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Doublereed Archive - Posting 000080.txt from 2008/02
From: John Towle <gtowle839@-----.net>
Subj: Re: [DR-L] micrometers
Date: Thu, 14 Feb 2008 17:22:11 -0500
I agree, David Morely. I've got flat feeler gauges &
wires. The wires (round) are easier to measure, at
least when using a caliper. Flats are fine for valve
adjustments on motor cars, but probably not much good
for anything else. Also, for adjusting spark plug
gaps, the wires work best.
Out of curiosity, where does one get dowel pins?
Thanks,
Best,
john
--- David Morley <dmorley@-----.net> wrote:
> Well, it's a day for Davids. Mr. Crispin is
> correct in asking for
> more information about what you've got. If it is a
> sliding jaw device,
> it is a caliper (either Vernier, dial, or digital -
> dependent upon how
> it displays its motion). A Dial Indicator has a
> sensing barb that moves
> in and out of the dial body, and the whole thing is
> usually mounted on a
> base block with a rod running vertically. These
> too can be mechanical
> dials, or digital. No idea what a brass jobs with a
> screw doo-hicky
> is. A micrometer will have a fixed jaw, and a
> movable jaw that is
> driven by turning the end of the spindle held in a
> c-shaped frame.
> If your two micrometers are showing a constant 0.1
> mm error when
> measuring a variety of objects, I'd suspect one (or
> both)of them is not
> zero'ed properly. Screw them down to a closed
> position (they should have
> a smaller knob at the end of the spindle that
> ratchets - clicks - so you
> don't over-tighten the micrometer. They should
> indicate zero. Zeroing a
> digital is simple - there will be a button to press.
> Zeroing a
> mechanical (Vernier) is a little trickier, and
> usually involves
> unlocking the spindle with a small wrench that
> rather looks like a
> distorted tuning fork - should be in the box that
> the mike came in.
> For a very quick reference, a US penny is
> measuring 19.00 to 19.02
> diameter, and 1.39-1.40 thick at Mr Lincoln's ear.
> Feeler gauges are
> okay, but thin, and stacking them up can introduce
> error. Gauge blocks
> are probably the best reference, but may be hard to
> find without
> visiting a Tool and Die shop. Dowel pins are easy
> to find, and usually
> very accurate, and would do for a reference. Hope
> this helps.
> David Morley / Adam Shaper Tips Ltd
>
>
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