On 2011-11-20, amdx wrote:
On 11/19/2011 9:01 PM, P E Schoen wrote:
I have two Harbor Freight digital calipers, item #47257, and I've had
problems with one of them especially, where the display will go blank.
It seemed to work sometimes if I squeezed the enclosure, and I thought
it was a bad battery or bad connection. But a fresh battery didn't work.
That's why I like the Dial calipers vs Digital Calipers, no concern
about batteries or electronics.
But -- dial calipers are vulnerable to two problems.
1) Drop or bump them and the pinion will disengage from the
rack and shift to give a wrong reading. You can work around
that by rotating the dial to re-zero it, but past a certain
point, it gets to be awkward to read.
2) Small chips can get engaged in the rack and the zero point
will shift every time you pass that point.
Vernier calipers don't have these problems, but are more
difficult to read with aging eyes and poor light.
Yes -- there are ways to fix both, but a lot more fiddly than
fixing an exhausted battery on the digital calipers.
And the digital calipers have two other advantages over dial and
Vernier calipers:
a) Switch between metric and inch modes at the push of a button,
even converting readings already locked in. (Actually, some
Vernier calipers have both scales, so this does not apply.)
b) Ability to reset the zero where-ever you want, so you can set
it to zero on a target dimension, and then read how much you
need to machine off in a lathe to see how many passes before
you are close enough to do serious measurements. You can even
keep a calculator handy to divide by two depending on whether
your cross-feed dial reads in diameter or radius.
c) (O.K. Three for some people. :-) -- the ability to transfer the
measurement to a computer (without typing errors) for statistics
or other similar processing.
(Dial Calipers, Item # 66541, Out of Stock)
Although a couple years ago HF had the 6" Digital calipers on sale for
$9.99, I bought two. They are still in the boxes and I use my Dial
calipers. I think I might give one away as a Christmas present.
I have three 6" (150 mm) digital calipers, and a 12" (300 mm)
digital caliper. (Not counting two old B&S 6" ones which require
mercury cells for power, which are made of unobtanium.)
I also have a two dial calipers -- a 6" Phase-II, and a 150 mm
Starrett.
And two Vernier calipers -- a 6"/150mm and a 24" (I forget
whether that one has metric units as well.)
However -- the ones which I reach for most of the time are the
digital ones -- because of the memory feature and the ability to switch
measurement systems to match what I am working on and with.
One 6" digital stays near the main lathe (12x24" Clausing) and
one near the little CNC lathe in the opposite corner of the shop. The
cheapest digital ($18.00 at a hamfest) lives up here by the computer for
when I want to measure something quickly.
I keep a spare cell (or set as appropriate) in the case of each
digital, so I am not out of operation for very long if the cells in the
caliper go bad.
The dial or the Vernier get used when I expect to be away from
batteries for a while -- or in case the production of batteries ceases
thanks to some apocalypse. :-) (Or the 24" one for when I need to
measure beyond the range of the 12" digital.)
Enjoy,
DoN.
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