gauge blocks was Re: Rolled Ballscrews

Doug,

LOTS of measurements are made using "inchworm" techniques...

The original "suggested" method also only covered a few inches with a
"single use" tool (the calibration bar). My post was to alert to the
fact that once you buy the ground stock, take the time to make copies,
etc., you might just as well have something eminently more useful for
the long(and short) term.

There have already been a few posts in this thread (and we have
covered this before; check th earchive) about how to "inchworm" along.
The jo-blocks will facilitate this quite readily, and with much more
accuracy than the suggested methods.

For another way, How about using the cnc machine to drill a series of
regularly spaced holes in some fairly stable material. tap these holes
(by hand if necessary) and then use a bunch of drill bushings (if
ultimate accuracy is important) or shaft collars/bushings with washers
as "old-time" jig buttons. these are then "adjusted into" the required
level of accuracy(a great use for the jo-blocks) and the resulting
"standard" of whatever length is needed is then fixed to the cnc
machine table and approached by the spindle (with an indicator
mounted) and any variations from ideal will become immediately
obvious.

Hope this helps.

Ballendo

P.S. the ladder block is also a good idea! You can use the jo-blocks
to determine if the "slots" are where they are "supposed" to be, and
you won't need the cmm "buddy"! However, the fact that you are
measuring the resulting CUT of the tool MAY OR MAY NOT give you the
"real" specs, as there may be variations due to material hardness,
cutter wear, etc. The tool button technique eliminates this type of
error.

--- In CAD_CAM_EDM_DRO@y..., "Doug Harrison" <prototype@c...> wrote:
> >
> > The price of full 81 pc. "B" grade(shop grade;+-/50
millionths)Gauge
> > block sets (Jo-blocks) has come down so far as to make them a good
> > choice for a serious hobbiest. Going this route will cost a bit
more
> > than 30 bucks(about 80), but you also will have a VERY accurate
> > standard for all your precision measurements... And you didn't
need to
> > buy the ground stock, and spend time sanding/sizing.
>
> But the Jo-blocks won't stack up to more than a few inches - not
much good
> on an 8ft table. Another solution is to square up the ends of some
bar
> stock without regard to their exact length. Then con somebody into
> measuring them on a CMM at work. I've pulled this one off a few
times.
> Nobody seems to mind. The bars don't have to be any particular
length as
> long as you know what length they are.
>
> A better tool would be a ladder block as shown in Moore's book. For
our
> purposes, a piece of square bar stock with transverse slots milled
every
> inch or so down its length would work. Take it to the same nice guy
with
> the CMM and get the left (or right) face of each slot measured and
recorded.
> Again, exact one inch increments aren't necessary. Just don't stamp
the
> numbers in the bar after it is measured.
>
> If I recall, Nyquist says you can move the bar and take measurements
between
> the previous ones to improve the quality of your map.
>
> Doug