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Jack772
02-03-2010, 10:11 PM
I have a Harbor Freight 9x20 lathe. I saw where some of them came with a 7 inch 4 jaw chuck. Mine didn't have one so I figured a 6 inch 4 jaw chuck would work just fine.
Well, I got one but with the back plate, it weights 24 lbs.
It seems really heavy. Is this too heavy for my 9x20?
Will the weigh damage anything?
Thanks,
Jack

Carld
02-03-2010, 10:34 PM
Think about how much weight you can add to the chuck with the largest piece of stock diameter and length you can get in your lathe. Do you think that will hurt? Then consider the force of turning the work.

I don't think the chuck weight is going to be an issue at all.

darryl
02-03-2010, 11:43 PM
The bearings probably have a static rating of several thousand pounds, if not more - the only issues I can see are that of manipulating the chuck so you don't damage the spindle nose threads, and the severity of the impact if you have a crash. Might be a bit more belt slippage as it comes up to speed also. If you were repeatedly using the highest spindle speeds for long periods, I might be concerned, but that's very unlikely.

Marc M
02-04-2010, 05:41 AM
...I saw where some of them came with a 7 inch 4 jaw chuck. Mine didn't have one so I figured a 6 inch 4 jaw chuck would work just fine...

You didn't miss much. I have the Jet version and the 4 jaw was just about unuseable. I used it 1 time and spent close to an hour trying to get the stock properly centered. Everytime you touched it, everything moved resulting in lots of tail chasing.:mad:

I bought a new Bison 6" 4-jaw for it and haven't looked back. It only takes a minute or two to get things dialed in now and it doesn't marr the stock like the original did.

I also bought a 6" Bison 3-jaw at the same time. It's a lot heavier than the 4 jaw and it simply hasn't been an issue. The 9 x 20's use tapered roller bearings about the same size as the front wheel bearings GM used on full sized cars where loads are considerably greater than anything you could put on that lathe without destroying it.

Willy
02-04-2010, 09:46 AM
I would not loose any sleep over the fact that I could not put a 7 inch chuck on a 9 inch lathe.
While bigger always seems better, sometimes it just doesn't make sense.
Just how far can you open the jaws on a 7 inch, or even a 6 inch chuck for that matter, on a 9 inch lathe before the jaws hit the lathe's ways?

As far as weight is concerned, the biggest concern would be spooling all that weight up to speed upon start up. Without a variable speed drive, be it vfd or dc drive, the system does get a workout when you combine the all up rotational weight of chuck and work piece when using the higher speeds, especially on a light 9x20.
But with a little common sense and planning you should not have issues.
I mean how many times are you going to be spooling up a 5"x14" piece of stock to 2400 rpm anyway?

Black_Moons
02-04-2010, 11:08 AM
IMO the only problem you'd have with weight is if the chuck is poorly balanced and shakes your machine around. (Note you have to have some stock chucked and dialed in or the jaws will be off center and unbalance the chuck)

radkins
02-04-2010, 11:54 AM
I also had the Jet version and I agree with what has been said so far, the 4 jaw that came with it was next to useless or at least it was just an exercise in frustration trying to get it set up. I made a lot of large parts on mine (some so big I had to get creative just to get them mounted and spinning :) ) and I honestly believe the only problems you will encounter is the balance and initial start up, both of which may just be more annoying than a real problem. I used my Jet for several years and used it for WAY more than it was ever meant for, since the Jet and HF are the same machine except for the color I am well familiar with what you have and what it will do. Mount that chuck on there and use it, it will work just fine so don't worry about it.

Jack772
02-04-2010, 04:21 PM
Thanks you guys.
Jack