# Interpreting Decimals in the mm state - Off Wall Question

#### mr500

##### Starting to get Involved
We are having a heated discussion on interpreting decimals in the mm state. Correct me If i am wrong but .1 is read as tenth of a mm. .01 is one hundreth of a mm .001 is one thousand of a mm. etc.. etc..

Do not MM fall under the same decimal places as the inch would? ie tenths hundredths thou etc... only instead you say mm instead of inch.

#### somashekar

Re: Off Wall Question

We are having a heated discussion on interpreting decimals in the mm state. Correct me If i am wrong but .1 is read as tenth of a mm. .01 is one hundreth of a mm .001 is one thousand of a mm. etc.. etc..

Do not MM fall under the same decimal places as the inch would? ie tenths hundredths thou etc... only instead you say mm instead of inch.
sounds right to me, .001mm is called micron and .001 inch is called a mill

#### Jim Wynne

Re: Off Wall Question

We are having a heated discussion on interpreting decimals in the mm state. Correct me If i am wrong but .1 is read as tenth of a mm. .01 is one hundreth of a mm .001 is one thousand of a mm. etc.. etc..

Do not MM fall under the same decimal places as the inch would? ie tenths hundredths thou etc... only instead you say mm instead of inch.

You're correct; .1 is one-tenth no matter what system is being used. What is the argument against it?

#### WCHorn

##### Rubber, Too Glamorous?
Trusted Information Resource
Re: Off Wall Question

I agree with Jim that you are correct. Regarding 0.001mm, move the decimal point three places to the right and you have the commonly used "micron" or "micrometer (µm)," a millionth of a meter.

I love the metric system of measurement!

#### Stijloor

Super Moderator
We are having a heated discussion on interpreting decimals in the mm state. Correct me If i am wrong but .1 is read as tenth of a mm. .01 is one hundreth of a mm .001 is one thousand of a mm. etc.. etc..

Do not MM fall under the same decimal places as the inch would? ie tenths hundredths thou etc... only instead you say mm instead of inch.

In addition, "the zero shall precede the decimal pont."
Outside of the USA, instead of the decimal point, a comma is used.

Stijloor.

T

#### True Position

Re: Off Wall Question

You're correct; .1 is one-tenth no matter what system is being used. What is the argument against it?

The problem with this is a lot of machinists/engineers(I might even say the majority in the US that I've dealt with) say 'tenths' as 0.0001 inch. I know it's not right, but I do not see it changing any time soon as long as people continue to work in inch. In MM I often hear people describe a tolerance of +/- .2mm as 'plus or minus 200 microns'. While it seems silly there is less chance for confusion in the long run.

#### Stijloor

Super Moderator
Re: Off Wall Question

The problem with this is a lot of machinists/engineers(I might even say the majority in the US that I've dealt with) say 'tenths' as 0.0001 inch. I know it's not right, but I do not see it changing any time soon as long as people continue to work in inch. In MM I often hear people describe a tolerance of +/- .2mm as 'plus or minus 200 microns'. While it seems silly there is less chance for confusion in the long run.

Yep! We're WAAAAAAY behind....

Stijloor.

T

#### True Position

Re: Off Wall Question

Yep! We're WAAAAAAY behind....

Stijloor.

I don't like the system, but if you start describing an inch dimension of 0.3 as 'three tenths' you won't go long before you're explaining that you weren't saying 0.0003. As to the micron thing, saying a whole number is less likely to cause confusion later. Let's say you have a tolerance of +/- 0.013. You can say: 'plus or minus zero point oh one three millimeters' or 'plus or minus thirteen microns'.

I'm only giving my personal experience, right or wrong, those examples are what people seem to do, at least when I am on the phone with them.

#### Stijloor

Super Moderator
Re: Off Wall Question

I don't like the system, but if you start describing an inch dimension of 0.3 as 'three tenths' you won't go long before you're explaining that you weren't saying 0.0003. As to the micron thing, saying a whole number is less likely to cause confusion later. Let's say you have a tolerance of +/- 0.013. You can say: 'plus or minus zero point oh one three millimeters' or 'plus or minus thirteen microns'.

I'm only giving my personal experience, right or wrong, those examples are what people seem to do, at least when I am on the phone with them.

I know. I was only expressing my concern about the delay in SI Metric implementation in the USA.

Stijloor.

T

#### True Position

Re: Off Wall Question

I know. I was only expressing my concern about the delay in SI Metric implementation in the USA.

Stijloor.

What surprises me are the shops that convert drawings from metric to inch for their operators. While it would be a bit of an adjustment, I can't see why they have not begun converting the hand tools over to metric versions over time. Especially places with mostly digital tools when they can usually work in either with just the press of a button.

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