"Bill Schwab" wrote in message
link.net...
snip--

Dial backlash question: if I advance to the edge, back away to repeat
and then touch again with the dial locked in place from the first pass,
is it reasonable to expect the resulting two backlashes to cancel each
other? I think you've implied that, and it makes sense, but I want to
make sure that I am not getting the wrong idea. I understand that the
dial readings in the backward motion would not be correct.

Bill

That's correct. When you back off, to properly deal with backlash, always
back off too far, then turn to your mark in the same direction as you did
originally. That rule is across the board, whether you're using your edge
finder or positioning. I make it a habit to routinely work from the
left side and back side of parts, so the dial reading is always right
handed, or with the dial. Only under rare circumstances do I not. That
means if you're working from the center of a part, you must keep backlash in
mind as you work the far side of center, and the left hand portion of
center. If you use the same sequence routinely, it becomes second nature
and you don't really have to think about it.

A note he Use your (high quality-buy a good one. I recommend a Starrett
C305R) 6" scale for every move. It will tell you if you've turned the
handle a turn too far, or even catch a mistake if you transpose some
numbers. Carefully applied, you can read a scale to .005" without much
difficulty. That will save you tons of trouble. It is especially
important when you're stepping off holes, where you have a multitude of
chances of making scrap. Use the scale until it becomes routine, just
like working with backlash. Touch your spotting drill or center drill to
the piece, and measure the dimension from your reference point. It takes a
moment to do, but far less time than making a new part. You'll improve
your quality immensely if you follow this advice.

Harold