"Pete C." fired this volley in news:4dd2914a$0$10550
:

Most people use a dial indicator and map the screw an inch at a time.


Not hardly, Pete. I've watched that procedure before on big VMCs. You
want not only "localized" errors, but cumulative errors to be mapped.

As Ed stated below, the Japanese techs were using laser devices. The could
map a 6' travel to half a tenth, cumulative, easily. (I'm betting it was
better than that)

LLoyd