[Files] Re: micrometer source for pianotech (Modified by KentSwafford)

[Carl Meyer]

All this chatter about micrometers makes me want to say I believe in the
Murphy law about precision.

"Measure with a micrometer, mark with chalk and cut with an axe."  Works for
me.

I have about three micrometers.  Seldom use them.  One is a wall thickness
that works well for strings.  It is difficult to measure scales period.

I've long used a dial caliper for it.  Caught hell from jumpin' Joe Garrett
of the tool police for being too cheap to buy a micrometer.

I think a caliper is plenty accurate for measuring wire.  After all we are
mainly checking an original scale and one or two thousands make little
difference on the graph.  We really just want to see the general shape of
the tension/ inh curve.  Pscale then give an accurate dimension for the new
strings which is the important thing.

I won't use a digital caliper because my eyes are analog.  To measure a
round item accurately you need to rock the caliper to minimize the reading
to assure the jaws are flat on the surface.  You need to put a bit of
pressure on the jaws and watch the dial.  When the needle dips to minimum
you have an accurate measurement.  That is hard to do with a digital
readout.  I would wear an analog watch if digitals weren't so much cheaper.
I have to convert two forty five to a quarter to three in my head.  Oh Well.

Now here is a picture of a caliper before and after that I use for strings.
I found these calipers at Harbor Freight for $7.95
on sale.  I bought several.

You can see that I don't have to pull the string up with a hook to measure
and I can measure the wrap in place by rocking the caliper back and forth to
minimize the reading.

It took me an hour to grind the thing to shape.  It needs to be kept cool or
it might warp.  I found that the jaws were not quite flat against each other
and created about one thousands error so I had to pull strips of fine
wet-or-dry through to correct that.  This is a single use tool basically but
I tend to use it a lot if it's laying around and it works fine for most
uses.

Carl Meyer Ptg assoc
Santa Clara, Ca.

----- Original Message ----- 
From: "Ron Nossaman" <rnossaman@cox.net>
To: <files@ptg.org>
Sent: Wednesday, September 29, 2004 5:38 AM
Subject: [Files] Re: micrometer source for pianotech (Modified by
KentSwafford)


>
> > The calipers don't work well on the wound strings unless you can get
> > it past the knife edge tip, otherwise they slip between the windings.
> >
> > I find that the accuracy is the same as the anvil type, unless my eyes
> > are playing tricks. [I'll double check after the strings are out]  I
> > have the plain style, not dial or digital.
>
>
> Calipers work better if you lay them down on the wrapped string some,
> to span the gaps. Also, squeezing the jaws together on the wire close
> to the point of contact, rather than using the thumb wheel eliminates
> the spring of the jaws, keeps everything square and helps accuracy.
> That's measuring pretty much anything with calipers. It depends on how
> repeatably accurate you need to be.
>
> Or you can make a snap gage out of a cheap dial indicator that works
> nicely. Someone, I don't remember who, used to sell something like
> this. Again, laying it down and gently squeezing the jaws onto the wire
> or wrap gives best results.
>
> Whatever you use, measuring wrapped strings, make sure you're far
> enough out on the wrap to be past the core swage. Yea, I know, DUH,
> but...
>
> [Photo at:]
>
> http://tinyurl.com/5jgy3
>
> [Direct ptg.org URL:]
>
> https://www.moypiano.com/ptg/files/attachments/70/2e/16/4d/snapgage1.jpg
>
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