Truing Chuck Jaws

cuetrip said:

Been watching this guy's videos and seeing some pretty cool stuff. I'm pretty new at this and by no means a machinist. I think my MidAmerica lathe has quite a bit of runout at the chuck.

Has anyone tried this? Are there other/better/easier ways?

https://www.youtube.com/watch?v=M0RUoEswy38

Thanks,

Rob

Click to expand...

Yessir this is a standard procedure. One thing to note is that these chucks just wear out over time and can't be trued up. I buy a new chuck from Todd about once a year or so and use a washer like in the video.

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I use a 4-jaw as my rear chuck.
I find them more accurate .
And much easier to index-indicate .

Thanks for sharing! I learned several things on this video.


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Not sure if he did this in the video just started watching it but one thing that helped after I replaced the jaws on mine is there's a hole in the center of the jaws where I put a pin in. I think it's a 4mm pin I put in that I got at my local hardware store.

I have pretty good luck with the 4 jaw independent large bore chuck that Neil machined for me, I can get as close as the time I want to spend. Those who complain about the wrench in the chuck, it was removed before put to work.

Using a pair of chuck keys, makes it very quick to dial in any 4 jaw chuck. Especially if the runout is within the range of the DTI. You can get most things dialed in with about 4 goes at adjusting the pairs of jaws. 1st is to approx 1/2 of 1 pair of jaws. The 2nd is to approx 1/2 of the other pair. Then fine adjust the 1st pair, check fine adjust the 2nd pair. In like around 40 to 90 seconds the job is dialed in. Sometimes you can get it faster with a pair of DTI's to show the error of the set that is to be adjusted or at the end away from the chuck monitoring the end runout or swash.
Neil

I fought these chucks for 2 years to get them to spin a dead center true..... swore a lot and tried a lot of different things , even called Chris Hightower...........,until I found out how to use them............

First of all...... The work piece does not need to run dead nuts true....... I know some people prefess how they work within a few tenths and how true their cues are........... The truth is if you can get a tip, a ferrule, or any part of a cue within about 1 or 2 thousands of an inch everything will be perfect.


Just a couple hints..... first one pin hole used to tighten the chuck will center better than the other 2. Put a ground pin in the chuck and indicate it, Loosen and tighten it a few times and spin it and watch the dial indicator each time to see how true it is. Do this with the other 2 holes and you will see that one hole is best. I put a ***** punch mark by this hole and usually use this one to tighten the jaws.

The other hint is that those little collets for shafts never worked for me. They never centered right. I wrap the shaft or the butt with a piece of .020 plastic shim stock. The piece of shim stock is about 1 inch by 3 inch. Just wrap it around the shaft with the ends sticking out between 2 jaws. Langley Custom Cues sells a set of these and are worth every penny... I have used mine for 2 years on every shaft and they still are in good shape. They never mark the shaft or the finish on the butt.

Put the shaft in the chuck with the shim stock wrapped around it and indicate it. Loosen and spin it 1/3 turn and try again......until you get it within 1 thou run out............... I do this and I never have to shim any shaft or butt........ there have been a few exceptions that were crooken as a pretzel or not round.

You could also try cleaning and lubing the chuck..... you might need that silly 1 inch spindle wrench from Taig to remove it from the spindle. I bought one about $6. Fully close the jaws and them remove the chuck. Put it face down and remove the snap ring.... remove the scroll back plate.... leave the jaws where they are...clean it and lube it with white lithium grease..... put it back together and put it back on......................... takes about 10 min. If you remove the jaws, remember they must go back in the chuck in the proper order.

There are some that feel that you need to bore the jaws to true them up. Things do not run true because the jaws are not true, they run out because of the way the jaws clamp down on them. I have bored the jaws twice in 4 years and I don't think they needed it either time .......... I find that lightly sanding the jaws helps if there are chips, dirt, or burrs on them. Open the jaws but not all the way...... wrap your finger with 220 and sand each jaw in and out a few times to polish them..... it helps a little. if you feel that you must bore the jaws, clamp a large washer behind the jaws and just bore them to clean them up. Don't take off too much material. I haven't bored mine in 5 years and they work just fine.

One last thing I learned from a talented machinist, If you are trying to bring in the runout the last thou.... sometimes you can give the high jaw a tap from a small rubber hammer or a block of wood to get it to run true.... try it...it works....

Just like the fellow in the video... I would recommend that before you do anything to the jaws, that you accurately measure the runout that your chuck currently has. If you do not have a way to measure the the runout you are running completely blind. In order to accurately measure the TIR you need a piece of precision ground steel rod (I usually use 1/2 inch diameter x 3 inch) a dial indicator and a way to mount it. I do not necessarily agree with everything that is in the video, but the basics are fairly good.

Funny, when i got on here last year i posted a couple times mentioning 4J chucks which i use outboard, and sometimes inboard. Mostly got comments about how much time i was probably wasting.

As far as grinding jaws on a 3J, the guy who mentioned finding the nominating pinion is spot on. After that, on a worn chuck, grinding (or boring top jaws) will work in one aproximate opening. Seldom the same thoughout the scroll range it there are a lot of hours on the chuck.

For cue work, i'd just use top jaws and bore occasionally.

But i prefer (& use) high end adjus-tru style chucks on the front. Only one pinion, so no mix up. Then adjust the run out with the adjus-tru screws around the rim, if/when needed for a given job. More or less a scroll chuck that can be adjusted/centered like a 4J when needed.

If you make your own backplates, most 3J's can be converted to adjus-tru feature. But if it is a cheap import, the scroll will never repeat because they are built too sloppy internally. (Usually good machining/grinding, but too loose a fit, & not take-up provision). So converting a cheap 3J might or might not yield faster routine set up than a 4J.

smt