1. Tried the formulae, after I found the right coefficients on 2 different repudable sources on the net (you can't be too careful) At -200C, my parts theoretically have 0.001" clearance, zip for practical purposes. UHMW has an annoying characteristic of being as slick as telfon, until you squeeze it a little and then it sticks. I've respecified the holes so I have a comfortable 0.020" clearance at COLD temperatures, downright sloppy at room temperature. 2. Thanks to all you guys for the help 3. this is NOT a toaster - (do toasters get cold? Do toasters use liquid nitrogen? Answer: Does the Pope program PICS? Is Ossama Bin Laden a Nice Guy? ) It is a cryogenic processing system that will be used to make the mirrors on the new outriggers at the Keck observatory. http://www2.keck.hawaii.edu:3636/realpublic/gen_info/kiosk/index.html#Future What else do I have to do when toasters get boring? --Lawrence Lile ----- Original Message ----- From: "John Gardner" To: Sent: Thursday, September 27, 2001 6:14 PM Subject: Re: [OT]: Coefficient of Thermal Expansion > Douglas Butler wrote: > > > > Uh... by dimensional analysis I get the area coefficient of expansion as > > the square of the linear coefficient. If you are looking for square > > inches of hole minus square inches of shaft cross section your answer > > has to be in square inches. > > > > On the other hand if you assume they are both round and just look at the > > diameter of the hole minus the diameter of the shaft the whole area > > thing is moot. > > > > I loved my high school physics teacher, but I think I annoyed him. > > I know the feeling. I frequently shrink steel parts into > aluminum bores - Said Al bores vary in diameter by the coeff > of linear expansion, in this case .00001244 in/deg F, within > the limits of my measuring equipment. > > Maybe toasters are different. > > regards, Jack > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > email listserv@mitvma.mit.edu with SET PICList DIGEST in the body > > -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body