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Metric vs. inches


Dear Alex & All,

I have not read much on this thread so if someone has already talked
about this please forgive me.

About three years ago I took a year off of teaching for a sabbatical
to learn more about CAD CAM. I entered a totally new field with a lot
of metric measurements in my head. One of the tool & die instructors
explained a good lesson about measuring to me. Picking up a digital
caliper he measured a part. He showed the length in inches and in
millimeter. The inches had a much more precise measurement. In fact
the parts we had to make had a tolerance of plus or minus .002 of an
inch. There were no available tools or machines (lathes or mills)to
give me a metric equivalent. If any of you have a digital caliper
take a measure a part and go back and forth with the conversion
button and you will see. The metric just measured to .00 of a
millimeter. He even further informed me that when many parts are
drawn the tolerance is .0005 of an inch is requested. Now I realize
many parts do not need that level of tolerance, however with machine
tooled parts coming from all over the world the inch measurement will
be hard to eliminate. Many international sources make American
machine tool parts and the parts are requested in inches.

With CAD CAM entering our jewelry world I would be surprised to see
the metric system change what has already been established in inches.
In my own shop I would love to stay metric for the CAD CAM but the
machines I use are all in inches. I will be posting some more CAD CAM
pieces I made shortly on the gallery.

Best Regards,

TR the Teacher
Todd Hawkinson


Todd This shows how confusing these units can be. 0.01 of 1 mm is
0.01mm. Simple enough, right? But 0.0005 of one inch (or of 25.4mm) is
0.127mm. So in fact the metric calipers are more accurate.Hope this
does not disappoint the ‘inch fans’ too much. :slight_smile:

Best regards
Nils Schwarz
Johannesburg, South Africa


Dear Nils,

I had lunch with our Tool & Die faculty today and he clearified a bit
of our position here in N. America. We’re tool dependent. We use what
our industry supports and the inch system is deeply rooted in the
machine tool trades. We use the measuring tools we have available.
They prioritise the decimal inch. So many industries use machines
based on the inch increments it will be here for a long time. To
convert sometimes is very hard to do. Especially if there are a lot of
figures. How did that Mars exploration go any way?

I also think I have a hard time dividing anything into only 100 parts
and thinking these are really small parts (like 9.98 mm) When this
part in inches is .3930. Now looking at these two numbers you would
think the inch fraction is the smaller number. I’m still learning
remember. And who says you can’t teach a old dog new tricks?

Using a good digital caliper I would always order a 10 mm stone to
metric dimentions. But where do carats fit in? Aren’t those based on
Carob seeds? Are those metric? I do know campanies who order stones
measured in thousandths of an inch because they fit into CAD design
that require those sizes. Those sizes are then made into bezels tooled
to those tolerances.

I certainly want the metric to be our standard and do see more and
more metric measurements in the jewelry trade.

The good Mitutoyo digital caliper I use is either .0000" or .00 mm.
so I have to look at measuring as a draw. With the tooling I am
learning the inch does seem to win though.

Best Regards,
Todd Hawkinson


Hello All: I remember when I was a kid they said that we would be
converting over to the metric system. Well I’ve got kids now and we
still haven’t converted. I worked in the Avionics industry for many
years and we measured everything in inches. Most of the tolerences
were in the 10,000ths of an inch.

Michael R. Mathews Sr.


Hello Nils,

I’m European and I do not mind people using theire system.It’s not a
point of beeing right or wrong,or having more benefit from on system
to an other one.The point is that everybody talks the same language
on this wonderful forum and that over the whole wide world!!Now we
are in the position of speaking 100 % international if we could
manage it to use the same language on measurements,weights,distant or
whatever.I’m belgian and I can’t help that the international language
is english, but I adapted myself.For the same reason,I can’t help
that the metric system is used more and more.So it would be very nice
if we all help to improve this forum by adapting ourself for the
benefit of everybody Regards Pedro


Divide an apple pie into 1/4 or 1/ 6th or 1/12 th…etc…are you
dealing with inches or metric…No… you are dealing with
Fractions…If you can do fractions of a pie… you can do fractions
of an inch. Metric is easier for most people and probably should be
adopted world wide… It doesn’t matter much to me as I was born in
Germany with a French mother, A louisiana Cajun father, a Swiss
stepfather and I work on old Jaguars and brittish motorcycles Just
for the sheer “pleasure”#$%$# of it. As a result, I started with
the metric system, got taught the American system , Had to buy
Brittish imperial tools to work on the Brittish stuff… and I make
Jewelry where there is no standardization at all ( In the USA)
.Oh…and I had to learn all of this stuff in 5 languages including
Thai ! Darn … Now, If we make the world one system, I’ll have to get
rid of the old Jaguar And the 55 triumph 500 speedtwin and THAT will
make the wife Happy :). Just having some fun and throwing my 2 cents
in. No Offense meant to anyone.
Daniel Grandi