Hand Bending tubing

#1
Hey guys!

I'm considering a scratch build for a simple mini chopper using 7/8" tube but I've only ever worked with square tube before. Is it possible to hand bend 7/8" in a jig or over a homemade mandrel of some sort? If so, is cold bending ok?


Thanks for the help here!
 
#2
You might be able to get away with a conduit bender. 3/4" emt is very close to 7/8" O.D., so if the tubing you're planning to use isn't too thick of a wall dimension, you may be able to strong-arm your bends.

Roger
 
#3
It can be done but the bends wont be definitive. The tubing will flex and bend beyond the bend causing a slight bow if you don't have a follower to push or back up the tubing close to the bend. A conduit bender is a viable alterative and will give a decent bend but the radius is a little large for a minibike frame.

Here is an alterative if you have the means. You can sand bend the tubing if you can weld and have a good heat source. This is an old world method that has been used for many years in Europe. All the race car headers were built this way in Europe from the 50's into the 70's. Mind you these were built in cottage industry blacksmith shops. Pure artwork when done correctly.

https://rorty.net/news/sand-bending-exhaust-tube

A tubing bender with correctly sized dies will support the sides of the tubing so that it doesn't blow out and flatten as it is bent. Also it will push the tubing around the die to keep the tubing straight beyond the bend.

Here is a link to a JD squared bender. A very good bender at a reasonable price. It will give you very good bends over and over.

https://www.jd2.com/model-3-bender
 
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#4
Great news. Thank you both for the responses. I'll try to find some scrap to give it a shot first. It's encouraging to know that I should at least be able to use a conduit bender to get to 90 degrees. The frame I want to make will have one 90 degree bend and its radius is not too important. The other two bends will need to be over 90 degree bends and are more important but maybe I could just bend to 90 or whatever the conduit bender does comfortably then hand bend around something smaller to support the tube.

I appreciate the help.
 
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