.002 English or .002 mm? Very big difference. .002 mm is only about 80 millionths of an inch. Autocollimators are measurement devices used to measure flatness on a surface plate. It is called "shooting the plate". Autocolliminators are electronic now, and very accurate. They aren't hard to use, but pretty fussy - and the surface is going to have to be pretty smooth. I believe that the machinist handbook will give instructions, and a description of a grid pattern to use. A plate that large is going to flex, gravity wil affect it. So will heat. And after moving, it will probably change some more. I would shoot it after it has been installed, if it is a critical use item. A couple of items come to mind:
1) the plate should locate on 3 points. More is not better.
2) the plate clamping should be limited to the area within a triangle formed by the locating points.
3) A Michigan outfit, Mitchell surface plate, can check it for you, and they have certs. I guess that $500 or so would cover it? They used to do our plates when I worked for GM. I don't know where you are at, so I don't know if that is practical. There are other folks out there, but they are the guys we used to use.
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Today's Featured Article - Tractor Profile: Allis-Chalmers WD45 (Gas Version) - by Staff. Beginning production in 1953, the WD45 had the same general look as the WD tractor which was produced earlier - but was much more powerful. This was due to the new 4-cylinder "Power Crater" gasoline engine with a 4 x 4-1/2 inch bore and stroke. Some people feel this was one of the most significant tractors offered by Allis-Chalmers in those days. Nothing in its weight or power class could match its performance. In 1954 they began offering the WD45 with the new "Snap-Coupler&quo
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