Turning the lathe into a vibrator

[tracebender]

I have a 7x12 which runs nicely with the 3 inch 3 jaw chuck that came with it. I've had a four inch 3 jaw chuck and adapter plate laying around for quite some time so I thought I'd give it a go and see how it works. After bolting it up to the lathe I notice that it has some good vibrations. Looking at the run out on the adapter plate the center hole seems to vary by about .004. Looking at the collar that the chuck rides on I don't see this much variation, more like .0015. Is this typical of adapter plates? (I don't recall if it came with the mill or I bought it from LittleMachineShop)

How do you go about balancing a chuck to eliminate vibrations?

[tracebender]

I took the chuck off and just mounted the adapter plate and still have the vibrations. By tapping on the plate while monitoring the test indicator as I mount it I can get it pretty well centered with run out less than a couple thousands but I still have vibrations when running with just the adapter plate. When I take the plate off the machine purrs nicely and there is almost no run out noticeable on the original spindle.

Has anybody swapped to a four inch 3 jaw chuck on their 7x lathe? What was your experience?

[WaveDude]

I have the 4" 3-Jaw + Adapter plate from LMS. My adapter plate was a bit "off" in that the center-register hole was too big for the spindle. Good if you want to tap it around like a set-tru chuck to get it perfectly centered but too much fuss for me. I have a 4" 4-Jaw + Adapter from LMS as well. That adapter fit much better so I swapped it over to the 3-Jaw (since the 4-Jaw you dial in every part anyway so it didn't matter if it was mounted off some).

That said--I do get some vibrations from the 4" 3-Jaw. Some go to the trouble of balancing them out. I'm not that fed up with it yet.

Have you tried mounting it all the different locations possible to find the one that vibrates less?

[tracebender]

The center hole in my adapter is larger than the spindle hole as well but I didn't think that much of it. I did try mounting the adapter and chuck in the different positions but there isn't much difference. I can't try a test cut yet since I'm doing some work on the cross slide.

I was thinking that to achieve better balance I could drill a hole some round stock and insert a screw and washers. Then, rotating the stock in the chuck to different positions, running the lathe each time, and see at what position the vibrations are minimized. I could then subtract some weight from the opposites side of the adapter plate by drilling a hole. Does that sound like it might work?

[wildwestpat]

Hi Folks

The chuck back plate recess should be a snug fit on the spindle register. The mounting screws should have clearance holes in the back plate and only serve to clamp the parts together that all important recess is I am afraid in your case too big and you need to make a new back plate or repair the existing one. The machining is straight forward on a face plate and well worth the small amount of time involved. If you have bit of scrap material the offending recess could be opened out and a pug / bush locktited in place and then machined to the correct dimensions for the spindle / chuck once the bush has been glued in place with locktite.

I have a run out that is less than 0.0015 inch on both my four and three jaw self centering chucks measured on the ground outer body of the chuck.

Hope this helps as tapping the chuck to center it is going to get repetitive and if too enthusiastic not good for the headstock bearings.

Regards

Pat