In total shock over my Shars 3-Jaw Chuck

[GrizzlyBagWorks]

I finished restoring a 1939 Clausing Lathe some time back. The original chuck had .020" runout and was totally unusable. I really wanted to put a vintage chuck on the machine but couldn't find one locally and didnt' want to risk ordering one on eBay.... So I purchased a Shars 3-Jaw with removable jaws.

It arrived this afternoon and I had an opportunity to turn/face the backplate and install the chuck. The fit was absolutely a perfect interference fit. I bolted on the chuck and tested it with a .0005" indicator. I was getting around .0025 runout, which I was happy with. When I was attaching the backplate I noticed one bolt had a little trouble going in so I took a closer look. The bolt holes on the backplate weren't lining up perfectly with the chuck and I was getting some rubbing on the head of the socket head cap screw which canted the chuck very very slightly. So I ground down the head so there wasn't any interference and reinstalled.

After that runout on the chuck body was less than .0005". I threw a few test pieces in and the results are below. I re-chucked all different material and am getting the same results over and over. I can see almost no movement on the indicator. I'm guessing .0001-.0002 runout on this. At this price I'm absolutely blown away. I was expecting the worst.

Is this normal or did I get really lucky?

 

[mikey]

Impressive! This is a good example of stacking tolerances - the accuracy of the spindle, spindle register, the accuracy of the fit of the backing plate on the spindle, the accuracy of the fit between the backing plate and the chuck, and the chuck itself - all of it will contribute in one way or another to run out. The chuck is just one of the things that gave you that result and as the scroll and jaws wear in, the accuracy will change. I am more impressed that you got your lathe spindle restored so accurately and your backing plate so precisely machined.

So, great result from a Chinese chuck - congrats! More importantly, YOU did a great job on the spindle and machining.

 

[Bob Korves]

The tip of the indicator is supposed to touch the work! Great job on setting up the chuck...

 

[darkzero]

Awesome! Couldn't have better asked for than close to that!

To answer you question, no it's not normal, just lucky. But in lucky I mean lucky that you got a good scroll & that the jaws were ground well concentrically to the register. That's not common on Chinese chucks, heck even on the quality name brand chucks, most don't guarantee under .002" TIR on plain back chucks.

Like Mikey said, the rest was a good job on your work.

 

[Ulma Doctor]

Nice Work Grizzly!!!


Stefan Gotteswinter from youtube modifies the register by taking a couple thousandths off and then indicates the work true and locks the chuck retention nuts.
he gets near 0 runout
he has a chinese 922 that he has made into an impressive machine tool

 

[darkzero]

Nice Work Grizzly!!!


Stefan Gotteswinter from youtube modifies the register by taking a couple thousandths off and then indicates the work true and locks the chuck retention nuts.
he gets near 0 runout
he has a chinese 922 that he has made into an impressive machine tool

I also did that to the stock 3-jaw that came with my lathe as well as my ER collet chuck for the lathe. Certainly not my idea of course but I call it "Tap-Tru".

Downside is that it can possible get knocked out of alignment with heavy machining. Never happened to me as I only kept my stock 3-jaw around for a beater chuck & doesn't get much use anyway. Unless you have a large lathe with gobs of power, it'll probably never happen unless you crash. But just don't crash & it's easy enough to tap back into true anyway.

 

[brino]

Is this normal or did I get really lucky?

I don't know, but either way; congratulations, well done!

-brino

 

[higgite]

Congrats Grizzly! I have to use darkzero’s “Tap-Tru” method to get anything close to .0005”.

Which leads me to a question that has been haunting me and is sort of on topic. Regarding taking a couple thousandths off the register and then tapping on the chuck to center the work, why have a register at all? I understand having an undersized register for a Set-Tru type chuck with adjusting screws that bear on the register, but for “tap tru”, what purpose does a register serve? A flat faced adapter plate sure would be easier to make. So, should I patent the heretofore unheard of flat faced chuck adapter plate or just pay better attention in class?

Tom

Note to Mods: If you think this is OT, let me know and I’ll delete it. Or you can.

 

[4GSR]

..................

Note to Mods: If you think this is OT, let me know and I’ll delete it. Or you can.

You're good..... just pay attention in class.

I have a 6" 3-jaw, bought new, mounted on a chuck adapter I made. And I did the same, turn a few thousandths off of the regerster to get the chuck running true. Haven't yet had to adjust it either and it's been in service for over 15 years too.

 

[4ssss]

Awesome! Couldn't have better asked for than close to that!

To answer you question, no it's not normal, just lucky. But in lucky I mean lucky that you got a good scroll & that the jaws were ground well concentrically to the register. That's not common on Chinese chucks, heck even on the quality name brand chucks, most don't guarantee under .002" TIR on plain back chucks.

Like Mikey said, the rest was a good job on your work.

While I tend to stay away from Shar's tooling, I did happen to buy one of their diamond wheels for my carbide grinder, and I have to say it performs better than some of the Norton wheels that I've had. I don't think luck anything to do with it, maybe Shar's quality is going up.