Benchtalk

Temperature and Accuracy

by Stan Ware

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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.

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.

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