Been Noticing Something About My Chuck

[JoeLee]

What I've been noticing for about a year is it is taking more and more force to open the chuck to remove a part than I applied to close it. I have never abused this chuck and never use excessive force when closing it on any part or stock. This seems to be getting worse. The jaws are well greased and move freely throughout the range. I remove the jaws, clean the scroll and jaw teeth and apply grease on a yearly basis. I'm wondering if it needs grease on the other side, ring and pinion side.
I've only split the chuck open once and that was back in 2010 but what I found was I really didn't need to do that as it was clean and well greased inside. Nothing can get in there anyway.
I Bought the chuck back in the late 90's. I used the recommended Bison / Tool Mex high pressure grease on the inside. All three pinions act the same.
Any ideas ??

JL...............

[Mike279]

If it's bugging you enough to ask, I would say it's time to open it up and get a look.

[Toolguy]

I have 2 Bison chucks just like that one, a 6" and an 8". I don't grease mine, I run them dry. They get daily use, and show very little wear after 20 years of use. I have found that when they don't turn freely, they have chips in the scroll. When I take the jaws off and clean everything out, and put it back it's all free and easy again. Maybe the grease is holding chips in, and not allowing a good cleanup?

[JoeLee]

At first I was thinking perhaps the "0" pinion developed a slight flat spot causing it to "lock" against the scroll but I don't feel that when I tighten it down. The other pinions have the same feel when opening but not as bad as the "0" pinion.
I know what it feels like when a chip gets stuck in the scroll and locks up the jaw, but that's not the case this time.
I can remove all the jaws, clean and grease everything again but if the problem persists I'll have to go through all that again to split the chuck.

It tightens up normally through out the gripping range. It's just when I go to take the part out. It requires ten time the effort to break / release the grip. Once the jaws break loose it feels normal.


JL...........

[J Tiers]

Greasing is probably the cause. I grease the BACK and center bearing of the scroll, but never the jaws. The jaws get a bit of oil only.

It's worth taking the chuck apart every year, or earlier if it seems to be needed. There will likely be chips in places you do not expect them.

[JoeLee]

Greasing is probably the cause. I grease the BACK and center bearing of the scroll, but never the jaws. The jaws get a bit of oil only.

It's worth taking the chuck apart every year, or earlier if it seems to be needed. There will likely be chips in places you do not expect them.

This is what I'm thinking. The jaws and scroll are well greased, so the problem isn't there.
Last time I split the chuck and greased the inner workings was in 2010. I have a feeling that the grease has dried out and there is no longer coating the ring and pinion causing excessive force to break it loose under pressure. I guess that's my next project. Will have to clear some bench space for this job.

JL.............

[J Tiers]

Had chucks with dry and crackable grease.... they turned fine. odds are that it is crud in there, grease seems unlikely to jam the chuck by itself.

[Bob Engelhardt]

[snip]
The jaws are well greased and move freely throughout the range.
[snip]

[snip]
It tightens up normally through out the gripping range. ...
It requires ten time the effort to break / release the grip. Once the jaws break loose it feels normal.
....

Grease/chips don't explain this. Especially the break-the-grip part. That sounds to me like jamming. Maybe something gets cocked a little when tightened. The chuck has been used for 30 years, even if carefully, things do wear.

[kev74]

Another vote for disassembly and cleaning.

In addition to freshening things up, you'll be able to give it a through examination.

[LKeithR]

I think that most professional machinists would agree that greasing a chuck is a bad idea. While
the chuck may operate more smoothly the grease tends to hold chips, especially really fine particles,
in the working mechanism. Eventually the built up crud makes the chuck harder to turn and, of
course it's going to make for faster wear. At the very least if you want to keep grease in a chuck it
should be disassembled and cleaned more often.

And you have to understand that, like a lot of other stuff in a machine shop, a chuck will wear and
get looser over time. They are not lifetime fixtures...

[old mart]

I would take it completely to bits and degrease everything. Look closely for anything stuck on where it shouldn't be, and try out the master jaws in their respective slots for smooth movement. The screws which hold the 3 pinions in the body should not be tightened, but left loose, they cannot fall out, but can cause problems. Just screw them in underflush of the body. You could use grease on the scroll bearing and pinion teeth and pinion bearing bores, but only oil on the scroll and jaw slots. Check that there are lining up marks on the 3 parts of the body, so they go back together the same. 12 years without proper cleaning is a long time, and your chuck looks like new, I would strip one down every few months to get the swarf out, and an airline will not do.

[BCRider]

I grease mine but only with a very thin film. Like I pick up a little grease on an old toothbrush and spread it around like it costs serious cash. The hope is that it will lube the workings well but won't catch and hold too much of the swarf. And at the same time not decorating the lathe, back panel and me in a line of lube like oil will do.

It's been more years than I want to admit since I had my own chuck apart for cleaning and for sure I can feel chips in the scrolls that need to be "bumped" out of the way with some back and forth now and then. But it's never caused the tight to release issue like you're describing. I think it's time for opening it up again to get a look at what is going on.

One possible cause that occurs to me is that the inside plate that holds the scroll in position might have come loose and backed off. If so then the scroll might be wedging it self back against the pinions and causing them to feel tight for the release. That's just a shot in the dark though.

Unless it's something that has come loose and is causing the wear I can't imagine that it's worn into this failure mode. At least not unless it's seeing constant daily use in a full on working environment of a proper working shop. We HSM'ers simply don't spend long enough in the shops to even come close to making the machines work as long and hard as a full on commercial shop.

Very sweet looking Clausing you got there.

[JoeLee]

Had chucks with dry and crackable grease.... they turned fine. odds are that it is crud in there, grease seems unlikely to jam the chuck by itself.

I agree that dried caked grease wouldn't be the cause. The absence of grease is more likely. I don't see how any chips can get behind the scroll to jam the pinions. Where the chuck separates is a tight fit with ground surfaces. The scroll is almost an interference fit. I've had chips in the scroll and they have jammed up a jaw and the chuck wouldn't open past a certain point. Had to pick the chips out and then it's OK. I don't see how anything can get behind the scroll and into the pinions.

JL.............

[JoeLee]

Another vote for disassembly and cleaning.

In addition to freshening things up, you'll be able to give it a through examination.

Exactly. I just have to make some bench space so I can work on it.


JL...............

[JoeLee]

I think that most professional machinists would agree that greasing a chuck is a bad idea. While
the chuck may operate more smoothly the grease tends to hold chips, especially really fine particles,
in the working mechanism. Eventually the built up crud makes the chuck harder to turn and, of
course it's going to make for faster wear. At the very least if you want to keep grease in a chuck it
should be disassembled and cleaned more often.

And you have to understand that, like a lot of other stuff in a machine shop, a chuck will wear and
get looser over time. They are not lifetime fixtures...

The factory recommends that it be greased. I remove the jaws once a year to clean the scroll and teeth. I never let the crud build up.

JL.............