Insulating Fire Bricks (IFBs) definitely increases their life-span.

They are going to crack sooner or later anyway. That is the nature of IFBs. But a protective coating (in my case a Zircopax/Colloidal-Silica wash) seemed to fill in the tiny openings in the porous surface and made it weather the direct flame better.  The surface seemed less crumbly after repeated high-heat direct-flame contact.

I don't use uncoated IFBs in direct-flame contact any more, for this reason.

Just my £0.02 worth, Hope it helps.


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11 hours ago, twigg said:

I took the flange off the drill table,

(SIGH) The floor flange stays clamped to the drill press table until you're finished making and testing the burner! There are ways to re-clamp it after moving but its a major PITA even if you've been doing it for years. Just buy another floor flange if you need one elsewhere before the burner is finished. Only unscrew the T, the close nipple isn't as strong nor stable so using it as a base to center punch against isn't so good.

That floor flange is your witness mark and moving it makes it NADA. It's like virginity, there is NO REDO, once gone it's gone forever. PERIOD.

And YES your center punch mark needs to be strong enough the drill bit doesn't wander off. Try filing the flash off AFTER punching it, just don't file through the punch mark, re-punch it if you have to. How about buying a "Center drill bit?" The one in the tail stock drill chuck in the pic in the Illustrated instructions is a "center bit," They're short and do NOT wander. If you're using a lathe you don't need to measure, mark or punch a center bit will hold position flash or uneven surface.

Flash is the proper term for the excess metal residue from between mold halves or forge dies. That's just a FYI, not criticism.

Frosty The Lucky.

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I'm sorry, Frosty. I don't know why I didn't process that I was supposed to remove the tee and leave the flange. Thanks for bearing with me! If we ever meet, I owe you several beers. I did a practice run on a 1/2 x 1/2 tee, and it's dead nuts on. I measure 0.008" offset from the flash. I'm measuring this by looking at the distance from the corners of the hex on the brass fitting from the flash with calipers and taking the difference, so I'm sure there's significant measurement error, but to me this is just a number for quality control.

Frosty, I think a center drill would be counter productive. I did a dry run with a #2 center drill and found that I don't have enough feed to change from a center punch to a center drill without moving the table up, and then down again for the pilot drill. Yesterday I was only able to center punch drill because I removed the flange.

Note to self: read Frosty's messages 3 times. Sleep on it. Read them 3 times more.

Piece of advice to those following the thread: Clamp the ever-living muffins out of the floor flange (without messing up your drill table). Don't use locking clamps like I did, use c clamps like shown in Frosty's instructions. Build a jig if you have to. Same goes for tightening the nipple to the flange. When you drill your pilot hole, the drill will tighten the the tee into the nipple. When you go to remove the tee to center punch it, if you didn't use enough torque, the nipple will come out with the tee. You could probably restore alignment from there, but it's an unnecessary hassle. Just torque the nipple to the flange with a pipe wrench and vise. I only have one of those flex head pipe wrenches (I forget the name, start's with a "b"), and I didn't use my weight just pulling strength, and that wasn't really enough. The nipple started backing out on me.

Pnut and tinkertim, I think it got lost back on the first page of this thread, but I was going to follow a bunch of people's advice to use a plistex coating as flame protection and IR emitter. I didn't include the thickness of the coating in the drawing because on the "consolidated notes" thread, it says "thick is counterproductive [for matrikote]" and to just paint it on.

The only thing I didn't address is Frosty's concern that plistex does not bond well to smooth surfaces. I was hoping that the cut and scraped out interior surface would be rough enough that the plistix would have some purchase, but I honestly don't know.

Tinkertim, so my coating needs to be thick enough to fill the open cells of the brick. Thanks for the info!

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17 hours ago, twigg said:

I know some of the handwriting isn't easy to read so here's some of the major points. The end of the burner tube will rest flush with the wall of the firebrick. (That means this forge will absolutely need an external mount for the burner). The nozzle tapers from 27/32" (the OD of the mixer tube) to 1" over 1" length. That gives a rise/run of 1/12.8. I settled for that because the dimensions are easy to hit. Make the smallest ID just big enough for the tube to fit inside, and the largest ID 1" flat. I'm going to cut a wooden trapezoid to use as a go-no-go gauge.

This arrangement will help the burner to last well. But, the firebrick won't, unless you coat it with something to keep the flame from attacking it! Aside from this, your design looks very sensible. I look forward to seeing it in action.

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I hear you Mikey. I'm going with plistix, per your suggestion earlier in the thread. :)

I'm still figuring out how to hole saw my way through the 9" length of the bricks without wrecking them, so I'm holding off on shaping the interior. The 3/4 x 1/2 tees are expected to arrive Tuesday I bought a lot of 10 thinking I had more experimentation to do. :wacko: So tonight I did the basic frame.


Dealing with the bedrail was uneventful. I got lucky and the bed rail was all mild steel (file bit right into it), so I was able to cut it with a hacksaw (still can't throw sparks). For those following the thread, bed frame often is carbon steel, or a mixed bag. A quick google search will show many a frustrated forum post about busted drill bits and saw blades wasted.
Naturally, the 1/4-20 threaded rod I thought I had lying around turned out to be 5/16-24, so I had to online order hex nuts in that size. They too should be here Tuesday.

Still thinking how I want to mount the burner.

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Good Morning,

Those bricks are very soft, you could use a sharp knife, a sharp spoon, a fast spinning slow moving Forstner Bit or a hand saw. Think simple, what do you have? It is not a complicated decision. Use what you have available, BE BRAVE Make a decision. You need to get Forging!!

You may want to also run the threaded rod, 90 degrees to the way they are in the picture. Yes, the bricks will break up with the heat and then cooling, over thyme. Everything will expand and contract.

Enjoy the Journey, there is no destination!

Good Luck, Neil

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3 hours ago, swedefiddle said:

You may want to also run the threaded rod, 90 degrees to the way they are in the picture. Yes, the bricks will break up with the heat and then cooling, over thyme.

Horizontal all thread would definitely spice it up! (Sorry, I just couldn't help myself) I'll get on it.

I hear you about getting forging, but I'm still waiting on the plistix to arrive, so I figure I might as well have some fun. Honestly, I'm enjoying the journey right now even if the hours I'm putting in are a little silly. You're right though, I have 4 bricks total and I can experiment. I like the spoon idea. Hope my landlord doesn't think I've lost it if he sees me sharpening a spoon... :wacko:

Ah, I already cut off the threads on the mixing tube, Mikey. That might've been a little premature on my part. I do still have extra shower rod flanges like I used on my rectangular forge. I think I can pop rivet one of those onto a piece of sheet metal and bolt that onto the angle iron. (I do have access to a mig welder, but all my spare sheet and the shower rod flange are stainless) I'll let you know what I come up with.

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Alrighty, shaped the interior tonight and added horizontal threaded rod to the frame. Doing the interior was a lot easier than I thought it would be. I used a 2" hole saw (all I had on hand). I took "bites" with the hole saw, then switched to a 1/2" bit and drill holes into the remaining cylinder to weaken it, then used a screwdriver to break it apart. I had to chase the hole from the other end of the bricks to get it all the way through, so make sure to center the hole saw pilot bit.

To make the burner flare, I started with a 3/4" drill bit, and filed it with a rat-tail file until I could fit the burner tube inside. Then I got myself a 3/4" socket with a 1" OD for a gauge. I filed a flare into the hole until I could fit the OD of the socket in the end of the flare (see pictures).

Then I scraped out a taper to make the center of the forge have 1/4" wider walls (added a 1/2" to the ID), per Tristan's advice. I did this with dull woodworking chisels.


I didn't scoop much out of the burner side so I wouldn't mess up the nozzle. Now the center has an ID of 2-1/2" and the openings have 2" IDs. The taper now runs a little flat because I didn't scoop out that side. I need to do a little more tweaking there.

Here's the mock-up assembly:


(there's just enough length on the horizontal rods to thread a nut on either side, I almost messed that up)

And lastly I figured out a way to mount the burner with what I have lying around. I have some 18ga stainless sheet I can cut into pieces the size of the forge's outer dimensions, and pop rivet them to the angle iron. I have a flange I can pip rivet to the sheet. I just need to wait until I can throw sparks again. Unless anyone knows a way to cut 18ga SS without a grinder or access to a brake?


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