Gunner Asch wrote:
On Tue, 18 Feb 2014 08:29:13 +0000 (UTC), Cydrome Leader
wrote:

DoN. Nichols wrote:
On 2014-02-17, Ned Simmons wrote:
On Mon, 17 Feb 2014 18:27:27 +0000 (UTC), Cydrome Leader
wrote:

Cydrome Leader wrote:
I came across a Mitutoyo 187-906 protractor. It appears to be old stock
and unused, but something about it bugs me.

The beam is thicker than the blade, so its not possible to measure 0
degrees by laying the beam and blade in the same direction on a flat
surface. I'm not sure why you would want to do this, but it seemed like
the first test I could run with it.

The blade itself measures 0.6315" thick along the entire length and the
beam section with the protractor is two parallel bars that are 0.636"
thick. When the protractor is set to 0 degrees there is an offset of what
I'd guess to be half that difference or 10 or so mils where the blade
would sit that much higher across a flat surface.

This "error" if it's even one at all would not affect any other reading,
but it just seems odd to me. It this protractor made wrong or is that just
how they work? Can anybody measure theirs just for fun?

[ ... ]

It seems odd to me as well that they wouldn't match to make it easy to
verify zero. I took a look at mine, a Brown & Sharpe old enough that
there's no model number on it, and the blade and the body beam are
also mismatched a bit in width. Though the blade fits and locks
properly, it's possible the protractor and blade didn't start out life
together. The blade isn't marked so it could even be another brand. In
other words, not much help here.

And -- I have an old Starrett with two blades, (long and short),
and they both have the measuring blade retracted a bit between the two
beam blades. It appears to have been standard practice.

*But* -- doesn't yours have the extra arm which mounts on the
main beam at 90 degrees? *That* can slide to contact the measuring
blade at 90 degrees to verify zero.

I can't find the newer one at the moment -- the one with the
satin chrome finish (easier to read) and only one blade.

Enjoy,
DoN.


It guess it sounds like this is "normal" behavior for these things.

Anybody else have stories of unexpected instrument or tool limitations?

Digital multimeters bug me the most. I keep hitting unpublished
limitations of them, over and over again. It recently got annoying enough
that I had to get an analog Simpson 260 series meter. It may not have the
precision of a DMM, but it doesn't get "confused" either.

Hell..I have at least 5-6 Simpson meters...from the 260 through the
270..including the 261, and the 260-8

I went to Fluke digitals years ago and havent looked back.

the zero ohms knob and selection of every range with the test lead jacks
is a real throw back for sure. The fluke is still the one I'd grab first
for most stuff.