# CAD CAM & Metric vs. inches

Hey Nils,

You’ve got a great name! My son’s name is Nils. On my digital
calipers the metric decimal only goes two spaces and the inch goes to
three. I haven’t seen a digital caliper that goes three digits in the
metric mode. Maybe we’re too used to zeroing out to inches and not
the 25.41. Also the inch gives us 5000 parts on these gauges.

Maybe all the CAD CAM experts could comment on this one.

Best Regards,

TR the Teacher
Todd Hawkinson

`````` I haven't seen a digital caliper that goes three digits in the
metric mode. Maybe we're too used to zeroing out to inches and not
the 25.41. Also the inch gives us 5000 parts on these gauges.
``````

You really think that degree of precision is needed to do the average
piece of jewelry? .01 mm difference only equals .003937 inches.
.003937 inches = .0999998 mm.

``````   inches x 25.4 = mm
mm divided by 25.4 = inches
``````

Splitting that hair pretty close isn’t it? Most jewelers I am
familiar with consider close good enough.

In response to the comparisons of english to metric scales and the
correllation between the number of decimal places carried it becomes
necessary to compare the smalest elements of each.The conversion of
.01mm=.0003937inches on the other side .0001inches ,the smallest unit
a person can describe in the four place inch system is also
microscopic in relevance.If the scale on the readout is held to .0005
then the difference to .01mm is only one-ten thousandths of an inch
or one four-hundredth of a millimeter. A sheet of paper is typically
.005 inch thick and these two scales at the given decimal places
describe dimensions 20 times thinner!! Truly microscopic. As a
toolmaker I have produced stamping dies, fixtures,injection molds and
even gages and the most demanding tolerances were
typically+or-.0005inches or.013millimeters. If you wanted to
stamp a disc out of 30 gage sterling sheet you would have a clearance
gap of about .0005inches between punch surface and die opening when
they entered or mated up. And it is important that your equipment and
measuring instruments have greater accuracy than the tolerancesyou
work to.

Cache in Arlington Texas
@CaChEtex
toolmaker to artist and artisans

Aloha All, If you are working with a CAD/CAM System it is even less
important, as the system is intuitive. Basically check the box to the
measurement system you care to work with (mm or inches). Personally,
millimeters is more accurate (and has much less zeros), besides we
are jewelers, and it makes more sense.

Best Regards,
Christian Grunewald
Precision Modelmaking Technologies
Hawaii
(808) 622-9005