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Thread: bending pipe

  1. #1

    Default bending pipe

    Is electrical conduit heavy enough to make a side bending pipe using a propane burner?

  2. #2
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    Default Re: bending pipe

    I've been building mandolins over 20 years, and in that time, all I've ever used is electrical conduit.. I have two different sizes, one is 3/4 inch, the other is 1 1/2 inch.. The smaller is used 4 times more then the bigger.. I welded 1/4 inch strapping to hold in my bench vise and centered a propane torch into the pipe.. placed a metal screen in the end as a plug to help keep the heat in better(and after burning holes in a few shirts)... it heats up quickly, but can scorch if it gets too hot and if the wood looses moisture.. the surface of conduit is a lot smoother then say plumbing pipe... using stainless strapping when bending helps a lot too...
    kterry

  3. #3

    Default Re: bending pipe

    I have had pretty good luck using a hot plate and a copper pipe. I have a couple of different sizes of copper pipe. The copper conducts heat better than the conduit and is readily available. I went to the hot plate to get away from open flames in my shop. It is not a very elaborate set up but has worked for A-style mandolins. The hot plate is a Wal Mart special or something like that. I use some straps and clamps to hold it in place. I have not tried any scrolls yet.

  4. #4
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    Default Re: bending pipe

    I’m pretty sure conduit is galvanized. Which give off a very toxic gas when heated. Make sure you have a really well vented area to burn it off.

    Adam

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    Default Re: bending pipe

    Quote Originally Posted by addamr View Post
    I’m pretty sure conduit is galvanized. Which give off a very toxic gas when heated. Make sure you have a really well vented area to burn it off.

    Adam
    If it is galvanized, Yes, definitely burn off the galvanized coating before using the conduit.
    THE WORLD IS A BETTER PLACE JUST FOR YOUR SMILE!

  7. #6

    Default Re: bending pipe

    Thanks to all who replied to this. This forum is awesome!

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    Registered User Bob Visentin's Avatar
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    Default

    ok

  9. #8

    Default Re: bending pipe

    yup 20 years of building and i only use a 2inch cast iron plumbing pipe with a propane torch I also use a piece of aluminum trim coil as a strap works pretty well

  10. #9
    Kelley Mandolins Skip Kelley's Avatar
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    Default Re: bending pipe

    I use a bending iron that I made. I found the information online somewhere, years ago. It's an aluminum pipe with a dry water heater element inside. It works fine.

  11. #10
    Adrian Minarovic
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    Default Re: bending pipe

    I use such one as well. 2" dia plumbing pipe with electric heater stick inside, One end welded and whole filled with fine washed sand. Other end closed with lid made of piece of sheet metal.
    I just made an extension for smaller diameter out of piece of SS tube with one end welded and filled with slurry of fireproof filler mixed with fine sand. It is bolted to the end of the heated tube like the SM bending iron extension.
    Adrian

  12. #11
    Registered User Mike Conner's Avatar
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    Default Re: bending pipe

    My bender is also 2" heavy wall galvanized pipe. The heat source is a charcoal starter compressed to fit tight inside the pipe and controlled with a 600W light dimmer. I monitor the temperature with a long temperature probe sold for using with deep fryers (eg. turkey fryers). Pretty inexpensive, has lasted a long time. The heavy pipe holds the heat really well. Haven't needed a smaller diameter pipe so far - I can heat the tighter bends from the outside of the bend by rocking on the pipe, plus that's the surface that needs to "stretch" during bending.

    Click image for larger version. 

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  13. #12
    Registered User John Bertotti's Avatar
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    Default Re: bending pipe

    What are the preferred ways to heat? I see some use propane while others dig up heating elements. Somewhere I have some silicone heating pads. They got boxed in a move and I still haven’t come across them. I like the idea but wonder how well they will work.
    My avatar is of my OldWave Oval A

    Creativity is just doing something wierd and finding out others like it.

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    Ursus Mandolinus Fretbear's Avatar
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  15. #14
    Registered User Mike Conner's Avatar
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    Default Re: bending pipe

    In my case, I had read of others receiving scorched shirts or worse from propane or other combustion sources. I also was concerned that my smaller original shop had plenty of combustible dust and other materials. The opportunity for a set control of temperature using the electric source was preferred for me.

  16. #15

    Default Re: bending pipe

    Are all these heating elements (charcoal lighter, water heater) easily bendable to fit inside a 2" pipe?

  17. #16
    Registered User Mike Conner's Avatar
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    Default Re: bending pipe

    Quote Originally Posted by Dan of SC View Post
    Are all these heating elements (charcoal lighter, water heater) easily bendable to fit inside a 2" pipe?
    I had no problem compressing the charcoal starter down. I have a heavy iron bench vise that worked great. I was concerned about losing the electrical integrity due to the compression but no problem, and I am still using the original heater with no problems at all. You have to cut up the handle end to access the wiring and connect to the dimmer control. Way easier than I expected, and all together rather inexpensive.

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    Registered User bpatrick's Avatar
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    Default Re: bending pipe

    For years, I used a heavy walled 2" steel pipe with a piece of metal screwed across the non-torch end. This was heated by a propane torch. This set up worked pretty well, but I was always a bit leery of working around an open flame. Also, the pipe was somewhat unevenly heated. The propane torch created a hot spot closest to the flame and was cooler away from it. Somewhat of a "too hot" area and "not quite hot enough area". I suppose this might be a good trait for some builders, but I'd rather work with a more consistent heated area.

    I like to build a lot of my tools and jigs, but 4-5 years ago, I bought a Stew Mac electric heater complete with the smaller extension. It's a little slow to heat up, but provides even heat and is safer and easier to deal with.
    Bryan Patrick

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    Registered User John Bertotti's Avatar
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    Default Re: bending pipe

    I wonder how well an engine block heater would work, small enough you wouldn't have to crush it. But you would need to run it at 12 volts if it's like my tractor or a car one I think might be 120 volt.
    My avatar is of my OldWave Oval A

    Creativity is just doing something wierd and finding out others like it.

  20. #19
    Registered User Mike Conner's Avatar
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    Default Re: bending pipe

    My bender in action:
    https://youtu.be/NRdh_jVhQUY

    I am very non-photogenic. Recommend caution if you choose to expose your eyes to this. ;-)

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  22. #20
    Adrian Minarovic
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    Default Re: bending pipe

    Quote Originally Posted by Mike Conner View Post
    Haven't needed a smaller diameter pipe so far - I can heat the tighter bends from the outside of the bend by rocking on the pipe, plus that's the surface that needs to "stretch" during bending.
    Actually you don't want to stretch the outside too much, especially on flamed maple the stretching is reason for all the splits during bending. Generally wood bending is done by removing as much tension from outside as possible (by use of steel belts secured to both ends of wood) and rely completely on compression of the wood on the inside of the bend. Thin ribs can be bent without the fixed bending strap or even without simple strap but you need to go slow and not allow the outside to break.
    Adrian

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  24. #21
    Adrian Minarovic
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    Default Re: bending pipe

    Quote Originally Posted by John Bertotti View Post
    I wonder how well an engine block heater would work, small enough you wouldn't have to crush it. But you would need to run it at 12 volts if it's like my tractor or a car one I think might be 120 volt.
    There are many simple heating elements available in form of thin stick with two wires at one end. Some are even bendable. Just choose the power you need. You can fill the pipe with sand or fireclay, that will keep the heat distribution more even.
    Adrian

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  26. #22
    Registered User John Bertotti's Avatar
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    Default Re: bending pipe

    I’m searching for my box of silicone heating pads first. I think they get plenty hot enough. Sadly the box was misplaced in a shed or storage years ago when we moved.
    My avatar is of my OldWave Oval A

    Creativity is just doing something wierd and finding out others like it.

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    Default Re: bending pipe

    I have bent guitar sides on a mold using silicone heating pads, it works fine. The sides bent by hand retained their shape better than those bent on a mold, but both worked.
    THE WORLD IS A BETTER PLACE JUST FOR YOUR SMILE!

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  29. #24
    Registered User talladam's Avatar
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    Default Re: bending pipe

    I have already posted this in my build thread, but here is my mad scientist bender:

    Click image for larger version. 

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    It is made with electrical conduit but it is 'rigid aluminum conduit' rather than EMT which is the galvanized kind (in Canada anyway). Unless you know an electrician you'd have to purchase a 10' piece which would probably be more expensive than you'd like. I've heard of people who get stains from aluminum but I haven't yet. I screwed together a small piece and a large piece for different radii.
    Eastman MD-315

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