8" 4 Jaw Chuck Balance Issue

[verbotenwhisky]

Has anyone here ever had an issue with a chuck being out of balance to the point that it causes the lathe to shake? I think I may have cause a bit of the issue, I knocked some loose slag out of the back of it; but, I would like to balance it and input would be appreciated, can I use stick on weights? should I drill lightening hole? slowly grind small amounts of metal out? or is it worth messing with? I would like to know what others think.

 

[markba633csi]

Is it out of balance with all the jaws removed? If the body itself is way off then yes you could remove material.
Since they are made to hold odd shapes there are many occasions when the job will be unbalanced and that limits the speed

 

[Ischgl99]

It depends on how badly it is out of balance as to whether it is worth messing with. If it’s a little bit worse, I wouldn’t mess with it, but if this is shaking the lathe, I would. If you start drilling or grinding, you can easily make it worse. If your chuck has an open back, I would use stick on weights instead of drilling or grinding, they are easy to remove if you mess up. You can probably get them at an auto parts store, if not, McMaster-Carr carries lead stick on weights.

Before doing any balancing, make sure you eliminate any other possible causes for the vibration, ie chuck jaws at different positions, chuck not mounted correctly, something loose on your lathe, etc. You can do a trial and error method, or there are apps you can use for smartphones to measure the vibration of your machine to get more accurate results. I haven’t used any of those yet, so can’t say if they are any good. You can use the 4 run balance method by placing trial weights at different locations and taking measurements for each run to calculation how much weight and where to put it. It may take you a few tries to get the hang of it, but with stick on weights, that is easy enough to do. The following link explains how to do it.

HowTo: Single-Plane Rotor Balancing with Single-Channel Four-Run Method – Motionics LLC

motionics.com

 

[Charles scozzari]

Thats interesting, I guess you only use the 4 jaw for shafting. The only way I could think this is possible is to disassemble the chuck and dynamically balance the outer shell and scroll, then static balance each of the jaws and related parts separate., The only thing I believe is once you lock the work in the chuck the balancing is gone. Do you have a three jaw to try. I know this is a silly question, but without a mounted chuck is there any vibration at the lathe spindle. If your working between centers is the tail stock dead on aligned. Hope that helps a little. Thanks.

 

[Just for fun]

I static balanced mine, and it was big improvement. Here is a thread that shows what I did. I just glued weights on, once I determined how much I needed.

Chuck Balancer

Made a unit to check the balance of my 4-jaw chuck. I bought a bicycle exerciser unit at a secondhand store for $5 bucks a while back. I disassembled it and turned a couple of bearing holders and a shaft to go between them. It seems to work, the best I can tell it's a little over a half ounce...

www.hobby-machinist.com

 

[Dabbler]

Some basic tests: have you indicated the chuck body?

Chuck up a piece of cold rolled or centre-less ground stock, at the centre of rotation, and than make an improvised balance stand. you can easily get a feel for how unbalanced the chuck casting is. Your 4 jaws won't be more than a couple of grams off from each other, so there wouldn't be any worries about them.

Of the dozens of 4J chucks I've used this is an anomaly. If you prove that the chuck is balanced this way, you can begin to look for other sources of vibration. I'm worried that your headstock is bent. Now that I have seen.

 

[Charles scozzari]

I static balanced mine, and it was big improvement. Here is a thread that shows what I did. I just glued weights on, once I determined how much I needed.

Chuck Balancer

Made a unit to check the balance of my 4-jaw chuck. I bought a bicycle exerciser unit at a secondhand store for $5 bucks a while back. I disassembled it and turned a couple of bearing holders and a shaft to go between them. It seems to work, the best I can tell it's a little over a half ounce...

www.hobby-machinist.com

I'm gonna use my old bubble wheel balancer. Just kidding.

 

[mksj]

I had that occur with the Chinese 4J that came with my first lathe, if one looked at the back of the chuck casting it was extremely uneven. Couldn't get the chuck past around 350RPM with the lathe shaking pretty bad. It is usually exacerbated using a VFD as you can hit the vibration nodes when changing speed. I relegated that chuck to my rotary table. It was replaced with a Taiwanese made 4J independent that was much better cast and also had balance weights on the inside of the chuck. It was smooth at all RPM's.

 

[Cadillac]

I had a similar problem with my 4jaw. I have a 14x40 lathe with a sheet metal base. The chuck is direct mount d1-4 with a open back. First time I mounted it and spun up the lathe everything was good until I adjusted the speed. I have a vfd. Between 500-575rpm the lathe wanted to rock or wobble. Go the 475 no problem go to 625 no problem pretty smooth but could feel a minor shake in the whole lathe.
My solution was I chucked up a piece of 3/4 precision ground rod about 12” long. Half stuck out the front and half out the rear of chuck. Centered the rod with a tenth indicator so it didn’t move. Then I have a balancer for my grinding wheels that I used. I placed magnets strategically to get the chuck balanced. Once balanced I weight each magnet and ground out the spot where it was the weight amount of magnets.
Doing so took up 80% of the shakes. I found that my lathe itself doesn’t like rpm’s between 500-600. Even with my 3jaw is has a minor shake at those rpm’s. I can’t say I have tried it with no chuck just the spindle to see.
. My lathe has a foot brake which the mechanism is under a pulley within the drive. My thought is the pulley itself is unbalanced and throwing the lathe off. Their is only the motor and pullley a belt and the pulley I speak of that drive my lathe. Motor decoupled spins smooth as glass. Belts on all other drive gears decoupled it has the shake at those specific rpm’s. Haven’t dug further into it. Sheet metal base is undesirable if reinforced as much as possible. I wish it was a cast.
Back to the chuck yes you can balance but you want to be absolutely sure of where and how much you take off. You can definitely make it worse. Once you have the magnets correct you could just epoxy in place instead of removing weight.

 

[verbotenwhisky]

Is it out of balance with all the jaws removed? If the body itself is way off then yes you could remove material.
Since they are made to hold odd shapes there are many occasions when the job will be unbalanced and that limits the speed

Yes with the jaws out, I had the same thought because it was fine then it wasn't.