On 2011-11-20, Jeff Liebermann wrote:
On Sun, 20 Nov 2011 13:38:36 -0000, "N_Cook"
wrote:
An engineer told me never close the jaws of a micrometer or vernier calipers
for storage, leave the jaws open slightly.
True. With gear type calipers, the lubricating grease tends to
migrate to that position. If a sufficiently filthy environment, an
lump of dirt encrusted grease will be left in that position. If it
happens to be at 0.0, then it will be difficult to accurately
calibrate the mechanism.
But he said "Vernier calipers" which have no such mechanism.
Though people tend to lock the slides, so thermal stress distortion
could be a problem with them stored closed and locked.
There are also some minor reasons, such as
the tendency for two parallel surfaces to trap moisture between them
and rust.
Assuming non stainless steel jaws. (I've never seen calipers
with carbide faced jaws, unlike good micrometers.)
[ ... ]
How do they know of any movement of
the jaws when switched off elsewise?
Only the display is turned off. The pulse counting mechanism is still
operating and functional. The downside is that the battery will be
dead in about 6-9 months. Most include a spare LR44 battery. I had
to buy a pile of them to keep my calipers going. Somehow, the battery
is usually dead when I need to use them.
50 batteries for $3.75
http://www.ebay.com/itm/220751739681
There is your problem -- cheap cells. Don't use the LR44 (those
are alkaline batteries), use the SR44 and SR357 (Silver Oxide cells,
with much longer life). Then things will probably last at least six
months in storage. The SR44 and SR357 are pretty much interchangeable.
I don't even know why there are the two series -- though you will often
find them with both designators marked on the same cell or packaging. :-)
I have an expensive set of Starett calipers (both metric and US). I
use them more often than the electronic variety, mostly out of habit.
My most useful measuring tools are my 6" pocket steel scale and a tape
measure.
While I tend to use the digital calipers by preference. Half as
many calipers needed to cover the metric and inch measurements.
Enjoy,
DoN.
--
Remove oil spill source from e-mail
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. |
http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---