Metal Lathe Chuck Question

[imagineer]

A question for folks versed in metal lathe usage.

I need to get a larger 3-jaw chuck for my little bench top metal lathe. The 2 options I’m looking at are both 6” chucks that have the same capacity. One comes with 2 sets of solid jaws, one for clamping inward and one for clamping outward. The other chuck (for $30 more) has 2-piece jaws that unbolt and are reversible.

Are 2-piece jaws a good option? Any work I do with this lathe is light duty and not ‘5 place decimal accurate’.

On the 3” - 3 jaw chuck that came with my lathe, when I accidentally open the jaws too far and they disengage from the scroll gear, it’s a royal PITA to get them back in and indexed correctly.

 

[alfadan]

My cheap 3 jaw has the two-piece jaws. It's kind of a pain cause every time you switch them, you have to meticulously clean them so chips don't get under them. I believe they also stick out further that the one-piece, levering the work further out.

 

[682bear]

The 2 piece jaws generally work very well... mine are all Buck brand chucks, so I can't speak about the quality of imported chucks.

-Bear

 

[gamescastspencer]

What lathe do you have/what swing is it? If it has a 3” chuck on it now, a 6” might be on the big side.

Personally I’d go with 2pc jaws as it allows for the use of soft jaws bored to the application if needed.

For getting a scroll chuck jaws in time, each should be numbered 1-3 (or however many jaws) and the body should be numbered as well, run them all the way out, run the scroll so the start is just at the #1 jaw, bring the jaw to the scroll so it catches, advance the scroll to #2, so on. All should be timed properly doing it that way.

 

[imagineer]

ShopFox, M1049. A 6" chuck will fit.

 

[Old Man Roger]

I’m confused about the question? My chuck will grab inside or out, and the jaws are reversible if needed? I’m admittedly no pro machinist though, so maybe I’m missing something here?

 

[txvwnut]

I’m confused about the question? My chuck will grab inside or out, and the jaws are reversible if needed? I’m admittedly no pro machinist though, so maybe I’m missing something here?

Three jaw, four jaw, scrolling or independent adjustment for each jaw? All of the scroll type chucks I've seen have had two set of jaws as they can't be reversed due to the pitch direction of the scroll plate. Independent jaws can be reversed as the thread pitch for the screw is the same either direction.

As for the OP's question of which chuck to get would be one of each. I nice three jaw scroll type chuck and a four jaw independent chuck for when you really want to dial in the work piece. Also that lathe has thread on chuck so you if you can't find a ready to fit chuck in your mounting thread you will need a back plate as well. Two piece or one piece jaws are really personal preference, all of my lathes have had one piece jaws but I sometimes think two piece would be the way to go just for the ease of changing from od clamping to id clamping or for when a set of custom fit soft jaws are needed you make a set to fit your current mount setup.

 

[Shadowdog500]

How often will you be switching the 6” chuck from an innie to an outie?

The main benefits of the 2 piece jaw is that it’s quicker to reverse them, you can buy or make soft jaws, and if you crash the lathe, the inserts may be cheaper to replace. The con is less repeatability, more runout. And less rigidity.

The main benefit of having two sets of jaws is:
Precision: Generally offer less run-out and better repeatability because there is no mating surface to introduce error.
Rigidity: Solid, one-piece construction is often more rigid for heavy cutting.
Compactness: Usually lower profile, allowing closer work to the chuck.
The drawback is that it takes a minute or so longer to swap out the two sets of jaws.

We also don’t know the two chucks you are looking at. Are they of similar quality?

 

[rsanter]

I would do the 2 piece jaws.
that will easily allow the use of soft jaws or custom jaws for doing weird stuff

 

[Old Man Roger]

Three jaw, four jaw, scrolling or independent adjustment for each jaw? All of the scroll type chucks I've seen have had two set of jaws as they can't be reversed due to the pitch direction of the scroll plate. Independent jaws can be reversed as the thread pitch for the screw is the same either direction.

As for the OP's question of which chuck to get would be one of each. I nice three jaw scroll type chuck and a four jaw independent chuck for when you really want to dial in the work piece. Also that lathe has thread on chuck so you if you can't find a ready to fit chuck in your mounting thread you will need a back plate as well. Two piece or one piece jaws are really personal preference, all of my lathes have had one piece jaws but I sometimes think two piece would be the way to go just for the ease of changing from od clamping to id clamping or for when a set of custom fit soft jaws are needed you make a set to fit your current mount setup.

Ok ya, that makes sense. Mine is an independent 4 jaw.

 

[alfadan]

This is a 2 piece jaw.

 

[RoninB4]

I need to get a larger 3-jaw chuck for my little bench top metal lathe. The 2 options I’m looking at are both 6” chucks that have the same capacity. One comes with 2 sets of solid jaws, one for clamping inward and one for clamping outward. The other chuck (for $30 more) has 2-piece jaws that unbolt and are reversible.

-Needing greater capacity is quite understandable. The only hesitation I'd have is the mass of a larger chuck. The headstock bearings may/may not handle the added mass well. In addition to the added mass of the chuck there's also the added mass of larger workpieces to consider. There's really no way to tell if longevity will be affected to any degree or not. This is where the lube system or bearing quality would be a critical factor. Having said that I'd still want to upsize the chuck if it were me even if it meant the possibility of wearing out the lathe in the process. I've got a lathe that came with (IMO) a vastly oversized chuck I only drag out when I'm forced to. It's a PITA to swap chucks but that's sometimes just part of setting up a machine. I try to use the smaller chucks or collets when possible to reduce rotating mass.

Are 2-piece jaws a good option? Any work I do with this lathe is light duty and not ‘5 place decimal accurate’.

-I've worked with large and smaller lathes that used 2 piece or 2 sets of jaws, doesn't seem to be any OEM standard. I would prefer the 2 piece jaw but now that depends upon how the removeable jaw mounts. If it's just located by the fasteners then the accuracy/runout will vary. If the jaw is captured by a slot/key method then accuracy/runout will be improved. A photo would certainly help with this. My German made lathe uses 2 sets of jaws and I have to completely remove them from the chuck to swap. It can be an annoyance to do so when changing operations but I use the opportunity to clean out the scroll so it's not without purpose when changing jaws. It's important to have the 3 jaws and the chuck marked for clocking, I'd be surprised your isn't already. If not, do yourself the favor and mark them both. You may not be doing .xxxx accuracy but when concentricity of OD-to-ID is important you'll want an independent 4 jaw. We can discuss this when you feel the need to.

On the 3” - 3 jaw chuck that came with my lathe, when I accidentally open the jaws too far and they disengage from the scroll gear, it’s a royal PITA to get them back in and indexed correctly.

-I would also be VERY mindful of jaw-to-scroll engagement when opening for larger pieces. When I'm approaching capacity for any given chuck I'll continue to expand until I find the first jaw to disengage (usually #3), I will then go in reverse so that I'm certain 2 of the jaw "teeth" are engaged in the scroll. If the jaw is only engaged with 1 tooth in the scroll there's a chance it could disengage or the "tooth" could break off (overtightening) and throw the jaw back out at speed. Even though the jaw isn't very large it has great potential for being launched into your face as you lean over the machine. I had this happen to me very early in my career, no damage to me but it was an important lesson to make certain everything is fully secured BEFORE hitting the ON switch. Even a small lathe like your can cause a life changing accident.

 

[gamescastspencer]

ShopFox, M1049. A 6" chuck will fit.

Per the manual it states 5” swing over the cross slide and saddle. With a 6” chuck you cannot move the saddle beyond the face of the chuck, probably not even past the jaws, even at a zero or small diameter grip. The issue worsens trying to grip larger stock. That would require longer stickout of tools and stock and/or extending the compound farther beyond its pivot, increasing leverage and deflection, hurting rigidity.


So can you put a 6” chuck on? Yes, but in my personal opinion, it wouldn’t be the best fit. @RoninB4 ’s thoughts and concerns are well stated.

For reference, I rounded up a 3” and a 6“ chuck:

And the 3” with a 4” six jaw:

Personally, I think a 4” chuck would be the best fit for your size of machine. JMO.