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Up Topic Welding Industry / Technical Discussions / Shrinkage Formula
- - By ctacker (****) Date 12-29-2008 21:11
any of you know if there Is any formula I can use for determining shrinkage in some 304 SS. What I have is 6-1/8" bar rolled into a 126.817 OD thats .70 thick, I need to know how much I can get it to shrink using Nitrogen so I can Insert it into an ID thats .005 Larger.
Parent - - By DaveBoyer (*****) Date 12-30-2008 04:42
   I don't offhand know the thermal coeficient for 304, but in carbon steel You would need about 235 F temperature difference to get "skin on skin".

   You said "so I can Insert it into an ID thats .005 Larger" but I am working on the assumption you mean .005 smaller or .005 interference.

    At the sizes You are working with the problem will be getting everything lined up, as that ring will be anything but round, will warm up immediatly on contact and probably will get cockeyed before it is in all the way.

    You might be better off pressing it in at room temperature.
Parent - - By ctacker (****) Date 12-30-2008 05:11
The ID of the part the ring is going inside is Larger, by .005 but we still need to be able to "drop " it in place and .005 is not going to allow for it to just drop in, its a bearing surface. the ring going in has been turned and fixed  so it is holding round, we have had alot of success using nitrogen on smaller parts.

I'm figuring we should be able to get .240 shrinkage if we get it to the boiling point of nitrogen but it will warm fast so we need to be quick and accurate. thats figuring it fron 15C to -196C at 1.9 thou shrinkage per inch.That was taken from a website I found.

I was hoping someone has had experiance with this size of ring and knows a true and set formula for doing the calcs.
Thanks, Carl
Parent - - By DaveBoyer (*****) Date 12-31-2008 03:50
I would temporarly fasten some guide blocks around the bore to get lined up. The issue will be keeping it from getting cocked, if You ever used a Volkswagen jack from the '60s, You know what I mean. A smooth lead in radius on both parts is a good idea, even if it is small. If it were up to Me I would rather work at room temperature and use lubrication than at low temp and dry, and I would use blocking and jack screws to keep it going in evenly. From Your desctription it seems the OD of the ring and the ID of the other part are bearing surfaces, and You need to keep them from getting marred. By the way, I think the figure I gave last night is way wrong.
Parent - - By ctacker (****) Date 01-22-2009 03:30
update: we got the ring in place today, had 2  to drop in, 1 going 3.5' down and the other is at the top, we made a tub for soaking the ring in nitrogen, and a spider to keep it round, also the spider was made to be adjustable in size to shrink with the ring. we got a total of .5 inches shrinkage through the Diameter.
we had porta-powers in place in case of a jam, but never needed them. we got the temp of the ring to -200 before moving out of tub. posting a couple pics.
Parent - By DaveBoyer (*****) Date 01-22-2009 04:38
Glad to see that it worked.
Parent - - By 3.2 Inspector (***) Date 01-06-2009 19:49
I know the shrinkage formula when winther bathing :)

3.2
Parent - - By ctacker (****) Date 01-06-2009 19:51
Thats the "Shrink factor" and some women don't know about that! :)
Parent - By Uncle Chuckles (*) Date 01-06-2009 20:48
Haha, all the women up here in Canada know about it. 
Parent - - By OBEWAN (***) Date 01-22-2009 12:50
The women on Seinfeld don't know about it.  Don't forget how embarrassed George was when the woman he wanted accidently saw his shrinkage!  He went berserk asking Elane about it and she did'nt know either.
Parent - By ctacker (****) Date 01-22-2009 14:44
Thats why I said Women Some Women don't know about it :)
Up Topic Welding Industry / Technical Discussions / Shrinkage Formula

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