Hello and welcome to Enots engineering I'm Alan today's video will go back to
some basics. I've picked up this set of gauge blocks so what I will do is have a
look at these discuss how they used, how do you set up micrometers and basically
it's a bit back to basics. I picked this set of gauge blocks up
they cost £40 and I just thought I'd explained a bit about the gauge
blocks to people who've probably never seen them before or haven't been in
engineering very long or just starting these are our gauge blocks or slip
gauges or Joey blocks or Johanson blocks the name doesn't really matter that much
they were first made by Carl Johansen who invented this gauge block set and
they are patented on the 2nd of May in 1901 in Sweden there are different types
of gauge blocks depending on the accuracy of the set and the accuracy
needed this set if you look here it says the grade for workshop you can also get
an inspection grade and it says it's international inch obviously they're in
inches and it's got here a temperature of 68 degrees Fahrenheit and what that
means is when these are 68 degrees Fahrenheit that is a temperature to give
you the correct size now the correct size might not be what's on the the
block here but it should be related back to the calibration certificate that came
with the blocks and on that certificate you'll have the size that the block
should be and the size that the block is actually at 68 degrees Fahrenheit.
What do you do with these blocks, well you can use them for checking things like your
micrometers you digital readouts your scales on the lathe if you've got
digital readouts on the lathe that they are exactly reading what you think
they're reading these are just steel blocks hardened
and the faces are laps you can see on these they look wet they are actually
got layer of oil and I think there's some grease on that mainly to stop the
face is going rusty so you can see it's got 0.600 inch
it says matrix on there. These have here Coventry gauge and tool company and
the number here of the set I've had this top off to see if there was a calibration
certificate under there or a date or anything there's nothing on them to say
how old they are they look little used so that indicates to me that we're
either used as a setting set for setting micrometers in a workshop or checking
something but not used for everyday set of steel blocks different sizes they go
from point zero five these are all inches point one and a tenth up to nine
tenths then you've got one hundred and a thou up to nineteen there then you've
got point one point two point three by four up to point nine then you've got
one inch two inch three inch in a four inch and these two are point one protective slips.
The protective sleeps are to put on the end of your build of blocks to
reduce the wear to the set there are different sized sets you can get like a
half set and you can get set that have more blocks in than this. So this is
just a basic set Each set of blocks should have a
calibration certificate showing the tested size of each block and the error
of each block now I haven't got a certificate with these and for me it's
not worth paying to get a certificate because it would be quite expensive.
I don't need a calibration certificate because I've not had any slip
gauges up to now and this is far better accuracy than what I've had in the past.
so at least now I can check my micrometers if you look at a slip gauge
or gauge block it has on it a size these are the faces that you use. Always clean the
faces before you wring them together the way you wring them together is put them
90 degrees turn them together move them in line and that should hold.
That will stay on there showing that it's been wring correctly.
If it's a worn set or there's something wrong they won't hold together.
They're not magnetic the reason why that's holding is that the gauge blocks hold together due to the fine finish.
on the surface. Each surface is ground and
lapped perfectly flat I'll start building up the size one point five
seven four eight so you start with the smallest number first you can see from
this set at the back here it goes up 0.0001" of a thou so we'll start with
the eight tenths which is that one so we've got the eight now we want 0.004"
which is the second row these are in thous there's the four thou so we've got
the four now we want the seven which is here 0.17"
and now we should have the half inch but we don't use the half inch because we've
got point one point two point three so to get the half inch we need the point
two which is here. Point two so all those add up to
point five seven four eight and to get the inch we can just take the inch block
which gives us one point five seven four eight so we fit these together then we
have the build up see they're all stuck together that build up gives us one
point five seven four eight now if you have the calibration certificate with
your set you can check the accuracy of this stack I add in the errors together
from the calibration certificate the calibration certificate should give you
each block listed what it should read and what the deviation is from the
stated size normally the deviation with a minus from the original size is
because the blocks do wear out it's I think it would be quite rare to find a
block that was oversize so assuming that your calibration certificates gave you
this that the one point one zero zero eight at an error of - 0.00001
and the other blocks that we've used to build up this size one point
five seven four eight had these errors you can add the errors together and that
would give you an error of 0.00014" now if your accuracy needs
to be spot-on you can add these up and when you know that you're an error of a
tenth you could change your first slip gauge for the next one up providing you
know what the error is maybe the next one up has got an error of 0.1 again or
changing that for the nine you'd then only be
point zero five out but you're getting into figures now to get the accuracy
here you need to control the temperature and obviously with temperature variation
to slip gages will expand and contract and it's surprising how much they do
expend and contract just by holding them in your hand for a few seconds you'll
probably make them expand I've got the selection of micrometers here this is
the one I use mainly on the lathe this is a one to two I'll use a one inch slip
gage will just check this micrometer with the slip gauge. Now I think you might
just be able to see that this is actually reading about a
thousand more than what it should be I had no way of testing this micrometer.
I've been using it for years See how this is use a ratchet this is
actually a half a thou that size there is one and a half inches.
I don't now if you can see that on there
so considering that on hasn't been checked for about thirty years it's not
too bad. Now another problem you get with your micrometer if you using it for
lathe work all the time and you do quite a bit is that the anvil which is this
part here will wear like this so you will end up with a dip in the middle
where you're constantly measuring over round bars so what I used to do was once
a year because I'm always using it every day we would lap the faces of the
micrometer to make sure they were square and flat to take out any error we were
getting because of a worn anvil we did this with a block of I think there's a
cast iron block about half inch thick with little grooves cut into it and
you'd rip the micrometer onto it rubbie up and down and it would slowly take off
anywhere to adjust the micrometer you take your spanner which you should have
been supplied with the micrometer if you turn it over on the back you can see a
small hole where this spanner just fits into that hole and you turn the body of
the micrometer so that the datum line lines up with your zero when you've got
your slip gauges in and that's how you reset the zero this is a combination
micrometer it gives inches here on this barrel and on the back one is metric
and if you look at these turn it around that way if you look at the battle here
you can see it's got going around on a spiral the metric size so in this lines
up with that line you know you've got ten millimeter
that's a micrometer with both Imperial and metric on the only difference is that on
the Imperial one division is 0.020" not 0.025" that's made by Shardlow micrometers
of Sheffield I hope you found that interesting and we'll see you next time