Sherline Lathe Chuck

The Sherline Lathe is a good product...but the 3 jaw chuck is it's weak point. I've had enough of Hex stock working loose and jamming up the motor/cutting tool.
It only happens with Hexagonal rods...interrupted cut and vibrations throw the jaws outwards and boom! It happens no matter how tight the jaws are.
So...has anyone made an adapter and fitted a "proper" chuck?

I don't have a Sherline lathe but I use one in a Sherline rotary table which I hold in my 5" mill vise as an expedient way to make fiddly parts vs breaking out my bigger RT. If there is what I'd call a limitation its the low height of the jaws, there just isn't much grip surface. You can buy taller jaws / soft jaws but they are not cheap & I think you have to measure your existing for them to match properly... something along those lines. If you are throwing hex parts I'd say maybe pushing it beyond its limits or the scroll has possibly become distorted if it was gronked.

I have purchased a 100mm chuck brand name Harlingen which I use for fixturing & also using their 5C backplate arbor for my SpinDexer. Its actually quite accurate & much more meaty jaws & chuck body. Also comes in 4J independent & 4J scroll. This may not d you any good if adapting to Sherline thread/spindle or whatever but just mentioning. BTW similar looking 100mm chucks on Ali & Ebay can be real garbage so its a bit of crap shoot. Which is why I mention this specific name. Anyway, check the return policy beforehand.

The stick-out and significantly higher mass of a conventional 3- (or 4-) jaw chuck is a concern. Have you tried reaching out to Sherline to see what they recommend? Perhaps the chuck is faulty?

Also, are you using the Sherline tommy bars the tighten the chuck (they’ll probably ask this also)?

Corradob said:

So...has anyone made an adapter and fitted a "proper" chuck?

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It could be possible to make the argument that proper chucks have four jaws and are not self-centring.

djc said:

It could be possible to make the argument that proper chucks have four jaws and are not self-centring.

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Other than the issue is with hex stock and a three jaw chuck, a quite common and reasonable combination. Yes, you can hold hex stock in a four jaw, as long as you don't mind clamping on two points of the hex. In this case I'm thinking ChazzC and Petertha are on the right track, never had a problem with hex stock coming loose in my Sherline three jaw chucks. Or in Bison, Rohm, Buck, or other well made chucks in wide range of sizes on a range of lathes. Unless I was just trying to get away with something iffy on a hurry up job.

The OP did not mention the material being held, which jaws are in the chuck (stock, soft), or the size of the work in question. If using one inch 4140 hex on a Sherline size machine I could see having to take very small cuts as less jaw surface will be engaged, just the jaw faces that are above the front side of the chuck in fact. Not a heck of a lot of grip. Soft stock and hard jaws can be even worse for mushing itself loose. Unlikely but over tightening the chuck in this situation could spring the jaws so the work wants to squirt out the front. Odds are the tommy bars would be bent or your fingers would tell you to stop, but I guess it's possible.

If the work has a fair bit of stick out and it is not center drilled with tailstock support in place further difficulties will arise. If the issue is occurring with 1/4 inch hex stock that is fully inserted into the chuck with only half an inch of stick out coming loose, I'd be looking at a worn chuck, damaged jaw faces, or insufficient tightening of the chuck.

A very unlikely scenario but the OP is new here at least: the work is being held on three flats and not on three points right? Not trying to be insulting, but I've seen new folks get some bad advice or misinterpret what they have been reading more than once. Being mostly self taught, I've had more than one time where I just didn't get why something was going wrong or how to use a specific new tool correctly the first time out. "Oh, that's what they meant, that picture stinks!" moments.

It could be possible to argue that all work should be held via fixturing on a face plate as well, or only in collets, or any other alternatives. but I think most folks tend to default to the ease of the three jaw unless the requirements of the stock or a need to dial in the work is part of the deal.