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SGR Benchtalk

Temperature and Accuracy

by Stan Ware

I have been playing with what temps do to accuracy in reference to set up of the barrel ready to chamber. I have done three tests now and come up with about the same result. What I do is set up my barrel in the 4 jaw and insert a range rod and dial it in to zero on the range rod with a tenths gauge. This is done about 4:00 or so in the afternoon when everything in the shop is been at 70° all day.

golden gate bridge

I normally quit about 5:00 in the afternoon (don’t tell Suz) and turn the heat down to 65° for the night. I am back out there at 9:00 and check the tenths gauge only to find out that its exactly 1 tenth off. I then turn up the heat to 70° again and check it every hour or so. What I find out about 10:00 its moved back up a half of one tenth is all. When I go in for dinner at Noon its still one half of a tenth shy of where I started. I come back at 12:30 and at 1:00 its back to zero where I started. Obliviously it takes that long for the cast iron mass in the lathe to get back to where it was when I started. Conclusion is that one tenth don’t mean much on the end of a 2×4 but is a lot in a chamber. My advice is either do your set up and chamber the same day and keep the temp the same all day or wait until it warms back up.

stan by coach bud grant

I had the privilege of doing some work for 3M in Minneapolis in their machine shop. It was in a controlled environment and at the time I didn’t think it was that important but if you want to keep your work as accurate and possible it sure is. Maybe another answer is move to a warmer climate !! SGR