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bevel protractor question

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?

Reply to
Cydrome Leader
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I called mitutoyo today and the support guy didn't have one his hands to play with to confirm that the vernier protractor can't really measure a 0 degree angle of a flat surface. He said the digital ones can measure this though. Measuring any angle other than 0 is still possible, so it's not like the protractor is completely broken.

It still seems a bit weird, and I'm trying to confirm if this is normal or not before either keeping or returning the thing.

Reply to
Cydrome Leader

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.

Reply to
Ned Simmons

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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.

Reply to
DoN. Nichols

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.

Reply to
Cydrome Leader

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.

Reply to
Cydrome Leader

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