Wiley Horne -- So. Calif.
>Joel,

Still looking for help. Maybe I'm asking a dumb question, and if so let me know. I still can't get my head wrapped around how scraping cures a small amount of convexity. Say someone has put a slow 1-2 thou convexity on a plane sole, sideways and/or longways--but the sole is also very smooth. And hands it to a machinist to be scraped flat. What exactly does the machinist do? I can't believe the work can be laid on the reference plate in such a controlled way that _the ink_ would reveal the convexity--wouldn't the ink instantly be all over the plane sole?

I understood Thom's explanation that wiggling the plane would be a good test for convexity. I buy that story--but is that what machinists do to detect slight convexity?

I'm not even questioning where reference plates come from that are good to the 5th decimal place, as claimed somewhere in this thread.

Wiley