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Jack772
12-22-2008, 03:29 PM
I have a 6 inch 4 jaw chuck that weights 23.1 lbs.
Will a chuck of this weight cause any damage to the headstock bearings or anything else on my HF 9x20 lathe?
Thanks,
Jack

Forrest Addy
12-22-2008, 03:50 PM
No. Cutting forces and designed overload (collision, tool breakages, and similar casuaties) far exceeds the weight of any chuck you can mount on your lathe.

Steve Steven
12-22-2008, 04:57 PM
I put a similiar 4 jaw on a HF 9X20, the major problem I had was the clutch would slip if run on high speed.

Also, be sure to put the holding device on. I didn't at first, when I accidently started in reverse, the chuck spun off and danced down the bed!

Steve

oldtiffie
12-22-2008, 05:41 PM
On any "plain bearing" machine I make sure the bearing lubrication is done and then either start it on lowest speed or pull it around/turn it three or four times to get the bearing and journal surfaces "wet" and the "oil wedge" (re)established before I use a higher speed and/or put any load on.

The very thin oil film can be "squeezed" (out) which may result in a "dry start", which while any amount of bearing loss/scoring/damage may be minimal is none-the-less increasing incrementally over time.

This is usually the more so at the front bearing where the load of work and/or chuck/face-plate can be very considerable.

That would be a shame as it is largely preventable.

ammcoman2
12-22-2008, 06:27 PM
When I had my 920 lathe, I bought a 6", 4 jaw but I don't think it was 23 lbs, even with the backplate. On the other hand I made an 8" faceplate from a backplate and it weighed a ton! Never any problem on the lathe with either. If you have any concern you can always start the motor with the belt tensioner in the release position and then ease it into play.

BTW those lathes have tapered roller bearing front and back so static weight issues are probably zero.

Geoff

Jack772
12-22-2008, 08:46 PM
It weighs 23.1 lbs. I used a scale that I know was accurate.

BillH
12-22-2008, 09:10 PM
It weighs 23.1 lbs. I used a scale that I know was accurate.

As Forest said, the cutting forces FAR exceed the weight of the chuck.

Ian B
12-23-2008, 06:11 AM
As the others mentioned, the weight's not a problem. Just watch that the jaws don't hit the bed when they're fully extended from the body - I have a small lathe without a gap bed, and the 4 jaw's jaws can *just* touch the bed.

Ian

Jack772
12-23-2008, 07:39 PM
Thanks to all for your help. I feel ok about using it now.
Thanks.
Jack

radkins
12-23-2008, 07:56 PM
No problem, I have been using one on my Jet 9x20 since I got it and even though I have never weighed it I am sure it will weigh over twenty pounds backing plate and all. The Jet 9x20 is the same lathe as the HF just a different color.