I have read to put it in the freezer and to heat it up. Which has worked? I'm not sending my brand new gun back to s&w yet. Because they are also closed until January 2nd. I'm going to go out and shoot tomorrow anyway. And have the Smith look at it while the so he can break all his Allen wrenches. Lol
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The bond between two pieces of metal, in this case the metal of the screw and the metal of the frame it is screwed into, can be broken by changing the temperature of one of the metals. Heat causes metal to expand, cold causes it to contract. Different metals react at different time rates, especially if they are of different sizes. The difference in the expansion or contraction can/will cause the bond between the two metals to loosen. Because the frame is larger than the screw, temperature changes will effect the frame slower than the screw, thus causing the mating surfaces of the screw and frame to separate or loosen. Instead of putting the pistol in a freezer, I would try canned air propellant, which can freeze the smaller screw quite quickly (and your fingers if you aren't careful!). After spraying, by tilting the can so the liquid propellant comes out instead of the air, let the gun sit for a few minutes to give the cold a chance to spread to the threads and cause them to contract.
In the case of a screw in a larger frame, heat generally is not the answer. As stated above, heat makes the metal expand, which will tighten the bond, not loosen it. The exception to this is when a thread locker is used. Thread locker, such as Loctite work by filling the microscopic voids between two threads and hardening to prevent the thread from loosening during use. This bond can be broken/softened by use of heat, hence the recommendation of using heat when a thread locking agent is used.
As a note of interest, heat can also be used to tighten threads. Large threaded rods were used to hold presses together at a plant I worked at. I'm speaking a rods that were a foot in diameter. They were threaded into the bottom of the press, the top of the press put into place, then heat applied to the rod until it was glowing red. The top nut was then torqued into place and the heat removed from the rod. As the rod cooled to ambient temps, it shrunk, increasing the torque on the rod considerably. Needless to say, when taking the press apart, the reverse had to be done. Just another example of the pieces of useless information my brain retains.
