PDA

View Full Version : Am I on the right track?



STAN
08-07-2003, 05:28 PM
I need to produce 120 pcs- Tubing 2.625 OD(+/-.020) x 2.500 ID(+/-.016) x 12.500 long. Material is 310 SS. No special finish.

My plan is to use 2 1/2" s/40 welded pipe. (2.875 OD x .203 Wall).

I've never used a lathe, but quick study. If I spend around $1000 on a lathe can I reasonably expect to do this in 50 hrs or so.

My plan would be to cut to length (I have a saw) ream ID. Make locating ID inserts for both ends. Turn the OD.

Will I have the capability to ream? Wall concentricity problems?

I can farm this out, but I want to buy a lathe. But I don't want to get in way over my head and not be able to deliver to customer in 3 weeks or so.

Thanks for any help.

Stan

Evan
08-07-2003, 05:37 PM
Your specs work out to an ID of 2.469 for the tubing. Allowing the max tolerance stated for the part that is 2.484 which is .015 out of spec at the tolerance limit. If you really need the stated tolerance you will have one hell of a time removing .020 or so from the inside of such a piece of stainless tubing. I say farm it out.

The problem will be holding such a piece when reaming with attendant work hardening. The weld will cause problems as well. Turning the OD of (relatively) thin wall stainless will also be a problem. This sort of work calls for a MUCH more expensive lathe and setup.



[This message has been edited by Evan (edited 08-07-2003).]

Al Messer
08-07-2003, 05:39 PM
Be sure and buy a Center Rest to go along with the rst of your accessories. You'll need it if you are going to ream in the lathe.

winchman
08-07-2003, 06:38 PM
Yikes, "three weeks or so" for a newbie to find a "$1000 lathe", get it into operation, buy the tooling, make the required fixtures, etc, etc. Now, that's a recipe for disappointment, if not disaster.

The $1000 lathe isn't going to do anything safely without your being there, and it's going to take at least an hour apiece (a WAG, I admit) for each one on a manual machine. Evan is right--farm it out.

But, in case you decide otherwise, here are some links to photos of a fixture I use for machining thin-walled aluminum tubing. You could make something similar to support the tubing while you turn the OD.

http://www.rcuniverse.com/gallery/showphoto.php?photo=16979&papass=&sort=1&size= medium&thecat= (http://www.rcuniverse.com/gallery/showphoto.php?photo=16979&papass=&sort=1&size=medium&thecat=)

http://www.rcuniverse.com/gallery/showphoto.php?photo=16980&papass=&sort=1&size= medium&thecat= (http://www.rcuniverse.com/gallery/showphoto.php?photo=16980&papass=&sort=1&size=medium&thecat=)

You'll need to cut the pieces a little longer than finished length so they can be gripped in the chuck. Face one end and turn the OD. Turn the part around and cut to the finished length.

If you get the ID done first, the concentricity should be within specs.

Roger

[This message has been edited by winchman (edited 08-08-2003).]

Rich Carlstedt
08-08-2003, 08:11 PM
For such a short run, and loose tolerances,and long bore, Send out the parts to a commercial honer. They do a bang up job, then you can do the OD after and be able to hold good concentricity.

Rich Carlstedt
08-08-2003, 08:26 PM
Have you looked at commercial DOM tube or Stainless/
you might try
http://www.ltv-copperweld.com/pdfs/AutoBro.pdf

Takes a couple of minites to download, but worth the look

Thrud
08-10-2003, 05:29 PM
STAN:
Sage advice - "I don't want to get in over my head"

Not a good "beginner project" - fact is most professional machinists would cringe at the thought...

There are tube lathes that can cut and finish a job like this in one step - farm it out.

ibewgypsie
08-10-2003, 11:43 PM
Jump in, it is just money. With what you learn on this project you will have the rest of your life, priceless.

I got a real good lathe for 700, but I shopped for about 4 months and went 800 miles to get it. I would do it, but I have been learning for about 2 years now.

SteveC
08-11-2003, 11:38 PM
That is a pretty big reamer. I would consider a set-up like this.
Remove the tool post and attach a fixture that will hold the part. Something like a pillow block. Then hold an adjustable boring tool in the chuck that is long enough to be supported by the tail stock. Kinda elaborate, but you can bore very long holes this way.

Steve

STAN
08-13-2003, 09:36 AM
Thanks for all the advice. I think farming this one out is my best option. Exploring a couple of ideas including redraw. I've paid for my drill press and bandsaw with small deals. I suppose the lathe will have to wait for another opportunity.

I think I dodged another bullet.

Stan

C. Tate
08-13-2003, 03:35 PM
Stan,

You can buy this cut to length and made to size from a tube distributor like Marmon Keystone or Tube Sales.

C. Tate

wierdscience
08-13-2003, 07:43 PM
Did I read you correctly in that you need 2-5/8 od by 2-1/2 id?If so thats only a .0625 wall,pretty damn thin to machine,I did it once in brass with special tooling that cut od and id at the same time,but even then it was a bear.
What I think I would do is roll them out of ss sheet and tig weld the seam on a mandrel to maintain concentricity with in limits,still a bear but a much smaller one than machining in a lathe.