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Took apart 4 jaw independent chuck, now it's hard to turn the screws

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Pcmaker

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I have a Precision Matthews 11x27 lathe. I put in the 4 jaw independent chuck yesterday to get used to it and I noticed that there's a tiny bit more resistance when turning the screws when compared to my 3 jaw chuck. So, I took it apart. Took off the jaws and the backplate, but I numbered the jaws first so they go in the same spot when putting it back together. When unscrewing the jaws out, it became extremely hard to turn towards the end, just before them putting out, but I managed to get them out. I couldn't get the large pins that hold the screws in place out. I gave up after tapping them with a punch and hammer. All I did was spray down the screws with WD40. They turn freely and easily without the chucks on.

When I put everything back together, jaws in the same area they came out of, it was very hard to turn the entire way. It's way worse than before and it's all the jaws, not just one. There's only one way to put the jaws in, so I couldn't have messed that up. I just pushed it in and turned the screws until the threads engaged, but it was tough getting them all in.

I took the jaws apart again and looked at the scrolls. Everything is free of debris, including the threads on the jaws themselves. What gives?
 

Cadillac STS

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Could it be you need to add lubricant? Take apart and degrease, clean then put together without lube?
 

Pcmaker

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I took it apart again and lubed it up with WD40 even more and still the same issue. the heck is going on. I had sprayed off the grinding dust with WD40 and that's about all I did. I thought that would make it turn easier, not worse.
 

cbellanca

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Remove the jaws and check to be sure there no burrs on the alignment slides, on the chuck as well on the jaws and screws. Since the jaws are each independent, I would try to install them in different positions to see if they work any easier.
 

JimDawson

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You may have to do some stoning on the jaws and chuck body. Sometimes they are a bit tight. I had to do this with mine.
 

Pcmaker

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What do you call those stoning tools? And what sizes do I need to get? I've always wanted a set, but don't know what they're called so I can order a set from Amazon.
 

darkzero

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I had a similar problem with the 4-jaw that came with my PM1236. A good cleaning & stoning helped a little bit but one jaw was always tighter than the others & the others felt a bit on the sloppy side. The only thing that helped the most was swapping the jaws to different slots. Played around & found a good combination that was ok. Finally I got sick of it, sold it, & bought another chuck.
 

Cooter Brown

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Dressing stones are for cleaning up diamond and CBN Grinding wheels.... He needs to search for Norton india oil stones....

I have one like this I use it for just about everything...
And I have one like this that doesn't leave the lathe... I use it to touch up my HSS tooling....
 
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Dabbler

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A word of caution about using hand stones... - that india stones.

You don't use much pressure at all: very light pressure and Varsol as lubricant is all you need. You aren't reshaping the T slot, you are cleaning up tool marks and burrs. If you press hard, you may ruin the chuck.

If you have to take a half thou or so because the milling was done wrong, go to a coarser stone, such as a 60, then finish with a 120, then 400. BUT PLEASE DO THE FIRST PASS WITH A 320 OR 400 TO GET RID OF ANY BURRS.
- A toolmaker who had to fix a master machinist's work taught me this: investigate with the 400 grit. now you know what you have.
 

mmcmdl

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Be aware that WD 40 is not a lubricant. It's more of a solvent. Try lubricating with a something like way oil.
This is absolutely true . WD has no lubricating abilities . I always use brake cleaner when cleaning and smear some STP oil treatment on for lube . It works great when installing bearings too . :encourage:
 

Pcmaker

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I really want to get the screws out, but I can't get the retaining pins to move. It's the only thing that prevents me from fully taking down the chuck.
 

JimDawson

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Please post a picture or two of the retaining pins, front and back. Let's see if we can figure out how they are held in place.
 

Janderso

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It's an Asian Chuck, you roll the dice with those.
Sorry.
 

Pcmaker

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I let the the back of the retaining pins soak with WD40 and hopefully that'll loosen them up.

Front:



back:

 

Larry42

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Stone the burs off, check fits. If free, put the Chuck in a pan of solvent and wash well. If not free use a sharpy marker to look for where it is rubbing. Stone the tight spots, rinse & repeat. Wipe it down with some oil and don't try to use WD-40 for anything but a poor solvent or aluminum machining anti-stick.
 

Pcmaker

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I just got a reply from Precision Matthews about the retaining pins. They advised against taking these out.
 

Cadillac STS

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Why not ask them for a replacement 4 jaw if it is really binding?
 

JimDawson

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Mine had a screw next to the pin holding them in. Yours must be pressed in. Might be an interesting project to get them out without breaking them. o_O
 

Liljoebrshooter

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I took my chuck apart before. It looks like the same type. I just used a small punch on the end of the pins. They are a fork around the threaded sleeve.

Joe Hynes
 

Tozguy

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I took my chuck apart before. It looks like the same type. I just used a small punch on the end of the pins. They are a fork around the threaded sleeve.
Joe Hynes
I am with you, Jim and Joe, go for it! Anything that went together can come apart.

If you already know that the pins are resisting, I would make a custom punch, U shaped with wide flat ends to contact as much of the pin as possible. We don't want to peen the end of the pin.

From the picture it looks like the pins might already be peened a bit. If they are, use a Dremel to remove any burrs that would prevent the pin from clearing the screw.

With the custom punch, if you have a press try that first before getting out your big hammer.

There should be more satisfaction from fixing the problem than from any other approach.
 
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Cadillac

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With the jaws out I would try throwing on a press and just put enough pressure to see what happens. Fully supported of course. Pb blaster is one of the best for freeing stubborn stuff. They should be able to come out but might me tight with crude from assembly.
 

Pcmaker

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I filed down the mating surfaces until the movement was nice and smooth on all 4 jaws.

Then I put the backplate on, cam locks, etc.. and now it's hard to move again. Not as bad as before, but still hard to move. I don't know what the backplate has anything to do with it.

I'll be filing down some more, little by little until I get the desired movement.
 

WarrenP

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So, what happens if you loosen the screws on the back plate, does it make it move better? If so thats probably where the problem is. I would try it with everything loose then tighten different parts one at a time to see where the problem is.
 

Pcmaker

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I loosened up the back plate and tightened it up again and that worked. I have no clue why it did that. The bolts went from the head to the backplate and nothing else. It had nothing to do with the screws or the channels.
 

homebrewed

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It sounds like the head warped due to uneven force on it. When I tighten a bolt circle I creep up on the final torque-ing to keep the pieces as flat as possible. By now it's just a matter of course to do it that way, beginning from when I started swapping studded tires on/off my skiing car.
 

Pcmaker

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Looks like I took off a bit too much metal on one of the jaw grooves. One jaw wiggles just a tiny bit when I move it side to side. I hope it dosn't affect it too badly...
 
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