In this post:
I was trying to calculate the different expansion rates of steel and alumina to figure out how much thread slop I would need in order to screw the TIG nozzle onto a steel nipple.
There are two problems with this analysis.
The first problem is that I have done the calculation 3 times, and come up with 3 different answers. So, double check my math before you trust these numbers!
I now believe that my original post was off by a factor of 4, and that the actual differential expansion would be 0.15 mm for a 25 mm nozzle diameter and a 1500 C temp. change.
The second problem is logical. I was just thinking about the diameter. However, the threads will presumably expand in length as well. I don't know what the length of the threading is. If it is less than or equal to to the nozzle diameter, then the above would be a safe estimate.
I have tried to find out exactly what kind of threads are on the end of a TIG torch than can use the 15/16" nozzles (#15), but so far I am coming up dry.
PS: It appears that the problem in my original post occurred when I messed up the multiplication of 4* 25/1000.