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Too much chuck for my lathe?

iceman1

Plastic
Joined
Sep 19, 2017
Hi all,

I'm new here and have a question for anyone.

I have a 9in. South Bend Model C lathe and I just bought a 6 in.
TOOLMEX chuck. What a beast! It weighs 21 lbs and the back plate
is another 11 lbs. Is that too much weight for the spindle of my
poor little lathe? Any ideas?

Thanks!
 
Hi all,

I'm new here and have a question for anyone.

I have a 9in. South Bend Model C lathe and I just bought a 6 in.
TOOLMEX chuck. What a beast! It weighs 21 lbs and the back plate
is another 11 lbs. Is that too much weight for the spindle of my
poor little lathe? Any ideas?

Thanks!

your limit is rpm limit on chuck before it flies apart in pieces and usually you get vibration from unbalanced load. many a lathe cant go too fast a rpm without shaking vibrating too much
 
Thanks for the reply. I was more worried about the weight hanging off the end of the spindle
than the speed. This chuck is rated for 3500 RPM so I'm not worried about that.

Thanks again!
 
Those numbers seem high. How can a 6" chuck weigh a lot more than any other 6" chuck? If the lube system is up to snuff, I wouldn't expect a problem. What I worry about more is when I see chucks cantilevered far from the bearing.
 
Another consideration (beyond max RPM) is the strain a heavier chuck places on the flat belt drive. I've got a really nice 8" 4-jam Rohm chuck for my Logan 920 (11" swing)...but it's arguably oversized, relative to the original 6" Cushman or similar that came with the Logan. The lathe can handle the larger chuck, but the drive belt sometimes slips on start-up.

The other side of the extra weight is that a heavier chuck has more mass to power through deeper cuts (inertia)...but the squeal/slip on start-up is (in my opinion) disconcerting and not usually worth it. If I'm looking for precision I mount the Rohm. If I'm looking for day-to-day use I mount a lighter chuck.
 
Those numbers seem high. How can a 6" chuck weigh a lot more than any other 6" chuck? If the lube system is up to snuff, I wouldn't expect a problem. What I worry about more is when I see chucks cantilevered far from the bearing.

This is the fine adjust, forged steel chuck. The specs are 21 lbs and I believe it, it's heavy.
 
Another consideration (beyond max RPM) is the strain a heavier chuck places on the flat belt drive. I've got a really nice 8" 4-jam Rohm chuck for my Logan 920 (11" swing)...but it's arguably oversized, relative to the original 6" Cushman or similar that came with the Logan. The lathe can handle the larger chuck, but the drive belt sometimes slips on start-up.

The other side of the extra weight is that a heavier chuck has more mass to power through deeper cuts (inertia)...but the squeal/slip on start-up is (in my opinion) disconcerting and not usually worth it. If I'm looking for precision I mount the Rohm. If I'm looking for day-to-day use I mount a lighter chuck.

Seriously - while it may be disconcerting to you, .........a bit of belt slip is nothing to worry about, .....and CAN save your ass - especially on lighter lathes.
 
Good info here. Thanks. I modified the original drive to accept a v-belt. And
mounted a dc motor so I don't have to stop all the time if I want to change speed
or direction. The original chuck is an old 6 in Craftsman semi-steel. It only weighs
about 6-7 lbs, if that. Actually not a bad chuck, all things considered.
 
Those numbers seem high. How can a 6" chuck weigh a lot more than any other 6" chuck? If the lube system is up to snuff, I wouldn't expect a problem. What I worry about more is when I see chucks cantilevered far from the bearing.

21 lbs sounds about right for 6" 3-jaw chuck.

to OP's guestion: I would pay more attention to how far the jaws are going to extend if you mount something in the chuck. 6" chuck for 9" lathe is definitely on largish side.
 
21 lbs sounds about right for 6" 3-jaw chuck.

to OP's guestion: I would pay more attention to how far the jaws are going to extend if you mount something in the chuck. 6" chuck for 9" lathe is definitely on largish side.

I suppose I can always put this up for sale and go to a 5".
 
There is another concern: longer overhang. The original chuck with my lathe was a 6" Buck adjust-tru with one piece jaws. I bought a 5" Bison with 2 piece jaws. The overall length of the Bison is about 1 1/4" more than the Buck. That means I can have less work sticking out of the Bison without experiencing chatter.
 
Oh boy I've done that a few times.

Only once for me, but nearly lost my left index finger. So now I don't care, i'm careful with 2x4's, straps, cranes and all, but ultimately I will let any POS chuck roll off and fall on the floor, before my hands goes underneath while popping it off the taper. My fingers are way more valuable, than any chunk of Metal.


('course the smallest Turning chuck in the building is 12", biggest is 36" 4 jaw)

R
 
Completely agree. Maybe disconcerting is an overstatement.

Nothing wrong with a little belt slip, the slip can be beneficial from a safety point of view, and it doesn't stop me from using the Rohm when it's the best chuck for the job at hand.

But it is a significantly heavier chuck than the others I've got...and the extra mass causes it to slip considerably and more often- which leads me to select a lighter chuck for day-to-day.
 
while the 5"ers are MUCH better suited to a 9" the weight of the chuck is of no concern.....until you smash your fingers taking it off.:)

For my 13" lathe I made chuck blocks from 4x4s. They est on the bed and cradle the chuck when installing or removing it. I am considering doing the same for my 10K.
 
while the 5"ers are MUCH better suited to a 9" the weight of the chuck is of no concern.....until you smash your fingers taking it off.:)

Why is your wife changing your lathe chucks?

To add some technical merit- a 6" diameter steel slug 3.5" tall with a 25% void (SWAG'd all numbers) calculates to 20.89#, so ya 21# sounds fair. Beats the hell out of swinging my 8"
 








 
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