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turning thin walled tubing

paulwag

Plastic
Joined
Dec 12, 2017
Location
madison
I am looking for some help with a couple tubes that I need made. they were made in the '30s with a external upset on them so they could be internally threaded and the rest of the id stayed the same. i am not having any luck with any manufactures with such a small qty.

The tube is 2.125" id and 2.5 od needing to be turned down to 2.25" 9" out of 12" length (finished) material would be prehoned st52.3 or 1026.

Is it possible to turn it down to a .0625 wall on a lathe without to much distortion?
 
Maybe not particularly useful for this application but some decades ago I used to mill weird configurations in thin wall aluminum waveguide (.450 x .900 x .050 wall IIRC). There would always be deflection and some of the stuff was high precision (deburring the interior was a massive PITA, too).

Ended up using some green, waxy substance (like the stuff for proving CNC programs ?) melted and poured into the waveguide. It set up hard in twenty or thirty minutes and was very rigid at room temp. After machining, moderate heat allowed the stuff to drain out.

Can't recall the name ("tooling compound" or something like that ?). Never used it again but it was sure useful for waveguide !
 
These scream mandrel. You have options, Press fit, heat shrink, expanding. If you only have a few to do then the filling it up trick would work great, use cerrosafe, lead, bismuth or other lower melt alloy. Cerrosafe is nice because it melts rather low. ~160F.
 
Shouldn’t be huge problem even without mandrel. Just pack the tube with shop rags, rubber bands or whatever to stop it ”singing” during cut.
 








 
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