Wobbling lathe - ideas or suggestions?

S

skipkh

New member
Here's the scoop.... I have an Emco Super11 Lathe (11"x25"), that I have properly leveled on a concrete floor. It is not bolted to the floor, but it weighs about 600#.

When I use the 4-jaw, let's say to cut a chamber, it works beautifully. However, when I mount anything between centers using a lathe dog to drive the piece, it wobbles like an out-of-balance washing mashine in the spin cycle! It seems obvious... the weight of the dog spinning around off-axis is causing a wobble. I can't possibly be the first person to experience this, but I can't seem to come up with a solution for times when I need to machine between centers. How do you all do it and avoid the wobble?

Thanks!

Steve
 
Are you useing a face plate to drive the dog? If so does it have just one slot for the dog? That could cause it to be out of balance. Try useing the 4 jaw and chuck up a pice of steel and cut a center, 60deg, levee it in the 4 jaw and drive the dog with a jaw.
 
Thanks for the reply! No, I'm not using a faceplate - don't have one. The spindle in my lathe has a blind hole about an inch out from the edge of the spindle bore that a 'driver' screws into - basically a 2" post that screws into the spindle. this drives a clamp or straight-legged dog.

Would driving the dog with the 4-jaw chuck improve things over my current arrangement?
 
Bolt that baby down.
If your floor is concrete use drill in anchors and shim as needed.

Chuck
 
The 4 jaw should help I bet that 2" pin that drives the dog on your lathe does not help the balance because you have the weight of a 2" pin plus the weight of the dog all on the same side I would also use the smallest size dog you can.

Hope this helps

Ryan
 
Thanks Ryan! I considered that, and my possible solution was to machine that pin out of aluminum to save weight. I'm using the smallest dog that will hold the 1" diameter piece I am machining though... so is it fair to assume that this is a known issue when using a dog on a lighter lathe? Can I assume you guys have faced this issue (no pun intended) before on your own lathes when using the lathe dog and turning between centers?
As for bolting it down, Chuck, unfortunately I am not permitted to drill into the concrete, otherwise I would have.

Seems like the industry would have come up with a lathe dog that is balanced, or had a provision to counter-balance it. But in all my searching, I haven't found one yet.
 
Thanks Don!

I was giving this some more thought.... in addition to using a balanced dog, like the one you mentioned. Could my spindle speed been affecting this? I have been running 200RPM to get the FPS right for the material I am cutting, but maybe I need to slow it down when using the dog and between centers?

P.S. Still loving my Micro Set Neck Turner - 5 years and counting - thanks Don!
 
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Skip

I'm new to this whole Lathe/Machining thing, I'm still learning but, have been paying attention. I had a similar problem when I was truing a bolt face. At 600rpm I got a slight wobble in my machine, I changed to 800 rpm and the wobble stopped. I used a Lathe Dog when I was turning down a piece test stock between centers to set my tail stock center. I used 800 rpm and made passes at a Feed Rate of .005" per rev. and was removing .010" of material at a time, no wobble. Good luck to ya.

William
 
When

I went to gunsmithing school some 25 years ago we had lathe drive plates that mounted on the spindle. This is not the same as a faceplate. Don't think anyone makes them anymore. I did find one on ebay that used a D1-4 mounting but got outbid. If you search on ebay you might find a picture of one of these. Matter of fact I think I'll do that right now. Bye.

Yep, several on ebay. Most common terminology seems to be "lathe dog drive plate". Still kicking myself for letting the D1-4 get away.
 
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Why don't you just bolt a counterbalance to the other side?

Grab a step block or clamp and bolt it fast at some diameter that roughly balances the weight of the drive dawg. Then, don't run the chuck at unsafe speeds when using a 4 jaw with an out of balance setup. bad things are bound to happen.

A T-slot nut and hunk of steel FIRMLY attached will fix the balance. But again, you're running too fast for that setup. jmho...
 
skipkh said:
Seems like the industry would have come up with a lathe dog that is balanced, or had a provision to counter-balance it. But in all my searching, I haven't found one yet.
Click to expand...

Counter-balance the lathe dog yourself by drilling and tapping for a bolt and multi-nut setup opposite the the drive arm.

Your biggest problem is the 600 lbs weight of your fine Emco lathe, although great quality it is too light to accomodate any off balance machining without creating undo oscilllations.............Don
 
unless i missed it

Someone has yet to suggest........getting a faceplate.

The extra spinning mass will help hide the small dogs weight !

Sounds like you need one anyways :confused:
 
Keep in mind that the distance from center will magnify the inbalance...the closer to center, the better.

BE CAREFUL if you try to counterbalance the dog with added weights.......anything that comes off, even at 200 RPM, can cause serious harm.

Serious wobble at only 200 RPM is a little unusual.......does that dog have any built-in counterweight at all? The drive pin you mentioned must be the big contributor. Using a minimal size pin may be the best solution, short of a face plate.

-Dave-:)
 
skipkh said:
Here's the scoop.... I have an Emco Super11 Lathe (11"x25"), that I have properly leveled on a concrete floor. It is not bolted to the floor, but it weighs about 600#.

When I use the 4-jaw, let's say to cut a chamber, it works beautifully. However, when I mount anything between centers using a lathe dog to drive the piece, it wobbles like an out-of-balance washing mashine in the spin cycle! It seems obvious... the weight of the dog spinning around off-axis is causing a wobble. I can't possibly be the first person to experience this, but I can't seem to come up with a solution for times when I need to machine between centers. How do you all do it and avoid the wobble?

Thanks!

Steve
Click to expand...
Can you post a picture of the setup?
 
slow it down with that light of lathe you cant run something out of balance very fast. are your center holes near center? is your head stock center runnig true? is the dog floating only hitting enough to drive work.
 
Head stock is running dead true - and the dog is contacting properly. Oddly enough, I switched dogs last night and the problem is greatly minimized! Looks like this all comes down to careful balance - thanks all!
 
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