Hello welcome to Enots engineering I'm Alan
in this video we're looking at the three jaw chuck regrind
i did it a few years ago probably about four years ago but it does get a lot of use
i have had trouble recently in the job running true
so i measured the jaws and found that
one of the jaws was about a 0.0015"
in a different position to the other two they'd all got wear on the front of the jaws
so i thought now's the time to regrind the jaws
last time i used the ring method on the outside of the jaw
this time i'm using the bush method on the inside of the jaws
and we start off by parting the bush off and then I explain setup
so let's go into the workshop and see how we do it
i've noticed recently that my three jaw chuck
was not centering as well as it used to and i ran a dial indicator along the jaws and i found there was
over a thou taper in the jaws
more on the very end where you grip all the time
and i noticed there was some run out in the jaws as well
so i've decided it's time to re-grind the jaws
and last time i ground the jaws i use this ring
that went on the outside
opened up the jaws to grip the ring and then i could get
in and grind the jaws now with this ring method on the outside i've had
people say no you're not loading the jaws properly
it won't be as good as using the jaws to grip
i've seen people using bits of metal between the
edges of the jaws gripping on the 45 degree of the jaws
but i'm wondering how accurate those jaws are machined at 45 degree
they may not be accurate all they're there for is clearance
so that you can close the jaw because you you don't grip on the 45 degree part of the jaw
so if that's not accurate on the 45 degree machining then you could be
gripping one jaw slightly further open than the other jaw
and every time you put a piece of work in the chuck
you've already got a built-in run out
this time we're going to try a different method
i've made this bush
and the main thing that you need to do on the bush is get a reasonable finish
so your jaws can grip on this it needs to be thick enough
that you're not going to crush the bush
and it needs a shoulder on the bush
so that you can push you up to the shoulder from the back of the chuck
the other thing you need to do is make sure this shoulder is just under the diameter
of the inside of the chuck
so i can put the bush in
bring it forward
and lock the jaws on the bush
now the idea of that is that i can now with my grinding wheel grind the front half true
take the bush out
and put the bush in on the front that's been ground true
and the hole in the bush is big enough to let the grinding wheel go through
and then you can grind the back half out
so what i'll do now is set my grinding wheel up
to line the center of the rotor zip spindle
with the chuck i put a collet in gripped a piece of round bar
so if I push the bar in it won't go in slacken the chuck off
and you can see it's pushing this jaw up
that tells me my rotor zip is too high so just
lower it a bit using the tool height adjustment
it's not pushing it now so i can tighten the jaw up a little bit more
until that goes in without pushing
just pushing the jaw up
move it up on the top
it's just pushing the jaw up so it's just a little bit too high
lower it down in the tool post
tighten the jaw up a bit further
so when you can move it into the chuck and just grip the bar
you know you're on center line
take the collet off the end
that's all it was just a collet in the rotor zip with a piece of rod in
you could do it the other way hold it in the chuck
and then get this to fit in the rotor zip
like that
it doesn't matter
just check that this bush will go through even the nut will go through the bush
tighten the collet
the first thing to do is dress the wheel
if i open the chuck
this is the diamond i'm using
let's put it through the jaws of the chuck
i've just gripped the diamond in the chuck
now i'm turning it round
so that the diamond is on centre line with the wheel
now that's ready to dress the wheel
but before i do that i want to put some cloth over this to stop the dust getting everywhere
and just under here i fitted my vacuum hose
i'm hoping it'll catch suck up most of the grit
the chuck just stays still and i move the wheel backwards and forwards across the diamond
so my safety glasses to prevent any bits of grit getting in my eyes
vacuums on
there are some reasons why you dress a wheel the first reason
is to remove any material that's clogging the wheel
and give the wheel a good cutting edge and the second reason is because it was
removed from the collet it's trueing the wheel up
so it's running true and I'm not going to bounce on the workpiece
i just need to take some more off the wheel so it will go through the bush
the bush that I'm using in the chuck just goes onto the wheel
now i can set the
chuck up for grinding
and the chuck jaws are just gripping on the bush
now i'll mark the
jaw up with some felt tip pen
so i can see when it's ground
so look how that looks
now this time i'm going to grind on the back jaw here
so i'll be moving towards the back of the machine
that's because if i'm grinding on this jaw at the front
all the bits of grit and dust will come up into my face
i can't lift it up and down to grind on the top jaw so the only way i can do
it is either the front jaw or the back jaw
so i'll move the rotor zip towards the back
and then go in and out once it started to touch the jaws
i'll just turn the chuck on
turn the rotor zip on
you can see there it's just grinding on the one jaw
which is what i expected and it's not touched the end yet
you can see it's touching on the back and the first jaw
it's touched all the way along
so I just need to take a few more thou off on the other two jaws are the same
now you can see
the first jaw has gone all the way along the second jaw it's nearly to the end
so i'm just taking that's wear in the jaw
and the third jaw is the same
so i had one jaw that was slightly out to the others
I recon another thou and that should clear it up
you can see there now all the jaws clear so they've all been ground
what i need to do now is move the bush to the front
i'll set my dro to zero so i know exactly where i am
clean the dust off the bush
reset the bush to the front
push the grinding wheel through the bush
i think that's okay
let's check the run out
that's 0.0035" run out there
that's about seven inches away from the chuck
so we go about halfway it's around about a 0.001"
each division each small marker on there is a tenth
so there's ten to a thou
and then at the chuck
0.0001"
i'll try that and see how i get on with it
oh well that's it for today hope that was interesting
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