Grinding the Jaws

**bouboulas** · Mar 28, 2020, 03:35 PM

Hello everybody !!
Grinding the Jaws on a 3 Jaw Chuck

**jdurand** · Mar 28, 2020, 06:46 PM

Of course they will now be accurate ONLY at that diameter since most of the error is in the spiral, not the jaws.

**Ralphxyz** · Mar 31, 2020, 06:56 PM

The indicator at the end is not the same diameter and is much improved.

**Floradawg** · Feb 28, 2022, 07:26 PM

Originally Posted by Ralphxyz

The indicator at the end is not the same diameter and is much improved.

TIR makes it look worse than it is. Very little runout afterwards. Of course you don't normally think of 3 jaw chucks as being that accurate anyway.

**G.Paul** · Apr 1, 2020, 06:07 AM

I would cover the ways of your lathe. This guy looks to me like a wanna be u-tube star

**gatz** · Apr 5, 2020, 06:12 PM

definitely cover the ways!

Get rid of the long-sleeve shirt!

Get rid of the jewelry!

**Floradawg** · Feb 28, 2022, 07:24 PM

Originally Posted by gatz

definitely cover the ways!

Get rid of the long-sleeve shirt!

Get rid of the jewelry!

And don't leave that damn key in the chuck.

**thehomeengineer** · Apr 5, 2020, 07:52 PM

I think this is a new chuck that could have been adjusted on the back plate. I have seen this so many times when a new chuck is fitted to a lathe that it doesn’t run true The chuck needs to have a bit of adjustment on the back plate or you will never get a new chuck to run true. A friend only a month back bought a new chuck for a Myford lathe and explained it was no good. I removed the chuck from the backplate re machined the back plate used a test bar and clocked the new chuck true to lathe axis. Unfortunately the chuck in the video will never be true as the reverse jaws will also run out and the jaws ground will not be able to hold anything internally as these will not be true to the lathes centre line either. Very expensive mistake I am afraid.
The Home Engineer

**gatz** · Apr 5, 2020, 08:54 PM

@thehomeengineer ,
I had thought of that too, and it looks like there are 3 (?) bolts holding the backing plate to the chuck which would have allowed adjustment.
However, the chuck body "appears" to be running true..with no discernible run-out; if it did have, it would've been vibrating.
He should have checked that first.

I don't know why he thinks TIR of .002 is sufficient.

**Floradawg** · Feb 28, 2022, 07:30 PM

Originally Posted by gatz

@thehomeengineer ,
I had thought of that too, and it looks like there are 3 (?) bolts holding the backing plate to the chuck which would have allowed adjustment.
However, the chuck body "appears" to be running true..with no discernible run-out; if it did have, it would've been vibrating.
He should have checked that first.

I don't know why he thinks TIR of .002 is sufficient.

That's a metric indicator. Each division is 0.05MM. A very small amount.