Re: [CAD_CAM_EDM_DRO] gauge blocks was Re: Rolled Ballscrews

I wonder if you all aren't worrying to much about temperature changes.

Lets, see...if the machine and the measuring tools are kept in the shop
together long enough for the temperatures to stabilize, any changes in
length due to temperature changes will be virtually undetectable using
"standard shop measuring tools.

However, if your machine is all aluminum and the tools are steel, then you
"might" have a problem. A 20 degree temperature change will cause a length
variation of .0029" over 12" in aluminum and only .0015" in steel. The
difference of .0014 would then be measurable.

Smoke

> A B grade 81 pc gage block set for $80 does seem to be a bargain...beats a
> $2500 Weber gage set.
>
> I would still prefer to use a series of long secondary standards
> simply because it is less work for a 10 foot way. They are also so easy

to

> make.
>
> But certainly if you used the 1", 2", 3", and 4" gages wrung
> to 10" as a basic primary standard it would work great and you would have

a

> nice gage set after the calibration for only a little more money. For

grade

> B the maximum error for that
> wrung stack would be only a 0.4 thousandth spread. Perhaps not as good as

a

> Starrett micrometer standard, but good enough. It is equal to the error
> from a temperature change of 8 degrees F. The real error would probably be
> much less.
>
> Trying to get .001" accuracy over many feet is not easy.
> Clearly the controller would need to know the temperature.
> Fortunately many parts we would make only need that accuracy over a small
> distance. But it is fun to contemplate
> how to measure micrometer accuracy distances over many
> feet very economically (at least for me).
>
> I guess what we would all like to have is a nice laser
> interferometer. I had a physics professor I used as a consultant a couple
> years ago who claimed he could throw together one from junk parts for

about

> $100. I don't know
> how you would get a long coherence length laser and precise
> temperature control for that price though. Ought to check with
> him again.
>
> Leslie Watts
> L M Watts Furniture
> Tiger, Georgia USA
> http://www.rabun.net/~leswatts/wattsfurniturewp.html
> ----- Original Message -----
> From: <ballendo@...>
> To: <CAD_CAM_EDM_DRO@yahoogroups.com>
> Sent: Tuesday, November 06, 2001 8:36 PM
> Subject: [CAD_CAM_EDM_DRO] 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
> >
> >
> > Addresses:
> > FAQ: http://www.ktmarketing.com/faq.html
> > FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
> >
> > Post messages: CAD_CAM_EDM_DRO@yahoogroups.com
> > Subscribe: CAD_CAM_EDM_DRO-subscribe@yahoogroups.com
> > Unsubscribe: CAD_CAM_EDM_DRO-unsubscribe@yahoogroups.com
> > List owner: CAD_CAM_EDM_DRO-owner@yahoogroups.com, wanliker@...
> > Moderator: jmelson@... timg@... [Moderator]
> > URL to this page: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO
> > bill,
> > List Manager
> >
> >
> >
> > Your use of Yahoo! Groups is subject to

http://docs.yahoo.com/info/terms/

> >
> >
> >
> >
>
>
> Addresses:
> FAQ: http://www.ktmarketing.com/faq.html
> FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
>
> Post messages: CAD_CAM_EDM_DRO@yahoogroups.com
> Subscribe: CAD_CAM_EDM_DRO-subscribe@yahoogroups.com
> Unsubscribe: CAD_CAM_EDM_DRO-unsubscribe@yahoogroups.com
> List owner: CAD_CAM_EDM_DRO-owner@yahoogroups.com, wanliker@...
> Moderator: jmelson@... timg@... [Moderator]
> URL to this page: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO
> bill,
> List Manager
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
>