making out-of-round pipe round

Question

making out-of-round pipe round

321carl (Mechanical)

(OP)

16 May 06 21:03

I have 6" schedule 10 pipe (6.625" O.D., 0.134" wall) that is out-of round. The pieces are about 24" in length. Can any metal fabricators/formers make this pipe truely round? I prefer not to turn the pipe.

Alternate question: does anyone know a source for precision round schedule 10, 6" pipe?

Thanks in advance,
--- Carl

arto (Mechanical) · Answer 1 · 2006-05-17 16:28:28

how about hydraulic cylinder tubing?
Ryerson used to list it w/honed ID up t0 6"

MikeHalloran (Mechanical) · Answer 2 · 2006-05-17 20:51:42

How round do you need it?

A marine exhaust shop will have a slip roll big enough to true up that stuff. The guy who runs the slip roll can probably true it up as well with a mallet.

Marine exhaust tolerance is the width of a line produced by a dull Sharpie. If you need it better than that, buy thick wall pipe and turn it, or buy tubing.

Mike Halloran
Pembroke Pines, FL, USA

321carl (Mechanical) · Answer 3 · 2006-05-18 12:00:02

Arto, MikeHalloran,
Thanks for your responses. I am looking into hydraulic cylinders. As to how round it has to be, I'm trying to figure that out now. Off the top of my head I would say .020". The current schedule 10, 6" we use is out of round as much as 0.100"
--- Carl

arto (Mechanical) · Answer 4 · 2006-05-23 15:30:21

hmmmm. ASTM A999 lets 'em send you thin-walled pipe 1.5% of OD out of round =0.099" - sounds like that's what you're getting

MikeHalloran (Mechanical) · Answer 5 · 2006-05-23 18:54:57

"Industry Standard Tolerances" in most industries allow shipment of stuff you wouldn't expect to receive. In some industries, e.g. aluminum extrusions, you can pay a little extra and get tighter tolerances.

On the bright side, sort of, thin wall pipe is flexible enough so that you can force it to be as round as you want to, with external restraints or manual processing. Given the way the stuff is made, it's really not likely to ever be perfectly round, and for most applications, nobody cares.

This might be time to review why you specify what you specify.

Mike Halloran
Pembroke Pines, FL, USA

griffengm (Industrial) · Answer 6 · 2006-05-26 13:54:02

321Carl,
My experience with "thin" wall tube and pipe has been that it may be in spec in longer lengths but, when cut to shorter lengths, it will self-adjust according to local stresses.
Not sure of your application but we have found that adding a rib sometimes helps to true diameter. Depending how much $$ you have, you might try requesting an anneal after cutting.
If it were in our shop and we needed just a few pieces I would put it on a slip roll with 2"-3" rolls and roll it for a few turns. Not super precise but it often gets the job done.

Griffy

MikeHalloran (Mechanical) · Answer 7 · 2006-05-26 20:04:32

Griffy brought up a good point. If your 2 foot pieces are cut on a bandsaw, that alone could distort them badly, thanks to the standard powerful rectangular workholding vise.

Mike Halloran
Pembroke Pines, FL, USA

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making out-of-round pipe round