Hello, I’m Jim Salsbury with Mitutoyo America Corporation and welcome to the
Metrology Training Lab. in this episode we want to discuss the truly amazing
gauge block and talked about their use and a little bit about their calibration
I have to admit I'm a bit awestruck with the gauge block these simple little
blocks are something special each one with their flat and parallel surfaces
and with an accuracy of just a few millionths of an inch we've used gauge
blocks in previous episodes of the metrology training lab but in this
episode we get to understand them better and appreciate their role as a premier
measurement standard gauge blocks come in sets like these and you can use these
sets to build any length you need and when done properly those lengths are
more accurate than pretty much anything else what's even more amazing is that
gauge blocks were invented over 100 years ago and they haven't changed much
in that time they have quietly played an important role supporting all the
incredible technologies that have been developed since the early 1900s that's
pretty cool gauge blocks were invented in Sweden by CEO Hansen he didn't invent
the idea of length standards but he patented the idea of a set of blocks
that can be used to build various lengths and he was an incredible
machinist and his company was able to produce
gauge blocks the tight tolerances that allowed so many others to achieve new
levels of accuracy in manufacturing some people will refer to gauge blocks as Joe
blocks in reference to Johansson who Henson was also a pioneer in precision
engineering and the standard reference temperature of
sixty-eight degrees Fahrenheit or 20 degrees C comes in part because he
needed everybody to pick a common temperature and when the top scientists
around the world asked he recommended 68 degrees Fahrenheit because that worked
well for him we have here an actual set of Johansson blocks that one of my
colleagues at Mid South America collected you can see that your Hansen
name and Sweden marked on the gauge blocks the sets we sell today don't look
much different modern gauge block sets basically follow his 100 year old patent
during World War 1 the US government became worried about the supply of gauge
blocks to the United States from Sweden along came a mr. W E Hulk who developed
his own way to make gates blocks around 1917 he made them round with a hole in
the middle to make them easier for him to lap flat the square gauge block with
the hole in the middle was derived from hoax design and still today you can buy
Gaye's blocks in either yo Hansen's rectangular design or in hoax square
design where tangler blocks are much more common but some people like the
square blocks in other episodes of the metrology training lab you will see us
picking either rectangular or square blocks for various tasks for the
interested viewer metoya has published a little book on the history of gauge
blocks you can download that for free from our on-demand educational resources
on our website modern gauge blocks come rectangular or
square in inch or millimeter sizes the typical set includes lengths up to four
inches but you can get long block sets up to 20 inches and you can
special-order gauge blocks up to 40 inches or
one meter long the most common material for gays blocks is steel mostly because
the price is quite attractive other standard materials include carbide and
ceramics one of the big advantages of ceramic gauge blocks is that they don't
rust however if you take care of steel blocks such as wearing gloves when you
handle them and putting light oil on them when they're stored they can last
years even decades depending on how you're using them for this episode
however I'm gonna mostly use ceramic blocks the real reason is that these
lights here are quite hot and my hands sweat in these gloves and getting sweat
all over steel gaze blocks is not good practice now I can tell you some more
advantages of ceramic gauge blocks but I don't want to sound like a salesman and
that's not the purpose of this episode gauge blocks are sold by grades the
grades to find tolerances for the flatness and parallelism of the faces as
well as the tolerance for the size that's marked on the blocks the grades
apply whether the blocks are ceramic or steel and whether they're rectangular or
square for example these three 1-inch gaze blocks if they're all grade 0
according to the tolerances of the standard it would be plus or minus 6
millionths of an inch if this gates block or all three is gaze blocks have
been properly calibrated and found to be in tolerance then I would know that the
length is somewhere between the minus 6 millions and the plus 6 millionths of an
inch I told you these things were accurate if this was instead say a grade
a s2 gates block the tolerance should go from 6 millionths of an inch
up to 24 millionths of an inch days block grades are defined in national and
international standards in the US we use the American national standard for guage
blocks asme be eighty nine point one point nine you can also find the
tolerance table in the mid-to Toria catalog all manufacturers of gauge
blocks sell them in grades in accordance to the standards you should select gaze
blocks based on your accuracy needs in a calibration lab grade zero gaze blocks
are quite common so that's a brief introduction to gaze blocks how do we
use them gauge block faces are very flat and very smooth the reason for this is
that that allows gauge blocks to ring together without using any adhesive
gauge blocks can be brought together and the flat smooth surfaces will adhere to
each other without causing any damage
when done properly the gap between the two gaze blocks is somewhere around one
millionth of an inch and when you're done they can be broken apart and reused
over and over and any flat or smooth surface will ring together steel to
steel ceramic to ceramic even an optical flat such as sown here I've rung
together three different gauge blocks rectangular steel ceramic and an optical
flat all froze blocks are rung together nice and tight that's pretty needs
the idea behind yo Hanson's original patent was the particular sizes in a set
of gauge blocks they allow you to build an accurate stack of gauge blocks to
create any length you need so let's walk through the ringing process when you
ring blocks you apply quite a bit of force to avoid scratching your blocks
it's important they are clean it's important particularly for steel blocks
to also make sure there is no raised edge or burr or some sort of ding first
I'll use some des natured alcohol to clean the block and then I'll use this
millet or Sarah stone to remove any burrs this is sometimes called
conditioning the block we're not changing the length of the block we're
just removing any high spots
particularly on the edges I can use a small Sarah stone like this using a
push-pull technique or it can use a large one like this and some people like
to go in a figure 8 pattern and no you don't have to buy a midotaur Sarah stone
but they do work well some people recommend using a small grant surface
plate and it's hard to say how often you need to condition your blocks it really
depends on how you're using them if you were to very lightly slide a gauge block
across a surface plate you may feel a touch or hear kind of a scratchy sound
that indicates a raised spots in those cases you should do the conditioning I'm
also not going to pretend to understand the physics on why ringing works I'm an
engineer I just need to know that it works and how to do it in fact it seems
to be a bit debated as to why it really works we'll leave that for the
interested viewer what is it important to know
is that ringing works best with a very very slight amount of light oil or
grease on the gauge block faces we really don't use anything special in our
lab for ringing we have these 20 year old stamp pads lying around that have
some wd-40 sprayed on them yes wd-40 I can only imagine the
comments that will be posted on our use of wd-40 all you need to do is dab the
gauge block in it and then wipe it off on a dry cloth
we don't use any solvent here because we don't want to remove the oil we want
just a little bit left on it now I'm gonna bring these two blocks together
and you do have to apply quite a bit of force when you're sliding one block
against the other so I'm gonna set these two up here and I'm going to try to
slide this block against this block so this is the kind of slide technique
another technique is kind of that the push and slide technique where you come
from a side and go like this and then you rotate the block as you're pushing
I'm not doing it now I'm just trying to demonstrate how it's done
on the square blocks you can typically use a push and twist technique in fact
it looks like I just accidentally wrung those two together alright so back to
these two blocks here I'm going to push on this while I'm sliding across here
and you can see my thumb turn a little bit white as I do that and if I did it
right those two blocks are now long to burn together pretty well when you're
all done using the wrong gauge blocks you can just slide them back apart like
this if you leave the blocks wrung together for say several days or more it
can become very hard to take them apart so don't leave them
for too long ringing requires handling the gauge blocks which may warm them up
a bit so once they're wrong you can clean the outside surfaces and then let
them sit for a little while to cool back to the ambient temperature how long thus
it depends on how much you handle them and what your accuracy needs are if you
want to see how well you can ring a fun and easy test is to ring two blocks
together that add up to the value of a third say this 450 and 550 block which
add up to one inch and we compare it to a one inch block so we ring these two
blocks together and then using something like a high accuracy detector like this
Mu-Checker, I can then compare the run block stack to the single block now this
test is not super accurate but it should be good enough to see if you're ringing
skills are good enough to say calibrate a micrometer our last topic on gaze
blocks is their calibration in our calibration lab here at Mitutoyo America
we use really cool automated gates block comparators but we have a manual version
here in the metrology training lab so let's head over there and I'll discuss
some important topics on calibration these blocks are usually calibrated
using a comparison method this is the master block and this is the customer
block to be calibrated we set the comparator using the master block
and then measure the customer block in accordance to be eighty-nine point one
point nine the length tolerance for gays blocks applies across the entire surface
of the gauge block not just at that gauge point and that a standard
discusses the importance of checking the size in a dish to the gauge point at all
four corners this fixture here moves the gaze block around such that we can
measure the four corners quickly and easily in order to state conformance to
grade in accordance to the ASME B89.1.9 standard all
five of these points must be in tolerance gage block calibration practice
in the United States is sometimes a bit sloppy to save calibration costs some
people have been convinced to go with a single point calibration where the
corners are not checked at all the only time that's acceptable is when you're
only using the gage block at that exact measurement points and I think that's
pretty rare please be careful with exposing yourself to calibration risks
just to save a few dollars if you just need a cert to show some auditor well
that's your business but if you really care about quality to the calibration
right I hope you learned a few things about gauge blocks if you have questions
or want to see something else on gauge blocks please post your comments. Thank
you, I’m Jim Salsbury, and I’ll see you next
time from the Metrology Training Lab.