Found this link today that describes the differences between how you talk about numbers in Math class versus the Machine shop. It was actually helpful to me to see it all written out.
So do we all agree with all examples?
There were a few that I hadn’t heard before. IE the ones referencing Millionths
MACHINIST TALK
- In general conversations or math class you may hear numbers spoken one way, in a Machine Shop, you may hear the same number described differently for example:
Keep in mind for the following:
In math class everything is based on 1.0
In a Machine Shop using Inch measurements, everything is based on .001" (one thousandths of an inch)
So, how would we say the following?
0.1000
in math class = “one tenth”
in a machine shop = "one hundred thousandths
WHY? because if everything in a machine shop is based on .001 then there are 100 - “thousandths” of an inch
.0100
in math class = “one hundredths”
in a machine shop = “Ten thousandths”
.0010
in math class = “one thousandths”
in a machine shop = “one thousandths” or “one thou”
.0001
in math class = “one ten-thousandths”
in a machine shop = “one tenth”
WHY? because if everything in a machine shop is based on .001 then there is 1/10th of one thousandths of an inch
.00001
in math class = “one hundred-thousandths”
in a machine shop = "Ten Millionths"
Machine Shop examples:
12.3456 = Twelve inches, Three hundred forty-five thousandths and six tenths
0.12345 = One Hundred Twenty-Three Thousandths, Four Tenths and Fifty Millionths
0.5430 = Five Hundred Forty-Three Thousandths
0.0123 = Twelve Thousandths and Three Tenths
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Seriously - THIS is why I vastly prefer metric when we are talking about ‘tiny’ measurements. These wibbly-wobbly-terms based on some english dude’s shoe size is dumb.
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Please note in all your examples they have four decimal places. So when looking at the tolerance block all of these would have tolerances for parts measured to parts in tenths. Tolerance blocks (where the tolerance is not specified in the field of the drawing either as a ± or as a tolerance band for the upper and lower limit - usually when an asymmetrical tolerance band) usually look something like this:
.X" ± .06"
.XX" ± .030"
.XXX" ±.015"
.XXXX" ± .0020" (note: the last zero is significant, is saying how you round and what precision of tool is to be used.)
These numbers will vary a lot depending on company and what is being made. Surface finish is also usually shown.
On the 12.3456" I think you’d usually hear it said as: Twelve point something. Usually when talking both folks know the feature being discussed and know .1000" when said is “point one” that it really is one thousand tenths. In real life it isn’t that confusing because people are looking at the drawing and know what it is when speaking. “It’s a two tenths over.” or “Undersized one thou.”
Metric is easier as long as you don’t aspire to walk on the moon. For some reason countries that use the easier system still haven’t made it have 50+ years! 
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Well for the broken hell hole of a country China was until they became hyper capitalistic a few decades ago, China is probably going to walk on the moon before our 2nd time because of NASA bureaucracy
Second Country, not second time. US did it 6 times.
I agree they will probably be next - I’ll bet US is first one to Mars. First base camp on moon.
China has done some impressive things - like the US, when a country throws it’s support behind something it can be accomplished.
yes the language of the machinist is thousandths.
However, .0001 is generally referred to as a ten-thousandths or a tenth.
I know that can be confusing since .01 is ten thousands. Notice the difference in spelling? But that what a print is for - not that many people work in tenths since it is difficult to achieve or maintain as a tolerance.