# Bending CPVC

• posted on March 2, 2007, 11:51 pm

How tough to bend CPVC with heat?
I have to bend an 18" radius for a project.
Any problem?
Tips, suggestions?
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• posted on March 3, 2007, 1:57 am
John~

The outside of the bend has to stretch,and metal does that(within limits),but plastic is not going to.
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Jim Yanik
jyanik
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• posted on March 3, 2007, 4:29 am

Metal deforms plastically to bend, either stretching on the outside radius or compressing on the inside radius. In both cases the dimensions of the metal have been changed to accomodate the plastic deformation. The amount that the metal can bend depends on the radius of the bend and the thickness of the metal plus the modulus of elasticity inherent in the metal.
Plastic behaves the same exact way, except that heat must be applied to facilitate the deformation - hence the term thermoplastic.
Metal is easier to bend under normal conditions, plastic is more flexible under controlled conditions. The problem with plastic under heat is that gravity can make a mess of your intentions - sagging the plastic where you don't want it to sag.
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• posted on March 3, 2007, 10:56 pm

Actually it does both. There is a formula for figuring this out (in my machinist book, but it is packed away right now), somethign like a 60/40 split up to a certain diameter.
In both cases the dimensions of the

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• posted on March 4, 2007, 2:07 am

I realize that, I didn't phrase it well. I was more referring to that one side stretches and the other compresses depending upon what direction the bend goes.

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• posted on March 3, 2007, 3:20 am
On Mar 2, 3:51 pm, John~

Yes, it can be done. I don't redcall the specific heat but back in the M.E.N. days before they went yuppie there was an article using antifreeze to get the temperature up to the required level. Probably also need a form to bend it around, i.e., not freehand. Google might turn up something.
Harry K
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• posted on March 3, 2007, 3:55 am
There was an article about bending PVC, filled with sand, vented caps, etc. After the reminder to use preformed turns if possible. Along with the reminder that burst strength would be reduced.

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• posted on March 3, 2007, 3:21 am
On Mar 2, 3:51 pm, John~

Just remembered. Your 18" radius sounds awfully close to a 'slow bend' in electrical plastic conduit (the gray stuff). Maybe that could be used.
Harry K
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• posted on March 3, 2007, 5:28 am
On Mar 2, 3:51 pm, John~

I just did a quickie google search for term 'bending pvc pipe' at least one page is there from special tools to use to the home owner diy process.
Harry K
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• posted on March 3, 2007, 6:12 am
On Fri, 02 Mar 2007 23:51:04 GMT, John~

If you don't need a lot of strength, get a hula hoop and use that.
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• posted on March 3, 2007, 6:16 am
mm wrote:

Pack it with sand before heating .. .. it will (usually) prevent kinking .. .. .. GO SLOW !! !! !!
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• posted on March 3, 2007, 3:43 pm
wrote:

That's a pretty good suggestion really - use what's already available.