Best small lathe type for single op faceplate work?

In automotive engine balancing, pistons needing a few grams of stock removal are held in a three-jaw chuck with custom jaws.



The cut is always hand/eye/experience, but usually facing off .020"-.050" from the bottom of the pin boss inside the piston skirt. Very occasionally, the top of the piston is faced to lower compression.

To dedicate a full-size-long-bed lathe to this operation is a waste of space.

The second-operation-turret-lathes I've seen don't have cross-slides, but do they exist? What machine can you suggest which can accept existing chucks, has faceplate and cross-slide capability in a small footprint? Are they at all available on the used market?

jack vines

Best way I've found for machining piston tops- I have round piece of aluminum with a hole thru the center that I chuck up in a 3 jaw and then take a light facing cut to true the face. I made up a threaded drawbar with a block on the end that I can put the wrist pin thru and then suck the piston up against the round piece in the 3 jaw against the balance pads inside the piston or against the bottom of the piston depending on the job. This is a pretty secure setup, and its easy to indicate the piston true and then tighten the drawbar. No chucking marks on the piston either. I use this setup to remachine the tops or even regroove for a different ring setup. I never really liked those flimsy jaws that grab the piston by the ring lands, but I suppose they work ok.
I don't have a dedicated machine, as it only take a few minutes to setup with what I use.
For inside the skirt, I just keep an extra chuck handy with softjaws attached, as balancing only involves removing a small amount of material.

I think this is close to what Dan is talking about. I made this a long time ago, as seen by the grime on it, but it holds the piston by the pin and allow you to face the top of the piston without actually clamping on the piston itself. A similar, but different, device could be made if you wanted to flip the piston over to machine the pin boss.

Thanks for the suggestions on workholding.

We're moving the balancer into another room and would like to consolidate the footprint of the lathe. It makes no sense to have a 4' lathe bed when the only operation requires 1' of the length.

jack vines

It's a bit upper crust for the application, but consider a Hardinge HC or HLV, or a clone thereof.