propane forge

Khukuri Monster

Khukuri Monster

Joined
Aug 4, 2004
Messages
373
I just got finished building a couple of propane forges, one for myself and one for Jebediah_Smith. I already had a propane forge, but I found that it was much too large for working on knives, and it would waste heat. The larger forge would also take a long time to heat up.

Here's a picture of the finished forge. It was kind of dark when I took the pictures so they are pretty fuzzy.

http://www-personal.umich.edu/~robgaunt/pics/newforge/forge.JPG

This one is 14" long and 8" diameter. The inside is lined with 2" of ceramic fiber blanket for insulation, and has a floor made out of soft fire brick. I coated everything with a heat-reflective refractory. It has two venturi burners. On this forge, I used smaller burners, so it runs at a higher pressure but lower volume of propane. This seems to give increased suction over the larger burners, and more control.

I'm quite happy with this forge, it heats up very fast because of the smaller diameter. Here's a couple of pictures of the inside about 30 seconds after starting it up.

http://www-personal.umich.edu/~robgaunt/pics/newforge/forgeinside.JPG
http://www-personal.umich.edu/~robgaunt/pics/newforge/forgeinside2.JPG

Here's a picture of the plumbing setup.

http://www-personal.umich.edu/~robgaunt/pics/newforge/forgeplumbing.JPG

I have a bypass with a needle valve set up. The needle valve gives me fine control. I measured the forge temperature with a thermocouple, and I can control it within a couple of degrees. It also allows me to let the forge "idle" when I go work on the anvil. When you turn off the main valve the needle valve lets a little gas through to keep the burners going.

The total price for the forge and plumbing was around $100, the regulator, hose, and associated fittings cost another $50 or so. A lot of the cost was in the plumbing setup. Even though each part is pretty cheap, you need quite a few of them.
 
I forgot to mention, you can easily run one of these forges off of a regular barbecue grill size (25 lb) propane tank.
 
Hey KM, I just got back from a little night time forging session. I made that piece of railing support into a nice little pair of tongs. No more vice grips for me. And I cleaned up the double edged persian dagger a bit. The forge runs like a dream.
 
That looks great!

Gotta love the fire! :eek:


Be sure to post pics of the first blade you make from it.
 
Man I wish I had one of those and could set down at the anvil.
I have a Big Assed Bowie in my head wanting out, may have to resort to stock removal using O-1 tool steel.
It's damned hard to find 5160 in a 5/16"-3/8" thickness 3" wide and 18"-24" long, but I can get it at our local Wholesale Tool Co. in O-1 tool steel.:D
Of course I could maybe try a truck salvage for a fat piece of discarded truck spring but I'd rather have known material and O-1 is just a pretty damned good steel at 60 Rc hardness. That's what I made my fancy knife with back in '74 and I chopped down a 4" sapling with no chipping.:D :cool: :D
 
Yvsa, you might want to check www.flat-stock.com for O-1 too. They seem to have the best prices, and you can get whatever dimensions you might want in 18" or 36" length. Shipping prices are usually reasonable.

I'm not sure where you can get a small chunk of new 5160. Usually you have to buy a huge 20 foot bar.
 
I picked up some John Deere Load Control Shaft from Dan Gray a while back. It was a 1.25" diameter round bar. I forged it out yesterday to 3/8" thick flat bar that was 2" wide - plenty for making a khukuri or large bowie. Didn't cost that much either....$8-10, IIRC.

You are welcome at my forge any day of the week, Yvsa. Come on down and we'll flatten out a bar - I have several shafts left, and we can also forge the blade to shape.
 
Can I have a parts list ? it looks like exactly what I need.

Think it will bake potatoes too? probably do a mean steak, in like
10 seconds.....
 
There's a couple of webpages you can check for general information on propane forges:

http://www.frontiernet.net/~gnreil/design1.shtml
This page is not very well organized, and some information is outdated or redundant. But the burner turning information is helpful, along with some design considerations.

http://www.geocities.com/zoellerforge/sidearm.html
This page has details on constructing the burners that I used. This burner design seems to be the most effective of all those that are made from off-the-shelf plumbing parts. It's a venturi, so you don't need a blower, and you can build the burners for about $20 each. Higher performance burners are possible, but you will need to buy them (check www.hybridburners.com - they are expensive), or have a metal lathe and machining experience.

I used the "mini" side-arm burner for the new forge and I think it works better than the larger burner. High pressure and low volume seems to be the way to go for venturi burners. I had the larger burners in my oversized forge and they didn't work as well.

The stainless steel burner flares that Larry Zoeller sells are most definitely worth it.

http://www.geocities.com/zoellerforge/forge.html
More forge construction information.

http://refractory.elliscustomknifeworks.com/
Check their forge gallery page for more inspiration. This place also sells supplies but I suggest checking locally for a refractory supply place or a place which sells furnaces. You may be able to get a lot of the stuff for free.

So, here's the parts list for my forge. You can get the parts list for the burners from the above sites.

8" diameter x 14" long shell (I would increase the diameter to 10" and use 3" of insulation in the future. 2" still lets a little heat out.)

One soft firebrick, split in half lengthwise, for the floor. You will also need a couple more soft firebrick to close up the entrances. Don't use hard firebrick! It absorbs the heat instead of insulating. If you do have to use hard firebrick, use the kind for pottery kilns, not the commonly available kind for fireplaces.

Enough ceramic fiber blanket to go inside the forge shell. You probably only need a couple of square feet - but calculate first. I actually got mine for free from a refractory supply place. They built large industrial forges and had some "scraps" that were about 2' x 3', plenty large enough. I also got some free scraps of Insboard, probably several square feet. Normally that stuff is $24 per square foot. It works great for blocking off entrances instead of firebrick.

Some sort of clay refractory to go over the blanket. I used some stuff called Satanite. This prevents the ceramic fibers from blowing loose, floating through the air, and into your lungs.

You can also use a special refractory topcoat like "ITC-100". People claim that this helps reflect heat back into the forge. However, I talked to a ceramics engineer who builds furnaces for a living, and it was his opinion that ITC-100 was overpriced and just hype - any sort of coating will do.

That's it for the forge body.

You also need a collection of 1/4" pipe fittings - tees, valves, elbows, and nipples. You can get an idea of the parts by looking at my plumbing picture. I suggest getting the parts at a plumbing supply house instead of Home Depot. Usually these fittings are more heavy-duty, especially the valves. You can get a needle valve at a heating/cooling supply store.

The regulator and hose are available from Zoeller Forge or your local propane dealer. They also have fittings that will connect the regulator to a BBQ grill tank.
 
Daniel Koster said:
You are welcome at my forge any day of the week, Yvsa. Come on down and we'll flatten out a bar - I have several shafts left, and we can also forge the blade to shape.
Click to expand...
Dan thanks a million and I may take you up on it some day if I'm able again but we'll have to wait and see.
I'll have to get a piece of steel though as I'm expectin my Bowie to be between 2-1/2"- 3" wide in the beam.:eek: :rolleyes: :D ;) I haven't even drawn it out yet as I'm trying to decide which style I want to make. If I was younger I'd make all three of the styles I consider to be Bowies and be done with it.:D :cool: :D
 
I was going to build something , it was either a still or a forge.
I think the forge will keep me out of trouble, Thanks for all the info.
I am one of those sick puppies that will have to scrounge the part , that makes it more fun, you have got me a lot of information and I do have access to a mill , this is going to be fun.

so you have never tried to cook anything with a forge? no? I find that hard to believe, I'm sure you would work up an appetite pounding iron.....
 
LOL....it would work, but it would taste like burnt carbon....:barf:

At least, that's what I come home smelling like, and I keep my distance.....:eek: :footinmou



On the ShopTalk forum, Indian George has a set of plans for making a nice burner/blower setup. The nice thing about having a blower (vs. venturi) is that you can get the temps up higher, faster. You can also cool it quicker. Best part, though, is being able to run very low pressure. Look on knivesby.com for the link.
 
I've never cooked on the forge, but I have a good trick for reheating your coffee. I used to get my fire poker or a scrap piece of stock red hot in the forge and then plunge it into my cup. Voila, hot coffee again (and an iron supplement to boot)!

Yvsa, for your stock I would check and see if there is a spring shop around. I used to be able to buy drops and shorts from Betts springs for either their cost or the price they sold it to the scrap yard. :)
 
stevomiller said:
Yvsa, for your stock I would check and see if there is a spring shop around. I used to be able to buy drops and shorts from Betts springs for either their cost or the price they sold it to the scrap yard. :)
Click to expand...
Thanks Steve.
I did go to our local spring shop a few years back when I got the knife making urge again and I bought several pices of spring steel.
Some of it is marked, like the 1084, but some of it isn't, but spring steel is pretty forgiving on heat treat thankfully.
They couldn't guarantee me any 1095 or 5160 and I was lucky to get the 1084 I felt like.
 
Absolutely great stuff, Khukuri Monster.

Going to bookmark this thread for future reference.


Ad Astra
 
Daniel Koster said:
On the ShopTalk forum, Indian George has a set of plans for making a nice burner/blower setup. The nice thing about having a blower (vs. venturi) is that you can get the temps up higher, faster. You can also cool it quicker. Best part, though, is being able to run very low pressure. Look on knivesby.com for the link.
Click to expand...

I think that's debatable. With a good venturi and a burner flare, you can run these burners down to 1 psi or below, although they work better at higher pressure. There was a discussion a while back on Don Fogg's forum where people debated the merits of a venturi vs. blown burner. The forced air burners also put out a larger volume of propane, so the pressure readings alone are misleading.

http://forums.dfoggknives.com/index.php?showtopic=2961&hl=venturi
 
Yes, it's debatable....comes down to what matters most to you.

The forced air burners also put out a larger volume of propane
Click to expand...
Not necessarily. The propane has its own needle valve seperate from blower's gate valve. They are controlled independently. It's really quite a simple setup and very inexpensive. I can take the temp down to 1200 and can hold it very easily (digital pryometer).

I've used all three basic types, and prefer the blower for the safety and ability to control it. (Not trying to put yours down).
 
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