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runningbear
01-26-2008, 11:28 AM
Can anyone tell me what is involved and how you go about balancing a 4 jaw chuck. My lathe seems to have a problem at a mid rpm. Thanks for your help.

Dennis Sorensen
01-26-2008, 11:37 AM
I don't think you can balance a 4 jaw chuck...?

With all the jaws removed does it cause a vibration?

What do you refer to RPM wise? Mid RPM doesn't mean much...

My lathe can run from 45 to 1500 RPM.

My experience is simply not run higher rpm's with a 4 jaw as it is inherently out of balance due to it's design.

Maybe I am wrong on this and someone can set me straight. Come on Jackie... :D

Dave Tooley
01-26-2008, 11:53 AM
By design, a four (independent)jaw chuck will be out of balance when used for it's intended purpose. Irregular shapes. They are a crude, nonprecision workholding tool.

Dave

Riflemeister
01-26-2008, 12:53 PM
When I purchased my lathe, I was attending college to get my degree in Manufacturing Technology (Machining) and the instructor was a development engineer with Claude's Buggy Works in Visalia, Ca. I mentioned to him that I had a vibration problem with my 4-jaw at higher rpm's and he told me to bring it in and we would drop by Claude's automotive machine shop and use the engine balancer on the chuck. He fitted it on the balancer with the jaws removed and after several rather alarmingly large lightening holes were drilled into the backing plate, it was running as smooth as could be. We then weighed the jaws and matched them in weight and I never had another problem with vibration at any rpm.

PPP MMM
01-26-2008, 01:55 PM
When I purchased my lathe, I was attending college to get my degree in Manufacturing Technology (Machining) and the instructor was a development engineer with Claude's Buggy Works in Visalia, Ca. I mentioned to him that I had a vibration problem with my 4-jaw at higher rpm's and he told me to bring it in and we would drop by Claude's automotive machine shop and use the engine balancer on the chuck. He fitted it on the balancer with the jaws removed and after several rather alarmingly large lightening holes were drilled into the backing plate, it was running as smooth as could be. We then weighed the jaws and matched them in weight and I never had another problem with vibration at any rpm.,,,,,,,,,,,,,,


You'r absolutely correct. That's exactly how it's done. If this doesn't help one needs to look at the spindle bearings. Not exactly the easiest job, if one hasn't have the experience needed. Also keep in mind that if you move one jaw off centre line as it's the normal case your balance is automaticly out of wack. I would say it's the spindle/bearings that bring on the vibration at particular RPM, rather then the chuck.

Shoot well
Peter

runningbear
01-27-2008, 10:26 AM
Guys, thanks for the input. After further investigation, I removed the jaws of the 4 jaw chuck and imbalance was still present at 600 rpm where it is the worst. It also does it slightly at 800 rpm. My lathe is a new Grizzly G4003G. While running at 1400 rpm and shutting it down it seems to go through two nodes of imbalance while stopping. I then removed the 4 jaw entirely and the imbalance went away, so I guess it is in the body of the 4 jaw if I am thinking correctly. I guess I need to figure out how to balance the body of the 4 jaw. Does anybody know a way to do this in house? Thanks for your advice.

primerpopper
01-27-2008, 10:41 AM
.......contacted Grizzly as of yet. Being that it is a "NEW" lathe I suspect that it will be covered under warranty. If you do contact them please enlighten us as to the results as they surely have had RAVE reviews here on BRC.

runningbear
01-27-2008, 11:51 AM
I didn't contack Grizzly on this matter as I thought I could work it out on my own. But did contact them about a problem with my steady rest and they replaced it and told me to keep the one with the problem for parts. My hats off to the folks at Grizzly. I will contact them Monday and see what they say. I reinstalled the 4 Jaw and put the jaws back in and centered them even with the outside of the chuck and then experimented with moving this jaw or that one until the balance got better. When I moved the #1 , I have them numbered, out a half turn or so the vibration went away. Now should I add weight where the number one jaw is or remove weight from the opposite side? Your help is appreciated, Thanks, Gary.

crb
01-27-2008, 02:14 PM
I chucked and centered a piece of round stock in my 4 jaw and then removed it and slid some ball bearings on the the round stock. I then balanced the assy by drilling the heavy side until the chuck would stop at random. I still get some shake when turning oddly shaped parts. There is just no avoiding it.

Before I started drilling I taped some weight to the light side until it was balanced and it was less than 2 oz out iirc. I will look at my old threads and see what the actual wgt..

PPP MMM
01-27-2008, 04:02 PM
There is a VERY BIG difference between static/dynamic balance and there is a correct way how it can be done anywhere. If I'll explain to you how it's done(I'm not very good in explaining things, that one can understand) and when you go and buy the neccessaries needed to spin the chuck and make the stand for the set up you'll be far better off to have it done by a professional firm. Even if you'd understand my explanation it's not an easiest thing to do. The complexity of being a chuck it even more complicates the issue. Both sides (back/front) need to be balanced and not just the heaviest point pointing down. For this the chuck needs to be spinning in ball bearings suspended in precise plastic bands and precisely marked while spinning and then going 1/3 of revolution one way or the other to add or relieve material from both sides where needed. Do you really want to do this????

Shoot well
Peter

Jay, Idaho
01-27-2008, 07:17 PM
You may benefit by removing the chuck from the backing plate and installing it 90 or 180 from where it is now installed. Also, make sure that the chuck is running concentric to the spindle if there is clearance in the mounting holes.

PPP MMM
01-27-2008, 08:19 PM
Sometimes the problem could be directly related to the gearbox, cluch/quick stop and everything else. My advice is: Contact the manufacturer and let them to fix it, whatever it may be.

Shoot well
Peter

Big Al
01-27-2008, 09:06 PM
Where do you start? After the lathe is level. The place to start is with the backing plate. take a facing cut (clen up cut, just cleaning the face) across the face of the plate and then mount the chuck.:)

JerrySharrett
01-27-2008, 09:47 PM
Can anyone tell me what is involved and how you go about balancing a 4 jaw chuck. My lathe seems to have a problem at a mid rpm. Thanks for your help.

Start at the beginning. Does the lathe vibrate running the bare spindle at mid rpm?

Yes-the problem is somewhere in the machine itself. Most likely the drive belt.

No-the problem is in the chuck. Like Dave says 4-jaw chucks are not micro-balanced objects.

Look guys, these small, light weight lathes that have egg-shell castings for headstocks and low quality spindle bearings will run some rough. Want something really smooth, pay $85,000 for a Monarch EE.

Monarch-Sidney has a rebuilt 1964 EE 10x30 for sale now. Only $54,100. One year warranty included.

Mike Swartz
01-28-2008, 07:22 AM
And I'll betcha it's got an AC drive in it. Quite a machine tool.

Mike Swartz

Leeroy
01-28-2008, 08:23 AM
I had some ballance problems with the 4 jaw chuck that came with my lathe also.
Most 4 jaw chucks are cast in cast iron, then machined.
Where as a 3 jaw is usualy machined from a solid billet..
Unfortunatly castings are almost never a regular uniform shape.
The machining operations clean up most of the iregularaties but some still remain in the voids in the back of the chuck that do not get machined. This is what causes most of the ballance problems.

With my chuck i didn't have access to a balancer of any kind. So what i did was to machine the unmachined voids on the back of the chuck and make them all uniform and the same size, shape and position in the chuck body. I didn't have to remove much material and i used a long series endmill with a small 1/8 radius ground on the cutting edges so as not to have sharp 90 degree corners at the botom of the voids. (Fracture points)
After the machining the chuck ran from 180 to 1500 rpm without a single vibration.. Perfect!

It's also important to realise that it is because of the use of cast iron and voids in the chuck body that most 4 jaw chucks are speed rated!
You should NEVER exceed that speed else you risk the chuck flying apart on you.:eek:.
Also when griping odd shaped jobs in a 4 jaw you can get a pretty good balance by bolting counterweights to the light side of the chuck face. (there are often slots between jaws just for this purpose) but be sensible with speeds when running setups like this..

Hope this helped:D

Cheers
Leeroy

runningbear
01-28-2008, 12:25 PM
Guys, just a note to let you know that I contacted Grizzly today about the balance problem with my 4 jaw chuck body. They are sending me a replacement at no cost. Can't beat the service. Gary.