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| How to avoid cocked sides when bending on a bending iron? http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=31984 |
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| Author: | UkeforJC [ Tue Apr 26, 2011 12:29 pm ] |
| Post subject: | How to avoid cocked sides when bending on a bending iron? |
Dear all, I have come to ask for some advice again. I do my best to describe the problem I had.. I was bending some walnut sides on a bending iron. No matter what I tried, the sides always become cocked at an angle. I read an article from Stew Mac saying: "Important tips....Keep your work squared up! Keep the straight (top) edge of the sides aligned with the tip of the bending iron or with the bender’s mounting block. Don’t let your bending work become cocked at an angle. " http://www.stewmac.com/freeinfo/I-0689.html I have tried my best to do that, but the bended work is still cocked. Can any one give me some advice on how to improve this? THANK YOU !! Jc |
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| Author: | pvg [ Tue Apr 26, 2011 1:45 pm ] |
| Post subject: | Re: How to avoid cocked sides when bending on a bending iron? |
Don't know what type of bending iron you're using; but with my rather primitive set up- a hunk of pipe and a propane torch- I ran into the problem of unequal heating of the pipe. The closed end gets quite a bit hotter than the open end. The "open" end is where the flame goes in, and the "closed" end is not shut up tight-it has vents to allow the heat to pass through the pipe. Anyway, getting even heat distribution is a bit of a problem. pvg |
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| Author: | UkeforJC [ Tue Apr 26, 2011 5:04 pm ] |
| Post subject: | Re: How to avoid cocked sides when bending on a bending iron? |
I just use a very simple bending iron that I made. Not too sure whether the pipes are heated unequally. |
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| Author: | John Arnold [ Tue Apr 26, 2011 9:14 pm ] |
| Post subject: | Re: How to avoid cocked sides when bending on a bending iron? |
How is your bending pipe oriented? I have not had that trouble with a horizontal pipe. Quote: getting even heat distribution is a bit of a problem. My propane torched pipe is aluminum, which seems to heat pretty evenly, at least on the baffled end where I do the bending. It measures 3 1/2" in diameter by 16" long, with a 3/16" wall. |
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| Author: | Hupaand [ Tue Apr 26, 2011 9:22 pm ] |
| Post subject: | Re: How to avoid cocked sides when bending on a bending iron? |
Have you tried orienting your 'T' the other way, so the heat goes in one side of the t, straight through, and out the other? I wedge a ball of aluminum foil in the end. I still get some canted sides, sometimes, but I think the heat is pretty consistent. |
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| Author: | David Newton [ Tue Apr 26, 2011 9:43 pm ] |
| Post subject: | Re: How to avoid cocked sides when bending on a bending iron? |
I mount my electrically heated iron in the vise at the left end of my workbench, and have my sides mould on the bench top for constant reference as I'm bending. I bend the waist first and make sure it is square in the mould. |
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| Author: | WaddyThomson [ Tue Apr 26, 2011 11:02 pm ] |
| Post subject: | Re: How to avoid cocked sides when bending on a bending iron? |
A lot of that occurs from uneven pressure on the top and bottom edges of the side as you bend. Always check your side to a template or a mold or something that you can work against and use a machinists square to see if it's square as you bend. Check often and carefully. You can correct off square bends by working obliquely to the pipe and putting more pressure on the other edge to square it up. Sometimes you have to relieve the bend a bit by bending back toward straight, then re-bending that section. Happens all the time, to me. |
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| Author: | JasonMoe [ Wed Apr 27, 2011 1:06 am ] |
| Post subject: | Re: How to avoid cocked sides when bending on a bending iron? |
I like to put my pipe in the vise not at a flat angle towards me, I like to angle the tip towards me up about 4-5 degrees or so. I can feel the pressure of the wood more evenly on my hands. Maybe workbench height might have something to do with it too. |
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| Author: | TonyFrancis [ Wed Apr 27, 2011 5:17 am ] |
| Post subject: | Re: How to avoid cocked sides when bending on a bending iron? |
Crooked or poorly bent sides are one of the most critical details to correct for either hand or machine bent sides - and yes it certainly happens on many machine bent sides also with excessive spring-back in particular. There are many high end builders who look at this unwanted tension or torsion in the sides as a significant issue as far as tone and voice of the instrument is concerned. This video at the martin factory was really helpful to me, after trying to bend to a line for years. I found the wooden template really successful as a bending guide and so simple. Also notice how their hand bending iron is horizontal - this makes it much simpler to keep the bend at 90 degrees. http://www.youtube.com/watch?v=OaLOsq1G_Bk Side bending starts 1.36 in... |
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| Author: | UkeforJC [ Wed Apr 27, 2011 2:43 pm ] |
| Post subject: | Re: How to avoid cocked sides when bending on a bending iron? |
Thank you all for sharing your experience with me. It is so refreshing to read all your comments. It looks like that I just need to gain more experience on bending. Thanks. JC |
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