Hello, I’m Jim Salsbury with Mitutoyo America Corporation and welcome to the

Metrology Training Lab. In this episode, we are going to teach you how to speak

like a measurement professional we are often dealing with small numbers in this

business tolerances ayres deviations uncertainties most of the values that

are important to us in dimensional measurements are smaller than the

thickness of your hair these little numbers have multiple zeros after the

decimal points which makes speaking them difficult you don't want to be saying

something like zero point zero zero zero zero five huh to me tall gets lost after

hearing that second zero in both inch and metric units our industry has its

own language and some of it's a bit unwritten and unofficial slang terms

but those special terms can be very useful in everyday conversations we've

put together a technical bulletin on this topic you can easily find it on the

on-demand section of our website in this episode we're going to run through me

through some examples of this language by looking at common measuring

instruments starting with this digital caliper as shown on this digital display

of this caliper the resolution is zero point zero zero zero five inches and

even though I just said zero point zero zero zero five inches I would never say

that in fact just saying that now makes me a bit uncomfortable though the units

are in inches in practice we work in a world where the base unit is a

thousandth of an inch as shown in the second caliper the

tenths – hundredths - thousandths decimal place is one, and we would read this as

one thousandths of an inch, or often simply one thou. I would never write thou

down as a word because it's not official I would write this down but say one thou.

And we would generally not say inches, even though it is. So we say thou a lot. One thou, two thou, 15 thou,

123 thou. I could say 123 thousandths of an inch, or 0.123

inches, but it is a lot quicker and more understandable to just say 123 thou.

in some organizations they even dropped the thou and just say 123 it's

understood that you are speaking in thousandths of an inch in my world in

dimensional calibration even a thou as small as it is is a big number and we

are often dealing with much smaller numbers so how do we speak about numbers

less than a thou? So looking back at this caliper

we see this number I'm not saying all those zeros again when seeing this

number many people would simply say half a thou

another common way of reading this number is to say five tenths where tenths

is referring to this being the ten thousandths decimal place tenths

hundredths thousandths ten thousandths or simply a tenth

this is useful slang when our base is thousands then a tenth is a ten

thousandth a tenth is very commonly spoken when using micrometers this

digital micrometer for example is reading three tenths again tens hundreds

thousands ten thousands or simply three tenths and the vernier scale on this

micrometer reads to a tenth just like the word thou we never write the word

tenth but we do say it a lot a tenth is a pretty small number and many shops that

is about a small and number as you'll be dealing with but in some cases we need

to go even smaller but before we do that let's look at the same caliper and

micrometer examples but this time in metric units this caliper reads out in

millimeters which are one thousandth of a meter one really nice thing about the

metric system are all the additional and legally official prefixes you never say

a thou of a meter just say millimeter this caliper has a resolution of 0.01

millimeters which is fine to say I suppose but I really prefer to never say

any leading zeros after the decimal points and with the metric system you

never have to when I see a number like this I imagine moving the decimal place

over three places and using the next metric prefix in this case that's 10

micrometers or 10 microns written with the metric prefix mu followed by the m for

meter when using metric units we use microns a lot we write the MU and

we say micron now officially there is no micron

it's a micrometer now the micrometer unit used to be called the micron back

before the full implementation of the metric system for all the different

units microliter microgram micrometer get it but in practice everybody says

micron but we don't write that word it is slang it's unofficial when you're

writing use the proper metric name or the units but when you are speaking

micron is what everybody says and speaking of microns and micrometers

let's look again at this micrometer a word that happens to be spelled the same

as micrometer but pronounced differently now I can't explain why we pronounced

the word micrometer and micrometer differently you've got the wrong doctor

Salsbury to help you with that question back to this micrometer the resolution

of this digital mic is 0.001 millimeters

and if I move the decimal place over three places 1 2 3 we see that .001

millimeters is 1 micron I suppose we shouldn't be too surprised that a

micrometer I'm sorry a micrometer reads to a micrometer coming back to inches as

I mentioned previously there are times when we are using numbers smaller than

tenth what do we do then I don't think you want to be saying a tenth of a tenth

let's look at the solution for these really

small numbers on this micrometer this number 0.00005 inches is the resolution

of the micrometer some people might say this value is half a tenth if this is

the ten thousandths place the five here would be half of that so half a tenth is

correct and that's a pretty good way of speaking

there are times however where it's useful to use a different units a much

smaller units the millionth of an inch if we move the decimal place over six

spots one two three four five six we get the number fifty for fifty millionths

of an inch we may say millionths

but the proper unit is borrowed from the metric system just like we have the

micron or micrometer is a millionth of a meter a millionth of an inch is a micro

inch and the notation is mu inch or mu in now not many people use millionths

every day unless you're hanging around in a dimensional calibration lab there

are some products like gage blocks ring gauges pin gauges that are specified in

millions or micro inches all the time and in surface roughness that values are

expressed in millions as well even this common micrometer if you ask me what's

the resolution I will say 50 millions or one micron so that's the language we

speak thow tenths millionths microns

micrometers micro inches terms you need to know to work in this business now you

may have noticed that I avoided any discussion about converting between inch

and metric units this was intentional however I do find

it very useful to be able to quickly convert between units but I didn't want

to get into that in this episode the Technical Bulletin I mentioned earlier

does have some good tips on conversions but for now to be complete let me state

the most important conversion in our business one inch is exactly equal to

25.4mm that value is exact with infinite precision

and as a measurement professional I don't get to say that very often thank

you I'm Jim Salsbury and I'll see you next

time from the metrology training lab