3 Jaw Chuck Jaw Alignment Issues

[Syn3rgy]

I have had some jaw alignment issues with the chuck that came with my HF 7x10 mini lathe from day 1, and I was hoping for an opinion on the matter from someone with more experience than myself. I noticed that no matter how carefully I chuck something it always seems to wobble. If I close the jaws all the way with nothing in them, its very easy to see that they don't all "meet in the middle". I would post a picture but I am not allowed to do that at the moment it seems. Two of the three jaws seem right, but one just doesn't seem to match. Now I have removed the chuck and jaws to verify they are in the correct position and when looking for the stamps with the numbers I noticed they are barely legible, I can only really make out a #1 on the chuck and the very bottom of the #2, the #3 is basically not even there, but the jaws where in the correct place according to what I can tell. I did try to switch the 2 & 3 just to make sure and then the jaws wont sync at all so I am 99% sure they are in the correct position. I did recently get a 4 jaw chuck from little machine shop and I am able to indicate in some drill rod to half a thousandth so I am fairly certain its just the 3 jaw chuck that's the issue. Could it be I just received a bum chuck (or set of jaws)? Can I just buy another set of jaws for this chuck or is that something that is specific to each chuck?

Thanks

 

[Ray C]

By how far off is this alignment issue?

Remove the jaws and look at the backs of them -where they engage the scroll. You'll notice that each one has a different offset. Align them in ascending order on the table. Take the chuck and rotate the pinion until you see the leading/starting edge of the scroll through one of the jaw slots. Back-up the pinion just a bit and insert the 1st jaw into the slot pressing down on the jaw while giving the pinion about 1/4 turn. Feed the next two jaws the same way. Once you've done that, you'll go from 99% sure to 100%.

I have had some jaw alignment issues with the chuck that came with my HF 7x10 mini lathe from day 1, and I was hoping for an opinion on the matter from someone with more experience than myself. I noticed that no matter how carefully I chuck something it always seems to wobble. If I close the jaws all the way with nothing in them, its very easy to see that they don't all "meet in the middle". I would post a picture but I am not allowed to do that at the moment it seems. Two of the three jaws seem right, but one just doesn't seem to match. Now I have removed the chuck and jaws to verify they are in the correct position and when looking for the stamps with the numbers I noticed they are barely legible, I can only really make out a #1 on the chuck and the very bottom of the #2, the #3 is basically not even there, but the jaws where in the correct place according to what I can tell. I did try to switch the 2 & 3 just to make sure and then the jaws wont sync at all so I am 99% sure they are in the correct position. I did recently get a 4 jaw chuck from little machine shop and I am able to indicate in some drill rod to half a thousandth so I am fairly certain its just the 3 jaw chuck that's the issue. Could it be I just received a bum chuck (or set of jaws)? Can I just buy another set of jaws for this chuck or is that something that is specific to each chuck?

Thanks

 

[Syn3rgy]

Thanks for the response and procedure. I actually did do what you said, and my 99% comment was really because I wasn't sure if I had them in the wrong place that would mean they would be way off, or just a bit like they are. I measured the gap with a feeler gauge and its about 18 thou off. I guess I can post pictures, so below you can see what I mean.

Thanks

 

[Tony Wells]

Frankly, that is either a defective chuck, or someone has mixed a jaw from another chuck of the same make into it. Out of curiosity, can you chuck the ID of a bearing race or even a whole bearing if handy and see if the "other" side of the jaws has a similar issue? If not, then theoretically, you stand a chance of correcting this with a tool post grinder. If it has issues chucking ID's as well, then it's going to be a major bit of work, and I would be on the lookout for a new chuck if it were me.

 

[Syn3rgy]

Mix up isn't possible, at least not here (only me, only one 3 jaw chuck), I guess they could have at the factory or something.

Upon closer inspection of the jaws I noticed that Jaw 3 looked a little off. As you can see from the picture it looks like it wasn't ground straight. Is this something I could realistically fix? Seems like its a might as well try scenario, probably would need to replace the chuck anyways unless someone has a better idea.

 

[Tony Wells]

That may or may not be indicative of the specific problem. The serrations are machined before HT and then grinding. They're not precision by any means, so I wouldn't go strictly by them. But then, if the other jaws seemed to be consistent in that feature, it sure could be that there is a taper in the gripping surface. How they accomplished it I couldn't say, but as I mentioned, a TPG could be used to at least greatly improve on what you have. Some people are able to rig up a die grinder and touch up their jaws. It would be worth a try, at least.

 

[Ray C]

OK, the picture clears things up... Yeah, that chuck was made on a Monday or Friday I'd say. Inspector #39 wasn't doing his/her job.

+1 on Tony's thought about checking "the other side" of the jaws to check for other geometric flaws.

You could try to fix it assuming there are no other geometry problems. If it were mine, I'd do the angled sides in a surface grinder. I can't tell if you have a circular contour in the center but that would be done with a rotary grinder. I'd measure the angle of the other jaws and replicate that onto the flawed one. Then I'd trim the "nose length" (for lack of a better term) so they all touch at the same time. Jaws are pretty hard and milling would not be the ideal method of reshaping it. It would eat coated HSS in 10 seconds and give carbide a run for it's money.

Ray

 

[iron man]

That really looks like a chuck with the jaws out of time mark each one with a felt tip marker and start in changing the slots they go into untill they all come out even mine are all numbered and if you dont put them in the right sequence in the same slot everytime you will end up with what you have. If not and it turns up just bad replace it or you can grind it. I have ground a few of them I take three pieces of key stock all the same size and insert them just shy of the three holding points you are going to grind tighten down the chuck till all three pieces of the keystock are tight. This gives the downward pressure needed for accurate grinding.

Now make a jig that will allow you to hold a dremal in your tool post pick a nice fine stone turn the chuck slow and the feed really slow till all three grind even. If the outside of the jaws need grinding you will need pressure on the outside of the jaws and grind the outside clean up the chuck and your lathe and you are done I can post some pictures of the setup if you want them. Ray

 

[Syn3rgy]

Thanks for the info everyone. After some grinding, below is as close as I could get the jaws. I am sure now I will need to grid all three as described by Iron Man in order to actually get them accurate. @ iron man, if you could post some setup pictures that would be great, I am not quite sure I understand what your doing with the keystock. I do have a dremel, and various stones and diamond bits, I will just have to come up with something to hold it.

Thanks

 

[twowheelinjim]

Harbor freight is great about accepting returns on issues like this. If you call them, they might even send you a replacement. I once purchased a bunch of tools online and a screwdriver set was missing one screw driver and one torx was deformed or not finish machined. They sent me a complete set and that was great. It's an avenue worth pursuing.