in this video i'm going to drill out a grub screw to avoid any confusion here are some pictures of
grub screws in use there are quite literally thousands of grub screws in the two chemical
plants where i used to work in some countries they might not call these grub screws they might call
them something else but in the uk we call these grub screws this is a large motor with a pulley
attached to the end this uses a taper brush to hold the pulley in position which uses grub screws
to hold it in position this spider or jaw coupling is also held in position using taper bushes and
grub screws these flange bearings are held in position using two grub screws every single one of
these wheels is held in position using taper lock bushes and grub screws i have to say that i have
never had to drill out any grub screw on any taper bush but i'm just showing examples of where they
are used in industry this is a stainless steel shaft which is from a machine that is in a wet
environment all of the bearings are held in position using grub screws as are the helical
gears i have had to drill out grub screws on machines like this in order to remove the bearings
or the helical gears i have also had to drill out stainless steel grub screws in specialist
glass washing machines these grub screws often get stripped, meaning that the allen key will no
longer undo the grub screw when this happens the only thing he can do is drill it out in situation
for all the people that have commented on previous videos saying it's easy on the bench try doing it
in situ where there is no room and you are lead down on your front in a hot and noisy environment
well i have done that but today i'm going to drill the grub screw out on the bench
so this is the pillow block bearing that's the grub screw this is a stainless steel shaft
obviously we had to cut the shaft to get this out of the machine because we couldn't undo
the grub screw so we've got one grub screw there which i think we can undo
that one's come undone easily
i'll actually just remove the grub screw then you can take a look at it
you can see that grub screws like this tend to have like a serrated
edge on the end so that it grips the shaft so that's it it's only a very small grub screw
to drill out the grub screw i'm going to use two different sized Cobalt drill bits you have
virtually no chance of using a standard HSS drill bit on the hard materials like this it really does
struggle so if you take a look inside of the grub screw you'll see that it's got flat edges on there
and what tends to happen is when you try to drill that out with the correct sized drill bit
like that it actually takes the flats off the drill bit almost immediately
what i like to do is use a larger drill bit first and that's going to drill out part of
the grub screw and it will also drill the stainless steel part of the bearing too
so what i'm going to do in this example is i'm going to drill as far as i can
using this larger drill bit because the larger drill bit like that is also stronger so there's
less chance of it breaking and once i get so far i'm going to swap that over
and i'll continue to drill the remainder of the grub screw out using the smaller drill
bit which i think is about 4.5 mil if you take a look at the end of the grub screw
we only need to get that serrated bit off as soon as you drill off that serrated bit the grub screw
will release it will no longer hold the shaft and we'll be able to get the bearing off i'll just try
this one and now as you can see that is completely rounded off just nowhere we're going to be able to
grip that to remove it you can actually try to get these out using a small screw extractor but
because these are very shallow there's virtually no chance at all of that working so the only
option in most cases like this is to drill them out you will notice that on the bearing housing
there is actually an indentation in the top layer and that enables you to get your Allen
key or your hex key in to tighten or loosen the two grub screws unfortunately my better drill is
in the back of the van because i'm on a large job at the minute so i'm just going to use this small
12-volt drill that i have lying around the workshop so we're going to put that onto
a slow speed and obviously we're going to put a pair of safety glasses on obviously we don't
want to damage the drill bit so we're going to use some cutting paste so i'm simply going to dip the
end of the drill bit into the cutting paste i always find that when you're drilling out a grub
screw it's actually better if you can have the drill rotating before you touch the grub screw
and you can hear that that is quite tough we're actually trying to drill through the
steel and the stainless steel there at the same time so it is quite difficult
so i'm just going to clean the end of the drill bit and put some more paste on
you'll notice that the bits are coming off in very small
pieces that's because the steel is very tough if that was mild steel you'd get long spiral
pieces coming off but because it's so tough it only comes off in very small pieces like that
what you have to be careful of is work hardening the stainless
so i've now got through so far i'm now going to remove the
large drill bit and i'm going to continue with the smaller drill bit
you'll notice that i'm going at a very slow speed
again i'll just clean the swarf off from the end of
the drill bit and put some more cutting paste on
it is important when you're doing something like this that you don't try and rush it
it is important to take your time because the last thing you want to do is break a drill bit
especially a cobalt one
obviously if you are lead on your front and you're trying to do this
in a machine it's a lot harder than this this can be a very difficult job to do
i'm just going to give that a clean up so that's what it looks like in the actual hole where the
grub screw is and you can see that we've almost got it out there's only a little bit left in that
we need to get out now you should be able to see that it's actually taken the edge
off the drill bit so it's no longer cutting as it should do now you can re-grind these on a grinder
if you've got the skill to do that
but i prefer just giving it a slight file using a diamond tipped file that will often
sharpen it enough so that you can continue drilling i've just stood the drill bit up in
the vice and now i've got a diamond tipped file and these are quite literally about eight to ten
pounds they are absolutely brilliant they will file anything that is tough so all i need to do
with that is look at the edge i'm not trying to change the angle of the cutting edge or anything
i'm simply going to give it a couple of files in a forward direction to re-sharpen the bit
and just by doing that, that'll actually make the drill bit start cutting again and
we'll be able to drill out the grub screw so again i've got the cutting paste on the end
ah
actually got the grub screw drilled through there and we're actually dimpling the stainless
steel shaft you can see in there that we've actually started to drill the shaft the hard
grub screw is no longer there we've just got a few threads that are left i'm just
going to use a piece of steel and the hammer get that behind the bearing and just tap that
we've just got a bit of a burr on the end of the shaft let's give that a tap
so we can simply take the insert out of there and get a new bearing insert and we can reuse the
pillow block i know it's a bit rusty but it's still perfectly okay just a bit of surface
rust so a cobalt drill bit like that will work on
most grub screws if you work harden it you're really going to struggle and you
will probably have to use a solid carbide bit in order to drill out the grub screw
you