New 3 jaw chuck with massive runout

you can make a poor man's set tru by drilling the mounting holes slightly oversize
install the chuck with bolts only snugged slightly and with a gauge pin you can test the runout
after ascertaining the runout, it can be adjusted to near zero by tapping the chuck into position while spinning the chuck and observing the runout.
once the runout is minimal, lock down the chuck and move on.
 
Shars can be a pain to deal with. I bought a 4" 3-jaw and backing plate and after several hours of work I was able to meet spec at a hair over 0.003"
However, the second set of jaws was terrible and I went back and forth with them to get a good set sent out.
If all else fails, contact your credit card company and tell them you didn't get what you paid for despite what Shars says
-Mark
Next time I'll get a Pratt-Burnerd or maybe one of those Sanou chucks
 
I appreciate all the feedback. I haven't had the time yet to fiddle with the lathe since posting about the issue. I will report back when I do. Thanks!
 
wa5cab said:
Where in Houston are you located? I live on the West side of town, about a mile north of I-10 and 1/4 mile SE of the intersection of BW8 and Hammerly Blvd.

I am afraid that your only viable solution if the problem is actually the chuck is going to be to return it to Shars. Mikey is correct that you can't normally expect to get 0.000" runout with a solid-body 3-Jaw chuck. But if they advertise 0.003 Max, then 0.014" is definitely excessive. But first there are some more checks that you should make.

First, confirm that each jaw is in its correct slot. Both the slots and the jaws should be numbered from 1 to 3.

Then set up a dial indicator and measure the runout of the spindle register. While you are at it, measure the runout of the 3MT taper, although that has nothing to do with the chuck runout.

Mount a dog driver plate (often incorrectly called a drive plate) on the spindle. Mount a dead center in the spindle and a live center in the tailstock ram. Install a dog on a precision test bar and mount the bar between centers. Check its runout at three or four places and if not 0.000" rotate it relative to the spindle and adjust for minimum. Match-mark spindle or drive plate and bar. Then either video tape it or photograph it. Remove the back plate from the chuck, dismount the test bar, and mount it in the chuck. Finally, re-mount the bar and chuck between centers and indicate the register area on the rear of the chuck. Assuming that the bar has no runout and the back plate was perfectly made, you should get 0.014" runout on the chuck register. Photograph this for the record and send the chuck and the photographs all back to Shars.

I would suggest that you spend the extra bucks and buy a Buck-style chuck with 2-piece jaws.
Click to expand...
wa5cab,

I'm basically a couple of blocks away from Minutemaid stadium. Haven't had the time to mess with the lathe since posting, but I'm under the impression that the chuck is a "buck style" chuck. My chuck has 2 piece, reversible jaws. It's Shars model #202-5433.
 
Just snugging up the mounting bolts and tapping on the chuck to minimize runout is known as the “Tap-Tru” method. (A shout out to Will (Darkzero) for christening it with that moniker.) I have a “Tap-Tru” 3-jaw chuck myself, but it has nowhere near .014” runout. That’s seems like an awful lot, like others have noted. My concern with turning the spindle register down far enough to offset that much runout would be imbalance when the chuck is spun up to speed. Especially one that size. I’d talk to Grizzly about exchanging it. ymmv

Tom
 
If it is actually a "buck style" chuck, you didn't mention that earlier. After cutting and installing the threaded back plate, then you have to install a precision test bar and adjust the runout to 0.00" or as close to that as you can get.
 
Unfortunately, according to what I found on-line, it is NOT a Buck-style.
 
I appreciate all the replies and thank you so much for the information. Unfortunately, I haven't had much time to mess around with the lathe as I'm in the midst of building a motorcycle. I did however rotate the chuck around the backing plate and the run out followed the rotation.

Being a little impatient and lacking time to do more checking as instructed, I then double checked the diameter of the backing plate registration against the chuck registration and found I had about 0.0085" clearance. So I jumped the gun and shaved a bit more of the backing plate registration. A little bit of bumping around on the chuck body and I've got the run out down to 0.0035". Much better. Later, when I have more time to fiddle with it and when more precision is wanted, I'll spend more time to get it dialed in a little more. Most of what I need to do right now is just facing, boring and then putting the part on a mandrel to turn the diameter.

wa5cab, I apologize for the misunderstanding of the nomenclature. I didn't realize that you were talking about the Adjust-True Buck chucks (I think that's what they are called where it has the bolts that go up against the registration from the side of the chuck body). I was thinking that "buck style" meant 2 piece jaws which this chuck does have, but does not have the adjusting bolts.

I do need to spend some time and align everything. I did have the lathe completely apart to powder coat it and am not sure about the head stock alignment or tail stock alignment. I know I'm cutting a slight taper (around 0.001" over a 3.5-4" span). But what I need to make right now for this mc build doesn't require anything that precise.

I did unfortunately discover that the 4 jaw chuck that I bought used is pretty much toast in the over 2.5-3" diameter. I'm not real happy about that. Grrrrrr.

Thanks again!!
 
OK. If you have it down to 0.0035, you can probably get it a little better than that if needed. Good luck. And too bad about the 4-jaw.
 
First, we need a little clarification on your chuck. Is there a recess cut into the back of your chuck? If so, does your mounting plate have a matching tendon that is almost exactly the same OD as the ID of the recess? This is where you keep runout to a minimum, by having the two parts mate almost line-to-line, The screw holes do nothing to the runout - they only hold the chuck on the plate. If you chuck can wobble on your plate, that is where your problem lies.

Also, when using a 3-jaw, mount your part, then scratch around the #1 jaw on your part and mark your part. Now, when you have to unmount something for whatever reason, you can return it to nearly the exact same spot as before. You may experience a small amount of runout, but it should be minimal.
 
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