Help Truing Badly Worn Independent Chuck Jaws

[Inflight]

The jaws on my 4-jaw independent chuck suffer from a "bell-mouth" condition that makes securing work solidly very difficult. I am looking for suggestions on how I should correct the situation. The jaws are one-piece & reversible.

I have a tool post grinder as well as a surface grinder. I understand how to properly pre-load the jaws on a 3-jaw scroll chuck for grinding but I don't quite understand how this should be done on an independent chuck.

If possible, please post a photo or image to help me visualize the setup.

Thank you for your assistance.




Matt

 

[JimDawson]

Given that you have a surface grinder, I would use that to take out the bellmouth. Give yourself a couple of thousandths of taper towards the front of the jaw so it contacts the material first. Use the keyslot as the setup point in the grinder. Also if you have a radius dresser for your grinder, put about a 2 inch radius the wheel.

See this post also. http://www.hobby-machinist.com/threads/asian-4-jaw-chuck-adventures-re-post.33311/

 

[turnitupper]

Get yourself something round, a bearing race or a piece of tube that will fit around the outside of the jaws that will correspond roughly to the outside diameters that you normally turn on the inside jaws of the chuck. It really does'nt matter, just make there's enough room to insert whatever grinder that you have. Indicate the bore of the spindle, indicate the internal jaws of the chuck to roughly correspond to the spindle. Reverse load the jaws with whatever you think is applicble. This is where the bearing race comes into its own as it is fairly robust. Indicate and grind. PS works on a 3 jaw also
John.

 

[4GSR]

You have to load the jaws by inward pressure to grind out the bell mouth created by the slop in the jaws.

Clamping a bearing race on the OD of the jaws is putting the force in the wrong direction on the jaws. Doing this is going to make the bell mouth even worse than what you started with.

Do a little searching here on H-M and there are several good threads on restoring jaws on a 4-jaw chuck.

 

[Inflight]

Also if you have a radius dresser for your grinder, put about a 2 inch radius the wheel.

If I understand your suggestion, a 2" radius would be appropriate for holding work between 2" and 4" OD, correct?

Thanks again!
Matt

 

[JimDawson]

If I understand your suggestion, a 2" radius would be appropriate for holding work between 2" and 4" OD, correct?

Thanks again!
Matt

Yes, you could just grind them flat, but if it has a slight radius there are a few more points gripping. I just came up with the 2'' off the top of my head but that is about what you would get of you were to grind the jaws with the tool post grinder.

 

[T Bredehoft]

When I ground mine, I positioned a 1 1/2" OD washer at the back of the jaws, clamped all four jaws, then indicated the front ends to be concentric. I then ground the four jaws until they were all cleaned up, and made a few more spring passes. I eventually took the jaws out of the chuck and snag ground off where the washer had been riding.

 

[GarageGuy]

Since it's a 4 jaw independent chuck and not a scroll chuck, why wouldn't you just remove the jaws and re-surface the contact area (correcting for taper, of course) of each one on your surface grinder? No need to preload anything on an independent jaw chuck, is there? Am I missing something? Since it's not a scroll chuck, the jaws have no relationship with each other except what you adjust them to.

GG

 

[JimDawson]

Since it's a 4 jaw independent chuck and not a scroll chuck, why wouldn't you just remove the jaws and re-surface the contact area (correcting for taper, of course) of each one on your surface grinder? No need to preload anything on an independent jaw chuck, is there? Am I missing something? Since it's not a scroll chuck, the jaws have no relationship with each other except what you adjust them to.

GG

That's the way I would do it.

 

[aeroHAWK]

:+1: I'm with GarageGuy and Jim.