In my steel book it says 1 MM dec. equivalent is .0394 when I x that x 100 I come up with 3.94 but the book says 100 MM is actually 3.937
The decimal equivalent for 100 MM is 3.937 so when I devide that x 100 I get .03937
If I take .03937 x say 78 MM I come up with 3.07086 but the book says its actually 3.0709
What am I missing.
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I have an app on my phone that is a unit converter. Very handy. I can convert any measure of a unit and transfer it to another with a button. Free too.
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converting mm to in, etc.
Originally posted by Portable Welder View PostThanks guys, Yea I finally realized that, I'm just not used to rounding up and was surprised that alro steel did.
When they were teaching us the metric system 30 plus years ago they should have stuck with it.
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inches to mm= multiply by 25.4
mm to inches= divide by 25.4
For most shop work, that is close enough.
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Thanks guys, Yea I finally realized that, I'm just not used to rounding up and was surprised that alro steel did.
When they were teaching us the metric system 30 plus years ago they should have stuck with it.
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.039371
Use .039371 for decimal/millimeter equivalent.
100 X .039371 = 3.9371.
78 X .039371 = 3.070938
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The chart is rounding to the nearest 10thousandth inch.1 MM = .03937 but it is rounded to .0394 for the chart"If I take .03937 x say 78 MM I come up with 3.07086 but the book says its actually 3.0709"Again, this is due to the chart being rounded to 4 decimal places  your 3.07086 rounds to 3.0709.The chart at http://mdmetric.com/tech/cvtcht.htm says for greater accuracy when converting MM to IN  divide MM by 25.4. So, in your example (78 MM to IN)  78 / 25.4 = 3.07086614173 (which would be rounded to 3.0709 in your chart)
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They are rounding up. What are you doing that requires that level of accuracy? That difference is well within the tolerances for cold rolled steel in my information.Meltedmetal
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Simply rounded the last few decimal places to keep it simple. Unless you are measuring precision machined parts there is no need to be exact down to the 4th decimal place.
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