[M.D. Holloway]

I guess I didn't give enough info. Here is why:
• Machinery’s Handbook has coefficients of expansion for 41 different stainless steel alloys.
• Of the 41 alloys, the coefficients vary from 5.2 to 9.6 micro-inches per inch-°F of expansion.
• From there, you need to know the alloy, the length of the whatever that you are determining the amount of change, the starting temperature, and the end temperature.
• With a range of the coefficients being as wide as it is, roughly 52%, and the other information necessary the best that I can do is a very rough guess.

My best guess, and it is really a guess, is a minimum of a 50° change between T1 and T2. It is the length of the whatever that is the limiting factor here. If we are talking about something 36” long, then 1/1000” of expansion is easily achieved and the ΔT is not that great. If we are discussing 1½”, then the ΔT gets to be fairly large because the amount of length is fairly short.

This question comes about because I saw a product on the market that "freezes" a bolt to loosen it. I thought it was dumb but it did get me thinking - at what temp do you have to get to in order to actually shrink a bolt? I guess the answer is "It depends..."?