# What size chuck?



## durableoreo (Dec 6, 2021)

I need an independent 4-jaw for my HF 9x20.  I started out looking for a 4" chuck but now I'm not so sure.  One clue is that back plates with M39x4 are usually for 6" chucks.  I've seen at least 1 person running a 6" chuck on a 9x20 lathe.  Is there any reason not to go with the larger chuck?


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## matthewsx (Dec 6, 2021)

durableoreo said:


> I need an independent 4-jaw for my HF 9x20.  I started out looking for a 4" chuck but now I'm not so sure.  One clue is that back plates with M39x4 are usually for 6" chucks.  I've seen at least 1 person running a 6" chuck on a 9x20 lathe.  Is there any reason not to go with the larger chuck?


Two reasons I can think of. Weight and cost.

If a larger chuck will work then go for it, but realize the size of your workpiece will be limited by how far the jaws stick out.

A larger backplate can be cut down to size.

John


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## Cadillac (Dec 6, 2021)

I use a 6” with integrated mount on my jet 9x20 works great. I do have smaller 3&4” chucks too.


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## RJSakowski (Dec 6, 2021)

I checked my Grizzly 6" four jaw and I would not want to extend the jaws for more than a 9" swing.


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## woodchucker (Dec 6, 2021)

A 9" lathe can presumably use a 5" 3jaw, and a 6" 4 jaw.
I use the above..


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## durableoreo (Dec 6, 2021)

Thanks for the advice.  I've got some engineering but almost nothing is as good as experience.

I purchased the chuck and back plate from Shars so there will be a fair amount of cleaning and de-burring needed.  250 $ with shipping.

I would have gotten a 6-jaw, too, but it was 650 $.


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## Bi11Hudson (Dec 6, 2021)

Most of my work is with 4" and 5" chucks, both 3 jaw and 4 jaw. A 6" chuck will fit but is very large, and heavy. Besides the excessive weight, there is the issue of the chuck jaws striking the shears on large work. I normally use a 12X36 Atlas/Craftsman (101.27440) and have a 7" 4 jaw that fits both machines. The 7" chuck is really too large for the Atlas machine, let alone the 9X19. But both machines have the same spindle thread, 1-1/2X8. So I acquired the large chuck for both machines. The spindle bearings do complain when I mount the chuck, especially on the small machine. And I pull the chucked work through a full revolution by hand before applying power. A good practice on most any chuck, it has paid off a couple of times on the 9X19. Just because the lathe can swing (theoretical) 9" doesn't mean it should work it at that diameter.

.


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## savarin (Dec 6, 2021)

I use a 5" 4 jaw on my 9x20, there are times when I wanted a larger on so I expect a 6" would be fine.
I did replace the spindle bearings with high quality taper rollers.
I have hit the cross slide with the jaws once and wondered what the knocking noise was.
It wore a nice 1/8th deep semi circular smooth recess on the edge of the cross slide


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## Manual Mac (Dec 7, 2021)

These are the 4 jaw independent chucks i use.
The left one is a couple yr. old Sanou 5” I purchased for my 6” rotary table.
One on the right is an Atlas/Craftsman 6” that was on my SB9 I bought it 40 yrs ago.
The Sanou 5” easily weighs twice what the Atlas one does.
I adapted a back plate for the 5” & now use it on the SB9 as well.
It’s a great chuck, very accurate & fits the lathe well.
And I think I paid about $100 bucks for it on Amazon.


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## addertooth (Dec 7, 2021)

And look at LittleMachineShop dot Com.   Many of their chucks have a "compatibility" tab.  You can see which chucks go with which lathes within those tabs.

As noted by others, larger chucks often take up more of your distance in the 20 inch direction, on your 9 by 20 lathe.  And yes, as you open your jaws, you must be more aware of whether you have clearance with the rest of the lathe (saddle/ways).

Most of these smaller lathes are at a bigger risk of running out of power (to make an ideal cut), before you run out of physical space.  A 5 inch O.D., which is cut at the ideal feed and speed, takes more power than a 3 inch O.D.   You can overcome this by going with hand-ground tools, as versus Carbide Inserts.


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## durableoreo (Dec 9, 2021)

Well, it looks different.  Took it apart to break the edges and get the grit out of it.  Seems to work fine.  Not bad for the price


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