Turning down Gr. 9 Ti Tube Wall Thickness

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calinb
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Joined: Mon Feb 09, 2009 11:34 pm

Turning down Gr. 9 Ti Tube Wall Thickness

Post by calinb »

I've never tried to do it but recently found these comments in two posts by ECCO Machine.

Here: viewtopic.php?f=10&t=156085&p=971144&hi ... ss#p971120
CWSR is stronger, but if you have to reduce wall thickness, it tends to oblong badly due to stresses in the material from forming & tempering. I spent about 3 hours the other day straightening a piece of 1.5" OD .035 wall I had to turn down to .030" wall, and even though I had a 1.428" mandrel through the 1.430" ID, instead of staying at a 1.495" OD round with maybe .002" variation, the stuff went egg shape to the tune of 1.513" x 1.468" in some areas as soon as I took the mandrel out.
and here: viewtopic.php?f=10&t=139043&p=949749&hi ... ss#p949747
My preference is .070" wall with 24 pitch threads, then I thin the tube out to .040" wall in the middle.
So how does one "thin" a CWSR tube? I was thinking about using grade 9 CWSR for spacers but they need thinning to fit inside a body tube. Does grade 2 tubing work better for spacers? Sadly grade 2 is less available in OD/ID combinations than grade 9 so what about annealing grade 9 tubing or would that distort it too?
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Capt. Link.
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Re: Turning down Gr. 9 Ti Tube Wall Thickness

Post by Capt. Link. »

I read the post and think you should try to make the spacers yourself.He mentions using a mandrel,what if you were to turn and bore to reach the thickness you wish.What if you made each spacer one at a time using the thicker tube to hold the form before you cut it off.Maybe you need to normalize the piece halfway through machining it or afterward as stress is obviously a issue.I respect ECCO's skill but doubt he has unlimited time as he has found a better way.
I have turned and bored Ti cwsr in truing operations without issue.That rarely accounts for more than .005 per-side.You certainly could use annealed or CP-2. The use of spacer elimination techniques comes to mind.
-CL
The only reason after 243 years the government now wants to disarm you is they intend to do something you would shoot them for!
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calinb
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Posts: 61
Joined: Mon Feb 09, 2009 11:34 pm

Re: Turning down Gr. 9 Ti Tube Wall Thickness

Post by calinb »

Capt. Link. wrote: Mon Mar 08, 2021 11:07 am I read the post and think you should try to make the spacers yourself.He mentions using a mandrel,what if you were to turn and bore to reach the thickness you wish.What if you made each spacer one at a time using the thicker tube to hold the form before you cut it off.Maybe you need to normalize the piece halfway through machining it or afterward as stress is obviously a issue.I respect ECCO's skill but doubt he has unlimited time as he has found a better way.
I have turned and bored Ti cwsr in truing operations without issue.That rarely accounts for more than .005 per-side.You certainly could use annealed or CP-2. The use of spacer elimination techniques comes to mind.
-CL
Thanks for reading Ecco's post and replying here with some good ideas, Capt. Link. Using the thicker tube to maintain form and minimize distortion seems like a good thing to try. Yes--I see how the timing of nomrailzing the piece might make a difference too (maybe normalizing before parting off each spacer?) Maybe I'll try those ideas and, if they don't work, I could try annealing the entire CWSR tube before any machining, assuimng I can't find CP-2 in the dimensions I need.

Or maybe I'll get lucky! :)

I'd never even given this issue any thought until I read Ecco's posts but obviously it can be a problem. I'll also review spacer elimination. It's been a few years since I looked at it. What comes to mind is boring grade 5 bar with stepped ID from each end or welding. I'm not a welder beyond basic wire feed skills so I'm avoiding it.
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