On Nov 13, 9:33*pm, "Michael Koblic" wrote:
...
(NB if you lock the spindle it changes
the Z-position by about 0.010-0.015"! They have a sort of back-stop bar
which I suspect is an afterthought - it is not mentioned in any of the
manuals)
....
Michael Koblic,
Campbell River, BC

The new RF-31 I bought for Unitrode shifted by up to 0.005" when
locked. I had to mill some shims to better than 0.001" and spent close
to an hour futzing with the damn mill without success, then took the
parts home and milled them on my Clausing.

The Clausing isn't always accurate in the Z direction either, probably
due to wear and the old Wilton vise. I have to tap the work down while
tightening the handle, then check the parallels under the work for
looseness.

You can change the height of work in your mill with two small
adjustable parallels. Set them to some even-numbered size, mill close
to finish dimension and measure, raise the parallels to take up the
difference. You will need a stop on the fixed jaw of the vise to
relocate the work after loosening the vise but that's a good thing to
have anyway. I tapped the cast iron on the left end of the fixed jaw
and screwed on a small plate that can be swung out of the way. I set
the dials to 0,0 with a 1-2-3 block pushed against this stop.

The less you spend on a machine, the more you have to understand and
cope with its problems. You learn what it can do easily, or with
difficulty, and design accordingly. On a mill-drill the axes may be
measurably out of square with each other.

Since the RF-31 wasn't mine I didn't disassemble it or add a Z
indicator but I've found poorly machined small parts on other import
machinery that were easily cleaned up or replaced. Especially on the
older ones it looked like the major parts were made fairly well but
the minor ones had been filed out in someone's kitchen. PBS once
filmed a family making Toyota taillight lenses at home, apparently a
common practice that substitutes for providing daycare.

Jim Wilkins