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