bending the waist on a hot pipe

Matt Clara

Matt Clara

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My 3 inch pipe is too big to bend tight waists, such as those required by my form. I have a line on a 1 inch cartridge heater that will fit exactly inside a 1 inch pipe, and I'm thinking about going that route to create a simple solution. My only concern is, 1 inch might be too small, leading to cracks and breaks. For the cartridge to work, though, it needs to be in contact with the sides of the pipe, and 1 inch is the biggest I can find.

Any thoughts?
 
Long before electricity was available Spanish builders were bending sides using a section of pipe heated by placing a small butane/propane torch placed inside the pipe. It goes without saying that you should take all precautions when using an open flame in a workshop, especially by ensuring that any flammable solvents are stored safely, there are no open jars of french polish sitting around, etc.
 
I would say just start the bend with the 3 inch pipe and then move to the 1 inch once you've gotten as far as you can with the 3 inch.
 
My local muffler shop gave me a couple scrap pieces of aluminized exhaust pipe about 9 or 10 inches long. They come in a couple of sizes. Mine are 2 1/2 inches and 2 7/8 inches. Or maybe, you can get or use smaller regular exhaust pipe. Muffler shops make a lot of scrap.

John
 
This is the setup I use. It is simple, cheap, and works fine. The pipe is a piece of 2" muffler pipe I got free as a cutoff from the local muffler shop. It is capped off with the bottom of a tomato paste can and a hole is drilled on the bottom side of the pipe to let hot air escape. The torch provides plenty of heat and is easy to regulate. The 2" pipe was perfect for the saprano I just made.
 

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I tried a 1" pipe and found it was too small for bending. That's 1" NPT pipe from the hardware store.....I don't know what the actual outside diameter is. I just got creases and cracks with my practice pieces.
1 1/4" is what I use for Uke bending. My Wagner heat gun nozzel fits inside a 1 1/4" pipe perfectly....no need to devise a holder for it. Its a small pipe but for most woods I can bend the bouts on it ok.
 
ksquine said:
I tried a 1" pipe and found it was too small for bending. That's 1" NPT pipe from the hardware store.....I don't know what the actual outside diameter is. I just got creases and cracks with my practice pieces.
1 1/4" is what I use for Uke bending. My Wagner heat gun nozzel fits inside a 1 1/4" pipe perfectly....no need to devise a holder for it. Its a small pipe but for most woods I can bend the bouts on it ok.
Click to expand...
Do you have any idea what the surface temp of the pipe is using a heat gun? I'm going to experiment today with a heating element from a water heater, 240 volt, 4300 watts, screwed into a length of 1 1/2 inch pipe, hoping I don't pop the breaker, burn out the element or burn the house down. I have no idea what those elements are rated for, temp wise, or if it will even work. Had it laying around in the garage .... which is perhaps where I should have left it...
 
I bend on a Stewart McDonald bender I got in the 80's. It heats to around 550 and give a really good bend it has a 1 inch end on the air foil shape. I use the 1 inch for the tight curls on fiddles. I start with the bigest curve and work my way down to the 1 inch diameter. Haven't had a problem yet but you must go very slow.
 
Muffler pipes... brilliant! I still have those stock Harley pipes I took off my bike someplace :)
 
I've used this one I made for violins for years. Before this one I had a brass pipe for guitars. the brass seamed to transfer the heat better with less scortching...
bending-iron.JPG
 
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Hi Nu Uke

I don't know how hot it gets.....but its much more than enough for bending. I run it on High for 5min to heat up the pipe then run it on Low. After 10min or so I have to turn it off or the pipe gets too hot. My pipe is open at both ends and the gun blows straight through it.
I thought the heatgun noise would be too irritating to enjoy my wood bending sessions. The new gun I got really isn't that bad. I don't even have to turn up the radio.

4300Watts sounds like way too much power!!! Even if you ran it at 120V. I use a 550W charcoal starter for heat in my 3" pipe and I have to use a router speed control to turn it down.
 
Hi ksquine,
Yeah, I'm having second thoughts on the water heater element. I didn't hook it up yesterday, couldn't find a switch rated for 220 volts in my stash. You're probably right. 4300 watts seemed a bit much to me too! Probably start myself on fire. I don't know anything about those elements either. Might be meant to be used totally submerged. For now, I'm falling back in my second design. 2 1/2 inch iron pipe nipple mounted to a flange. But did get a brainstorm thanks to Axmaster. I have a six inch length of heavy wall, 7/16ths, naval bronze tube, which fits perfectly inside the iron pipe. I'll use it as a slightly narrower bender protruding out of the end of the iron pipe, held in with set screw. I may try my heat gun. Mine sure doesn't look as heavy duty as the one shown in Axmaster's pic. I'm building the jig to use a propane torch with flame spreader to disperse the heat within the iron pipe, hoping the bronze pipe acts as a heat sink and gets hot enough to use. Should work. Thanks Ksquine.
Scott
 
Ultimately, the idea of using a non integrated heating source such as a propane torch makes me nervous--I tend to walk away from things and then forget about them. As some of you indicate 1 inch isn't too small, provided one has enough heat and goes slowly, so I'm going with the 1 inch pipe, a 600 watt 1 inch heater cartridge and a 600 watt dimmer switch. I'll let you know how that works out. I estimate total cost around $40, so that means I'll probably spend twice that on it ;)

I'm thinking of rigging up a stand for the pipe out of wood. Anyone know of some simple insulation to put in between the pipe and the wood stand? Even if I do end up with metal instead of wood, I'd like some insulation to keep the heat in the pipe, and out of the stand.
 
I'm thinking of rigging up a stand for the pipe out of wood. Anyone know of some simple insulation to put in between the pipe and the wood stand? Even if I do end up with metal instead of wood, I'd like some insulation to keep the heat in the pipe, and out of the stand.[/QUOTE]

Matt,
I just finished this fixture today. Might not be simple ... to find.. but I sandwiched some pieces of heavy asbestos woven fabric between the iron flange and plywood support. Cut it off the bottom of an old welding apron I had. Lemme know if you need a few pieces. I don't weld.
I'm with you, propane scares me a bit. But I built this anyway.
Scott
 

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Nu Uke said:
Matt,
I just finished this fixture today. Might not be simple ... to find.. but I sandwiched some pieces of heavy asbestos woven fabric between the iron flange and plywood support. Cut it off the bottom of an old welding apron I had. Lemme know if you need a few pieces. I don't weld.
I'm with you, propane scares me a bit. But I built this anyway.
Scott
Click to expand...

That looks fantastic. You should see the (surprisingly sturdy) piece of crap I schlepped together for my 1" pipe.
Sent you a PM.
 
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