I have a 6 jaw Buck Chuck that has developed a slightly loose jaw. The #1 jaw still tightens as the rest of the jaws, but when indicating a part in I noticed it wiggle when it should have been under tension as the other 5 jaws were. I have taken the chuck apart, cleaned it, looked for anything that might prevent the jaw from sliding in the scroll evenly and found nothing. The bolts are all tight. Unless the guide riding in the scroll has worn more than the rest, I am scratching my head (did not measure them when I had it apart like I should have) as to what might allow just this one jaw to be a little loose.
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6 Jaw chuck with 1 slightly loose jaw
- Thread starter dwebster
- Start date
- Replies 19
- Views 610
Doozer
Titanium
- Joined
- Jul 23, 2001
- Location
- Buffalo NY
Clock the jaws around so the numbers are still in order
but they do not line up with the numbers in the body.
This is to deturmine if the problem is the jaw or the slot.
-D
but they do not line up with the numbers in the body.
This is to deturmine if the problem is the jaw or the slot.
-D
eKretz
Diamond; Mod Squad
- Joined
- Mar 27, 2005
- Location
- Northwest Indiana, USA
What were you chucking on? Are you certain it was round? In addition to Doozer's suggestion, try chucking on some items larger and smaller in diameter that are measured and checked for roundness, see if the same jaw is still loose. If so, check it and the others for any visible damage. Also remove the jaws and visually check the scroll and jaw teeth for any damage. Thoroughly cleaning the scroll and jaw teeth would be a good first step too.
I had thought about that so I grabbed some 3/4" precision ground (1045) shafting stock and it did the same. When I took it apart after I noticed the loose jaw, I completely degreased, scrubbed, cleaned and lubed it before I put it back together. I made sure all jaws closed on 1", 1/2" and some 2 1/4" stock evenly. This is a chuck from 1995 and it had a different owner before me, so I know it may not have been taken care of like I try to do. If its the slot, what to do? Weld up the loose spot on the slot and re cut the slot back to spec? I can either buy a new set of jaws so they are all wearing at the same rate or try to fix/make a replacement jaw.
eKretz
Diamond; Mod Squad
- Joined
- Mar 27, 2005
- Location
- Northwest Indiana, USA
First thing: don't get ahead of yourself. Figure out what's wrong first. Do all the jaws have close to equal backlash on the scroll when there's nothing in the chuck? It may be that you just need a jaw regrind.
4GSR
Diamond
- Joined
- Jan 25, 2005
- Location
- Victoria, Texas, USA
30 plus year old chuck. Time for a new replacement. IMO.
eKretz
Diamond; Mod Squad
- Joined
- Mar 27, 2005
- Location
- Northwest Indiana, USA
Matter of budget, I guess. Might be at home in the garage.
guythatbrews
Stainless
- Joined
- Dec 14, 2017
- Location
- MO, USA
If it's the slot it oughta be pretty obvious just shaking the master jaws. Or somebody may have boogered a jaw up. Who knows what went before.
4GSR
Diamond
- Joined
- Jan 25, 2005
- Location
- Victoria, Texas, USA
Not trying to take cheap shots at the poster, I myself has owned a few lathe chucks over the years. Mine only see light duty use now days. I recall most of the old ones I had to use had wobbly sloppy jaws on them. None of them would repeat. If you were lucky , maybe within .005" TIR on the 3-jaw chucks. Slowly as newer ones surfaced I've replaced most if not all of the worn ones with ones that are not so worn or new right out of the package. Never was rich enough to own a 6-jaw chuck until now. The two I have I don't use them that much. For me, they only have a limited amount holding range for my needs. But that's okay, I have them if I need them.
eKretz
Diamond; Mod Squad
- Joined
- Mar 27, 2005
- Location
- Northwest Indiana, USA
One good hit can make a jaw wonky. But if the whole thing is sloppy I'm with you.
So, it looks like its the jaw. The rear face of the outer jaw tooth has worn/is uneven enough on the #1 jaw that it does not fully engage with the scroll under tension and allows it to move slightly. The other jaws ride the scroll groove face in full contact. I suspect the jaw was dropped at some point and the resulting burr was stoned off a little too far. Overall, this chuck is in great shape for its age except for this one issue.
And yes, I am a small shop, so $2k for a brand-new chuck is not something I can readily justify. Most of my tooling has been passed down to me from my Dad/Uncle/Grandfather who were all Instrument Makers/R&D Machinists and were the only ones to operate my machines since they were factory new, so they were very well taken care of and never abused by some overzealous apprentice. This chuck, however, was purchased used and now I suspect why it was sold. However, I think it can be repaired and used. It has worked well prior to me noticing the slight wiggle but now I know it's there and my OCD wants it fixed.
And yes, I am a small shop, so $2k for a brand-new chuck is not something I can readily justify. Most of my tooling has been passed down to me from my Dad/Uncle/Grandfather who were all Instrument Makers/R&D Machinists and were the only ones to operate my machines since they were factory new, so they were very well taken care of and never abused by some overzealous apprentice. This chuck, however, was purchased used and now I suspect why it was sold. However, I think it can be repaired and used. It has worked well prior to me noticing the slight wiggle but now I know it's there and my OCD wants it fixed.
eKretz
Diamond; Mod Squad
- Joined
- Mar 27, 2005
- Location
- Northwest Indiana, USA
Got some photos? Not sure I fully understand what you're describing. It sounds like you're saying the jaw (are these 2-piece jaws?) is damaged where it engages the scroll? Might be able to buy a new jaw somewhere and then just regrind all the jaws together.
Sorry, no pictures at the moment. I should clarify, its the master Jaw I am speaking about. The only thing I can identify as being possibly damaged is the last (outside?) tooth of the #1 master jaw, looks like it was dropped on one side and then stoned smooth and it does not appear to bear evenly or appears to be wearing unevenly. I moved the jaws around one slot off like you suggested and it did the same thing. Outside of that, I have not had time to take it completely apart again and measure everything. Every other jaw stays tight when holding a piece of stock, like it should. So, my bet is the jaw was damaged at some point.
eKretz
Diamond; Mod Squad
- Joined
- Mar 27, 2005
- Location
- Northwest Indiana, USA
Sounds like it. See about getting a new master jaw. Might have to buy 6. Then you'll need to grind or bore the lot in place, with the jaws preloaded.
Froneck
Titanium
- Joined
- Dec 4, 2010
- Location
- McClure, PA 17059
Problem with 6 jaw chucks is 2 jaws are 180° apart so that when 2 jaws hit a high spot the other jaws stop. Also lots of "precision" ground shafting in done on center-less grinder. It's not but putting a micrometer on it it looked as if round to size.Using a Starrett 483 or 485 Vee angle mic. will measure the out of round, indicator and vee block works too!
I have set-true type 6 jaw chucks as well as all other types except 4 jaw universal. I use "soft" jaws I made from tool steel and re-cut them from time to time.
I have set-true type 6 jaw chucks as well as all other types except 4 jaw universal. I use "soft" jaws I made from tool steel and re-cut them from time to time.
eKretz
Diamond; Mod Squad
- Joined
- Mar 27, 2005
- Location
- Northwest Indiana, USA
Yes it's important to grind the jaws true under preload - I used to do this periodically every few years in a busy shop. Makes a big difference to rigidity, and if you do it regularly you don't need to remove a whole lot.
I couldn't say on the damage in this particular case without seeing it...
I couldn't say on the damage in this particular case without seeing it...
