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How to dial in a 4-jaw chuck

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MikeWi

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#1
I found this on youtube, and it's really made life easier for me. Thought some other of the new people may find it useful as well. BTW there also some truly awful examples out there as well. LOL

[video=youtube;vsIaYm7g9nA]http://www.youtube.com/watch?v=vsIaYm7g9nA[/video]
 

Analias

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#2
I like this method for adjusting a four jaw chuck. To me it's a bit more intuitive. It does require a second chuck key.

[video=youtube;2KMhx4DbyDg]http://www.youtube.com/watch?v=2KMhx4DbyDg [/video]
 

Ray C

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#3
Just want to point out that if your jaws are not square, you'll have fits getting something centered no matter what technique you use. Take a piece of known drill rod, center it with the DI placed about 2" from the jaws and after its centered, move the DI about 6" further down the shaft. If it's more than a couple thou off the jaws need a little tuning. Repeat the process a few times to make sure of how much error really exists. Something to watch for is that if the slots & grooves that the jaws ride in are sloppy and worn, don't bother filing/grinding on your jaws. Excessive wiggle in the slots/grooves is the alarm clock that says "Time for a new chuck". In my early days, I once did a weld build-up and used slot cutters to bring things back to normal. It came out pretty good (much improved) but was not worth the hassle in retrospect.


Ray
 

MikeWi

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#4
Just want to point out that if your jaws are not square, you'll have fits getting something centered no matter what technique you use.
My jaws are all perfectly straight, and perfectly out of parallel with the lathe axis! The jaws grip at the forward end but not farther back, so you can rock workpiece from side to side and watch it pivoting on the opposing jaws leading "tooth". When you look all the way to the back of the jaw, it's got a lot of clearance. Same for all four jaws or in other words any opposing pair. And yes it did give me fits before I figured it out. Swapping jaws around didn't make any difference. I did a little very light removal from the front tooth of each jaw with a sanding drum, and got a little improvement, but I'm afraid to do too much without having some sort of control. It seems the jaws are all very uniformly tipped in towards the center a little bit.

edit: forgot to add that I checked with a parallel, so I know that it's not a case of the chucked piece having a taper.
 

Ray C

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#5
That's a really annoying problem to have. When you get more inspiration, you'll probably want to touch that up. As it is now, when you tighten the jaws, it will leave a heavy bite mark with the front teeth. A piece could end-up wiggling around on you too. There are quite a few threads here about how folks have used a rotary grinder in the tool post to fix that up...

Ray


My jaws are all perfectly straight, and perfectly out of parallel with the lathe axis! The jaws grip at the forward end but not farther back, so you can rock workpiece from side to side and watch it pivoting on the opposing jaws leading "tooth". When you look all the way to the back of the jaw, it's got a lot of clearance. Same for all four jaws or in other words any opposing pair. And yes it did give me fits before I figured it out. Swapping jaws around didn't make any difference. I did a little very light removal from the front tooth of each jaw with a sanding drum, and got a little improvement, but I'm afraid to do too much without having some sort of control. It seems the jaws are all very uniformly tipped in towards the center a little bit.

edit: forgot to add that I checked with a parallel, so I know that it's not a case of the chucked piece having a taper.
 

KBeitz

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#6
I fixed 3 and 4 jaw chucks with a chunk of sacrificial drill rod and lapping compound and a rubber band.
I center a short drill rod in a chuck in the tail stock the best I can and lightly tighten the head chucks jaws
on the drill rod that's covered with valve grinding compound. I wrap the rubber band around the chucks
jaws to keep pressure on the rod at all times. Then I run the lathe at a slow speed. it does a great job.
 

MikeWi

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#7
I cured mine not long after that post using a grinder. Jaws are nice and straight now.
 

RJSakowski

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#8
My jaws are all perfectly straight, and perfectly out of parallel with the lathe axis! The jaws grip at the forward end but not farther back, so you can rock workpiece from side to side and watch it pivoting on the opposing jaws leading "tooth". When you look all the way to the back of the jaw, it's got a lot of clearance. Same for all four jaws or in other words any opposing pair. And yes it did give me fits before I figured it out. Swapping jaws around didn't make any difference. I did a little very light removal from the front tooth of each jaw with a sanding drum, and got a little improvement, but I'm afraid to do too much without having some sort of control. It seems the jaws are all very uniformly tipped in towards the center a little bit.

edit: forgot to add that I checked with a parallel, so I know that it's not a case of the chucked piece having a taper.
The OEM four jaw for my 602had the same problem. I reground my jaws which solved the problem.
https://www.hobby-machinist.com/threads/grinding-my-jaws.50747/
 
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