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Re: [PSUBS-MAILIST] how to machine a big pipe end?



Hi Alec,
 
I just welded my ballast tanks out of similar material. I don't remember where you are from, but in the area of wisconsin I am in I think there are several machine shops that can handle the job depending on the length. Many larger lathles will be able to handle the 12.75 inch diameter. They will then need to use a steady rest to support the end being machined and cut to your specs.
 
I realize that it is an unexpected expense, but I think it could be done for 200 - 300 dollars.
 
Unfortunately when the pieces get larger you have no luck with the back yard guys because their equipment is not usually large enough.
 
Thats the only idea I have. Hopefully someone will have a less expensive option.
 
Best Regards,
 
Jim K
----- Original Message -----
Sent: Friday, November 28, 2008 4:47 PM
Subject: [PSUBS-MAILIST] how to machine a big pipe end?

I have a typical fabrication difficulty, and am wondering if anyone can recommend a tool or idea.
 
The ends of my battery pods that receive removable endcaps have a SS inside shoulder, and were buttered in SS. The shoulder and SS were then machined to a close tolerance to seal with a similar SS ring on the edge of the endcap. When this machining was done, the pod pipe was only about 18" long so that it would fit on the lathe. That short bit has now been welded to a much longer one, and I've also welded on external stiffeners, through-hulls, etc. None of the welding was less than 10" from the machined end, which I thought would prevent heat distortion. One of the pods came out fine, but with the other I was wrong, the pipe end is now an oval.
 
I've tried stretching the short diameter of the oval with a 2 ton hydralulic jack. That corrected it a bit, but I still have about 0.015" to go. This jack can't stretch the pipe any further, it's reached its limit. But in any case, that's such an inexact way of fixing the problem I don't think I could get it properly round to the final few thousandths this way. I think I need to re-machine this pipe-end in place, and obviously it isn't going to fit back on a lathe as is.
 
Ideas:
 
- Cut the pipe again to put the pipe end on the lathe, and re-weld.
- Make a jig that will center on the pipe ID and have a longitudinal shaft, with an adjustable arm mounted to it and a lathe cutting tool on the end of that. Yuck, a lot of work.
- Is there some specialized tool out there?
 
Any ideas are welcome! BTW the pipe is 12.75" OD.
 
 
thanks,

Alec
 
 

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