Ball bearings between pulley and spindle

I saw an advert for an old lathe somewhere where the belt pulley was said to be mounted on a ball bearing which was then mounted on the spindle to "remove sideways belt force" (or something like that).

Is this a real machine design option or was it some gimmick to sell an otherwise ordinary lathe?

Many "old lathes" use flat belts and the pulleys are crowned to keep the belt centered.

It is possible that the crown has worn down and the pulley is flat, causing the belt to slip off. A ball bearing could be used as a wheel on the edge of the belt to keep it aligned. If the pulley crown has worn away it could be an indication that the rest of the lathe is also worn.

Paul.

Hi Rainbows

Yes this has been done in an attempt to improve the accuracy of the spindle reducing any radial forces on it.
The ball bearing and its inner driving collar that supports the drive pulley is supported by the head stock frame, the spindle is driven by that via splines or a key. in a way a spindle within a spindle.

The real spindle is supported in its own separate bearings, the only touching point is the drive key.

I am sure there are other members that may remember other companies that did this.

From Memory the German company VDF did this with one of their lathes? They also offered plain bearings for some of their lathes the objective being a finer surface finish. Even super precision bearings create some bearing noise that may affect the work finish. The Diamond turning lathes used to turn computer disks do not use ball bearings, Air or magnetic levitation bearings are used for mirror finish required.

Regards
John

My Smart and Brown lathe has such an arrangement. I only know because the pulley bearings were noisy when I acquired it, so I had to strip it down to replace them. The spindle itself runs in its own bronze bush and paired angular contact bearings (which luckily were in good condition).

Surely this arrangement is quite common (standard, even!) in pillar drills?

Certainly my Tauco works that way.

Best regards,

Swarf, Mostly!

I've changed most of the things on my lathe but i won't touch the headstock, so long as it's in good order i dont want to open that can of worms!

Michael W