Four Jaw Chuck

[wb8mdy]

I have a problem with my four jaw chuck. The chuck is an 8" Taiwanese Grizzly.When I indicate a 1 1/8" shaft to zero at the face of chuck and move out 6" the shaft will be out +.020 and -.020. I have tried different shafts and the same problem. I numbered the jaw positions and it is always #1 and #2 that shows the problem. If I trade the two the problem is reversed. Any ideas would be appreciated

[KiddZimaHater]

It sounds like the jaws are not square, (If I'm reading correctly).
Chucking on a big ring, and boring the jaws might solve the problem.

[gr8life]

Not sure if this is the answer but I had a similar problem awhile ago. You need to use a shaft that you are sure is round & straight like a dowel pin. Try the same setup w/ another shaft.
ed

[Robin R]

If you determine that the chuck is the problem not the shaft, try moving all the jaws around while noting the various readings. You may come up with a combination that works significantly better, if so make a note of the combo that works and keep it somewhere safe.

[Machinist-Guide]

It sounds like the jaws are not square, (If I'm reading correctly).
Chucking on a big ring, and boring the jaws might solve the problem.

I agree. Before recutting your jaws run a indicator across the clamping area. If they are not sq. your indicator will show it. It will only take a few thousandth to cause a .020 runout on a six inch shaft.
You should get the same indicator reading from the front of the jaw to the back.
Donnie

[John Stevenson]

Had a batch sent to me by a Northern tool dealer in the UK with the same fault.
The slots for the jaws were milled at an angle.
I gripped one on a bar turned true in the lathe and faced the register off. this made the chuck run true bur the outside wasn't.

By the time I had it all skimmed true I had spent more time than the chuck was worth.

I was told to scrap all 10.

I made a rotating 4 jaw on a MT4 taper for the small TOS with the trued up one for myself.






One went on the welding positioner as it was, run out isn't a problem on that and the rest were given away to friends.

.

[motorworks]

"One went on the welding positioner as it was, run out isn't a problem on that and the rest were given away to friends."

So mine is in the mail?