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old blue
12-23-2009, 08:23 PM
I finally got this lathe http://bbs.homeshopmachinist.net/showthread.php?t=33711 to the point I can turn it on and what do I find? a vibration.
I have eliminated most of it by shimming, but at 1000rpm it is still there.
At 1500rpm(machine max) you can just Hardly feel it, 650 and down I think it is gone. What else can I check?

Black_Moons
12-23-2009, 08:29 PM
Oh man poor guy.. I think I would of refused delivery or gotten the freight company to pay through the friggen nose for that kinda screw up.

Do you have a chuck attached? a 4 jaw chuck with one jaw thats further out then the rest can cause vibration.

How much is the lathe vibrating? (Maybe a test dial indicator mounted to something nearby that isent vibrating?)

old blue
12-23-2009, 08:50 PM
The machine was delivered by the cousin of the guy I bought it from, on
a roll back truck.
It has a 6 jaw chuck. I had not thought of the indicator thing.

Ken_Shea
12-23-2009, 08:54 PM
Maybe try removing the chuck and see what that does.

I hate vibration hunting, can be a real pain.

The Artful Bodger
12-23-2009, 08:57 PM
Is the vibration there when the chuck if off?

nheng
12-23-2009, 09:15 PM
The chuck looks like it is a "set-tru" (or other similar name) type which has screws aroung the perimeter that allow centering of the chuck body and jaws.

Typically, you would install a precision round rod like a piece of drill rod, end mill shank, etc., loosen the screws on the face then snug them down lightly. The screws (probably 4) around the perimeter (2 plus another hole showing in your photo) are then adjusted to center the chuck body. These adjusting screws, on Buck and some other chucks, are not intended to be super tight but only to push on an internal hub to center the chuck. The face screws are the ones that should be torqued afterward and do most of the work.

So, my 2 thoughts are a) the chuck is adjusted way off center (although it doesn't necessarily take much) or b) belts in your drive system.

Belts will go in and out of resonance at different speeds and bounce like a son-of-a-gun as they do. Watch the belts while you change between "quiet" speeds and one with vibrations. The cure here could be belt tension, new belts or both.

Den

old blue
12-23-2009, 09:26 PM
The chuck looks like it is a "set-tru" (or other similar name) type which has screws aroung the perimeter that allow centering of the chuck body and jaws.

Typically, you would install a precision round rod like a piece of drill rod, end mill shank, etc., loosen the screws on the face then snug them down lightly. The screws (probably 4) around the perimeter (2 plus another hole showing in your photo) are then adjusted to center the chuck body. These adjusting screws, on Buck and some other chucks, are not intended to be super tight but only to push on an internal hub to center the chuck. The face screws are the ones that should be torqued afterward and do most of the work.

So, my 2 thoughts are a) the chuck is adjusted way off center (although it doesn't necessarily take much) or b) belts in your drive system.

Belts will go in and out of resonance at different speeds and bounce like a son-of-a-gun as they do. Watch the belts while you change between "quiet" speeds and one with vibrations. The cure here could be belt tension, new belts or both.

Den


I did find that the drive pully on the motor has about .006 run out.
I know there is a way to test/check belt tention(By how far you can push it
in the middle of the span?) can some on refresh my memory.
The chuck is indicated in.

old blue
12-23-2009, 09:27 PM
Maybe try removing the chuck and see what that does.

I hate vibration hunting, can be a real pain.

I will have to try it with the chuck off.

Ken_Shea
12-23-2009, 10:18 PM
Old Blue,
Cant say for sure but lathe drive belts are fairly tight, not banjo string tight but (just guessing) 3/8 - 1/2" deflection at mid point, my lathe has even less.

Den, has brought up a good point, also be sure the pulley grooves are clean.

.006 seems high to me, that could be a source of your problem but you did say that was at the motor, if that is cause for vibration it would be somewhat absorbed through the belt system.

JoeFin
12-24-2009, 12:24 AM
.006 I would beleive is excesive

I just re-shimmed a drive pully for a machine that had a simular amount of run out.

winchman
12-24-2009, 12:48 AM
Using a dial indicator to see how much it's vibrating sounds like a bad idea.

In the first place, the indicator mechanism isn't made for that, and it may be permanently damaged. Secondly, the needle swing won't tell you much since most of the amplitude will be the result of the needle flexing.

I'd clamp a pan of some sort to the bed, and put a little water in it. The ripples will tell you when the vibration is worse. By changing gears to vary the spindle speed you might be able to determine what part of the drive train is responsible for the vibration.

My lathe ran much more smoothly after changing from the original V-belt to one with links.

Roger

old blue
12-24-2009, 09:40 AM
.006 I would beleive is excesive

I just re-shimmed a drive pully for a machine that had a simular amount of run out.

I was thinking of doing the same thing, but with .003 to .004 cl you would only get maybe a .001 shim in there. How did you do yours?

Bill Pace
12-24-2009, 10:24 AM
changing from the original V-belt to one with links.

I've had this simple fix to take care of 2 different lathes with vibration. The one I'm using now was pretty similar to your description, the belt was one of those Chinese things with a 'bump' in it.

I keep takeoff belts from this or that, and digging through the box found a used one same size and put it on the lathe to try and isolate the vibration and whoa! what a difference! - later I replaced it with a link.

JoeFin
12-24-2009, 10:36 AM
I was thinking of doing the same thing, but with .003 to .004 cl you would only get maybe a .001 shim in there. How did you do yours?

I bored it out from .75 to 1.25. Pressed in Bearing Bronze .001 over. Rebored it to .75 and cut in the keyway.

It was a 6" wide x 8" dia. drive pully covered with neoprene 1/2 thick for a big commercial cabinet shop edge sander. The Neoprene had "Hi and Low" spots all over it from the wobbly loose bore before I fixed it. I had to also sand the neoprene concentric and beveled again.

The guy keeps coming back - I guess it work alright

JoeFin
12-24-2009, 10:41 AM
We used to have a Stobe-Vibration Detector at a place I worked at years ago. It had a pick-up with a little LED on it you could tune manually by ear to match the problem vibration. You then pointed the syncronized Stobe light at the whirlling parts of the machine and the problem child would appear to be standing still in the strobe light.

To bad there is not an easy way to rig up an automotive timing light to do the same thing......... Evan ?????

old blue
12-24-2009, 10:52 AM
I bored it out from .75 to 1.25. Pressed in Bearing Bronze .001 over. Rebored it to .75 and cut in the keyway.

It was a 6" wide x 8" dia. drive pully covered with neoprene 1/2 thick for a big commercial cabinet shop edge sander. The Neoprene had "Hi and Low" spots all over it from the wobbly loose bore before I fixed it. I had to also sand the neoprene concentric and beveled again.

The guy keeps coming back - I guess it work alright

Thats how I fixed the driven pulley on the other end of the belts,
the key way was worn out on that end. But I don't think there is enough
material to do that with this pulley. I would just get a new pulley but
the foot break drum is part of the pulley so I may have to make a new one.

old blue
12-24-2009, 10:55 AM
My lathe ran much more smoothly after changing from the original V-belt to one with links.

Roger

Is that the type of belt that you can remove links like a chain to change the length?

JoeFin
12-24-2009, 10:55 AM
Thats how I fixed the driven pulley on the other end of the belts,
the key way was worn out on that end. But I don't think there is enough
material to do that with this pulley. I would just get a new pulley but
the foot break drum is part of the pulley so I may have to make a new one.

If its not too thick you could possibly weld it up with Ni rod and bore it concentric again.

old blue
12-28-2009, 08:43 PM
Did some investigating tonight. I tightened up the belts at the vibration seemed to get worse. I took the chuck off, the vibration was less but still there and at the same rpm. I ran the motor with the spindle in neutral
and still had some vibration. I am almost thinking the run out on the
pulley may be the cause, and the chuck is amplifying the problem.

vikingsword
12-28-2009, 10:54 PM
Just a thought here that you might check out the motor bearings? Wes

Black_Moons
12-28-2009, 11:02 PM
Yea, next step would be take the belt off and see how the vibration is. If its still bad.. take the pully off the motor.. if its still bad... new motor? :)

winchman
12-28-2009, 11:05 PM
"Is that the type of belt that you can remove links like a chain to change the length?"

Yes. I got it from McMaster-Carr, but lots of places carry the same thing. Mine is red "twist-lock" found on page 1033.

Roger