9X20 Chuck

[C-Bag]

another problem with a big chuck on a relatively small swing,
the stick out of the jaws when turning sizable work and trying to grip the od of the part.
if the jaws stick out too far, there is potential for collision with the ways

While I've had first hand experience NOW with the clearance prob, as a noob my instinct was to think there's more ridgitiy with more chuck contact and not extending the jaws too far. I see spare jaws on CL and eBay but don't know the details of what works with what. Please don't laugh as there are giant holes in my limited knowledge being a piecemeal YouTube schooled wannabe, but would it be possible to get a spare set of 4jaws and carefully cut off the lowest step of the outside grabbing jaw to give you more clearance?

 

[stioc]

All very valid points about the weight and interference. I always manually spin the chucks after mounting up the stock. Having said that my 9x20 can swing 8.75" without interference so with the 7.25" 4-jaw that came with it I have 1.5" of clearance or .75" of its jaws extending past the chuck. I don't use my 4 jaw 7.25" chuck all that much but when I've had to hold rectangle stock and such I don't ever remember having any interference issues but I sure appreciated having the capacity to hold larger stock.

As for the weight, I'll check it when I get home but I think the 4-jaws are not as heavy as the scroll 3-jaws of the same size? But it's heavier than the 4" 3-jaw. As an aside a 5" 3-jaw scroll chuck is a popular upgrade for the 9x20s.

OP, perhaps more importantly make sure the spindle thread TPI matches the chuck you buy or make sure you have the right backing plate to mount a flat back 4-jaw chuck.

 

[mikey]

... would it be possible to get a spare set of 4jaws and carefully cut off the lowest step of the outside grabbing jaw to give you more clearance?

Sure, you could do that but I wouldn't recommend it. The reason is because the chuck is designed to safely hold a work piece with a certain amount of thread engagement by the adjuster and contact between the sides of the jaws and the jaw guides. Reducing this contact may can lead to distortion of the jaws when clamping force is applied and the work piece can fly out of the chuck.

Best idea is to get a larger chuck and if you cannot do that, then get a bigger lathe or come up with an alternative way to safely clamp the work piece.

 

[f350ca]

Exactly what Mickey just said, so with that in mind why not go for the largest 4 jaw the lathe can spin. You'll hold the same work as a smaller one without the jaws sticking out.
My 16 x 80 Summit came from the factory with a 15 inch 4 jaw.

 

[Bi11Hudson]

There are several variables involved in chuck size. Particularly with a 4 jaw. I have 2 lathes, a 9x19 and a 12x36. I am fortunate that both have the same spindle thread, 1-1/2x8. The issue here is that anything I acquire must (nominally) be usable on both machines.

The 4 jaw that comes with many 9x20s looks like a face plate with woodworking jaws attached.

True, it was large enough to use on both machines, but about useless for holding serious metal work. Grizzly part number H8048. I wasn't real impressed with it. A far more useful one would be Item# H7605, for a much smaller machine. Only a 3", but at a reasonable price and much more useful. I bought a 6" 4 jaw chuck, a real metalworking chuck, that is usable on both machines. Small enough to be usable on the 9x19 yet large enough for the 12x36. But expensive, even as used.

In addition, I have a 4" and a 5" 3 Jaw and a 5" 4 jaw scroll chuck, self centering. Useful for what I use it for but not viable as a second chuck. There are some others, but for smaller work requiring absolute closure. Those are not really relevant in this discussion. Grizzly has a number of 4 jaw metal working chucks, but they also are right proud of them. I would say lay back and take your time to find one at a reasonable price that fits your machine.

The big issues to consider are "will it or can be made to" fit the machine and the maximum outside size. As in can the machine swing it? The rest of the concerns will be the monkey on your back.

Bill Hudson​

 

[savarin]

Stuck a 5" 4 jaw on my 9x20.
Fully extended the jaws do not reach the bed but can hit the cross slide on some jobs.
Dont ask me how I know.
All in all I am very pleased with the 4 jaw but would not go larger.

 

[hman]

+1 on Bill Hudson's description of the "original" 4-jaw POS.

I bought a 6 1/2" 4-jaw chuck for my 9x20, and was pretty satisfied with it. The photo below shows all the chucks I had for the lathe. The original 4-jaw is at the lower right, the new one at the upper left. Also in the picture are the original 4" 3-jaw chuck and the 6 1/4" (reversible jaw) one I bought for larger work.

I've since sold the lathe. No complaints from the new owner, with whom I'm still in contact.

 

[savarin]

I can relate to the original 4 jaw as being total crap. Mine broke, was replaced, jaws were either too loose or too tight, no happy medium.

 

[stioc]

+1 on Bill Hudson's description of the "original" 4-jaw POS.

I bought a 6 1/2" 4-jaw chuck for my 9x20, and was pretty satisfied with it. The photo below shows all the chucks I had for the lathe. The original 4-jaw is at the lower right, the new one at the upper left. Also in the picture are the original 4" 3-jaw chuck and the 6 1/4" (reversible jaw) one I bought for larger work.

I've since sold the lathe. No complaints from the new owner, with whom I'm still in contact.

View attachment 293376

hman, yep that's the 7" 4 jaw I have too, and I agree it's a cheapo chuck. What brand of 3 and 4 jaw chucks did you get? were they a direct fit on the 9x20's spindle?

Also what lathe did you upgrade to and why? I ask because I've been thinking about getting a 12x at some point in the future. Not necessarily because of the work envelope but for rigidity so I can take heavier cuts than .010-.020" (aluminum with carbide insert cutters) at a time. If the bits aren't super sharp the stock tends to gal and/or jump out of the chuck with heavier cuts.

 

[mikey]

If your lathe can't take more than 0.020" deep cuts in aluminum then you need a better tool, not a bigger lathe. My opinion, anyway.