Lathe chuck size

[skipd1]

I have a recent acquisition of a 1938 Hendey 12x30 gearhead lathe and I want to correctly size the chuck and quick change tool post for it. This machine is an RS or raised swing model and its maximum swing is 14 1/2 inches. The original purchase invoice in 1938 showed it shipped with a 10 inch 3 jaw chuck. The person I purchased it from included a new 8" 3 jaw and I am wondering if the 10 inch would be a better choice. I also assume a 10 inch 4 jaw would also work? I also assume that a CXA tool post size is okay as well?

Skipd1

[J Tiers]

Bigger chucks hold bigger work.

What do you need?

Some say bigger chucks are useless, or at least a "problem", because the jaws will stick out beyond the OD and maybe hit the ways..... I don't necessarily agree. First, that's a "maybe", and second, why not use the outside holding jaws?

[mattthemuppet]

Chuck diameter of 2/3 lathe swing seems like a good rule of thumb, so 8" chuck on a 12" lathe. As long as there's enough room for the jaws to extend you're good. The only downsides I can think of for upsizing the chuck when you get to the sizes you're talking about are the weight and the fact that above a certain size chucks will have a minimum diameter they can grip.

[Mcgyver]

8 or 10. 8" is easier to lift. I've got 10" chucks on my 13x42 and, imo, they look right. Also have a 12, but its a bear to lift so rarely use it

[Rich Carlstedt]

10 inch four jaw sounds OK but the CXA sounds too big- I think a 12" Lathe calls for a BXA

I have a 8"- 4 jaw on my Atlas-Clausing 12 " 6300 lathe and it seems big enough for my work
I think a Hendey is husky enough to handle a 10 ..but what work do you want ?
A 10-11 "Face plate is nice however
Rich

[mikey553]

My 12 x 36 lathe came with 6" 3-jaw and 8" 4-jaw. Later I have added 8" 3-jaw chuck and a 5C collet chuck. If you ask me which chuck I use the most, it would be the 6" one. It is accurate, light and easy to work with. 8" 3-jaw is only used for big staff.

As far as QCTP goes I use a BXA size. It all depends on the center height of the lathe above the compound top and size of the tools you want to use. My BXA holders can hold up to 3/4" high tool shanks, bigger tools would require CXA or bigger post. The last but not least is the cost. Small holders cost less and you would need quite a few of them (I have around 24).

[The Metal Butcher]

10" 3 jaw is the perfect size for a 1440. They'll do up to 2500RPM for a good one, and can still kiss the jaws to the ways without running out of scroll. 4 jaw, 10" min, 12" max. You could run up to a 14.5" obviously but it is unnecessary. CXA is probably the right size. All depends on the compound to center-height distance.

To all commenters comparing this to their 12" lathes.... it is not. It is a 14.5" lathe. Naming conventions of yore do not compare to modern naming. Even if it only swung 12", it would still outweigh a modern lathe 3-1. It should be considered a 14.5" lathe by modern standards and a heavy duty one at that.

Also faceplates should always be sized to the max swing of the lathe. 14"+

[LKeithR]

You got an 8" chuck with the machine? Use it for a while and you'll be able to decide what else
you need. No one size is perfect for all machines or for all operators. If you're always doing
smaller, delicate work then a small, precise chuck might be better. If you're often pushing the size
limits of your machine then a bigger chuck may be in order.

At the moment I've got six chucks for my 13" machine: An older 8" 3-jaw with inside and outside
jaws, a brand new 8" 3-jaw with two-piece jaws, a 10" 4-jaw, an ER40 collet chuck, a 6" 3-jaw
which I use mostly with soft jaws and an older 8" 4-jaw. The older 8" 3-jaw sees the most use
all of them get used from time to time,,,

[BCRider]

I like Matt's idea of the chuck size being 2/3's of the swing. So that would imply that you COULD use a 10" chuck. But if you got it with an 8" 3 jaw and it didn't come with a 4 jaw then I'd make getting a 4 jaw the first priority. You'll want the 4 jaw independent for the accurate re-centering it provides. I'd call that a more important priority over a bigger 3 jaw.

As for a 10" 3 jaw? I'd go with the 8" for now and see if you run into any issues that using the outside jaws can't fix. Or for that rare time you need a bigger center hole where you can't make do with using the 4 jaw.... This assumes that the 4 jaw you get will have a bigger center bore than the 3 of course.

My own 12x36 came originally with a 6" 3 and an 8" 4. I thought at first that I'd want to go to an 8" 3 jaw. But over time I found that the 6" didn't stop me from doing very much at all. About once a year I'd want to hold something that didn't fit in the 6". But for that one time a year I'd swap to the 4 jaw and just deal with centering it up. At this point and for how often I'd need an 8" over the 6? I'm not going to bother. It's not that big a deal to swap to the bigger 4 jaw and center the part.


For certain jaw stickout fouling the ways is a thing. With the previous Myford 7 I felt I could get away with a 5" chuck. I had an inch of clearance after all, right? Turned out there was a surprisingly wide range of size I could not hold onto due to jaw stickout stopping the chuck from turning. And I don't mean right at the maximum opening. I could only open the jaws about 2/3's of their maximum. This was so bad that the maximum size I could hold in the 5" was actually a fair bit smaller than I could hold with the 4". How's that for a kick in the pants?

But with a 14.5" swing you would not be likely to run into that with a 10". Well, except perhaps during jaw changes when you wind them fully off the scroll and were to try to turn the chuck.

On the tool post idea. What is the height from the top of your compound rest to the spindle axis? Use that to decide on which size you should be using. You'll want the holders to end up roughly mid height or just slightly lower on the post so it fits in with the working. That way when you switch to the boring bar holders where the cutting edge is mid height on the holder as opposed to about 2/3's up they end up a little over mid height on the main post instead of wanting to stick up past the top edge.

There's also the issue of tool overhang. A larger post with larger holders and larger tools is going to shift the cutting tips out further from the support provided by the size of the compound. A good way to reduce chatter is to keep the cutting tip in closer to the direct solid support under or as close to under the cutting edge as you can. And if you have an option between two posts then going with the smaller of the two is going to reduce this overhang issue.

The height issue is my main concern. But if it comes down to both BXA and CXA being useable I think I'd opt for the BXA just to reduce the overhang to the cutting tip.

[skipd1]

Thanks for the great comments. I am for sure planning to get a 10" 4 jaw independent chuck, but my reason for the sizing of the 3 jaw is I may be able to return the 8 inch 3 jaw as its new and the previous owner probably would refund the cost. As to tool post sizes, the center height to base of compound is 1 13/16 inches.

Skipd1

[BCRider]

As to tool post sizes, the center height to base of compound is 1 13/16 inches.

For sure that's CXA territory then. The dovetail height on a CXA is 3". In fact to permit using the boring bar holder without the top of the holder being higher than the edge of the dovetail so the height setter doesn't work might require a riser plate.

Boring bar holder is 2 inches tall with the cutter height at half that or 1". So you'd be fine with the CXA directly since the top of the holder would still be 3/16 below the top of the post body.

BXA post is 2.75" height for the body and the boring bar holder is 1.75". So .875 half height above the cutter tip. 1.82 + .75 = 2.56". So you'd actually still be fine with a BXA even without a riser plate.

[polaraligned]

I have a 16x60 and I use an 8, 10 or 12 depending on the size of the work I am holding. For smaller stuff I don't like a chuck that is too big with those jaws flying around. I would go for a 6" 3 jaw and an 8" 4 jaw on that lathe. Just my preference.
You could use a BXA post with a spacer under it if need be. Been there, done that.

[The Metal Butcher]

6" Chuck on a D1-6 spindle looks pretty goofy.

Just sayin'.

[polaraligned]

6" Chuck on a D1-6 spindle looks pretty goofy.

Just sayin'.

Who is putting a 6" on a D1-6 spindle?

[mikey553]

I have a 16x60 and I use an 8, 10 or 12 depending on the size of the work I am holding. For smaller stuff I don't like a chuck that is too big with those jaws flying around. I would go for a 6" 3 jaw and an 8" 4 jaw on that lathe. Just my preference.
You could use a BXA post with a spacer under it if need be. Been there, done that.

I second the statement above. Small chuck is much more user friendly for small work. I did not know they had D1-6 spindles in 1938...If it is true, then 6" chuck may not work.
BXA post may be a little too short for very small tools, but you can always put a shim under the tool if this is an isolated case. Don't forget - CXA holders would cost significantly more than BXA.