Unimat 3 power feed attachment.

I've recently aquired a power feed attachment* for my Unimat 3. But before I go any further I'd better describe what exactly it does. When you take a cut on a lathe you feed (move) the tool along the job using the appropriate handle. On larger, more expensive lathes the saddle (the part that moves along the lathe bed which the tool post sits on) can be moved under power, saving a lot of handle twiddling and resulting in a smoother, more even cut. Both the Unimat SL and 3 can be fitted with power feed.

I managed to win one on eBay;

 Looking at it from the 'back';

A drive belt runs from the headstock spindle to the upper pulley shaft which has a worm on it. Drive is transfered via a gear on the bottom shaft to the lathe's leadscrew (the long threaded rod which runs along the front of the machine and is connected to the saddle). Note the slot in the end of the bottom shaft, this connects to the end of the leadscrew which is already machined to suit.

The unit attaches to the machine with a single 6mm bolt;

To fit the drive belt the main spindle pulley needs to be removed, this simply unscrews. A tommy bar can be used to lock the spindle when removing the pulley. In the photo above the belt can be seen in place, note how its twisted through ninety degrees.
Spindle pulley back in place;

Feed is engaged or disengaged by pushing in or pulling out the black knob, which moves the bottom shaft along bringing the gears into or out of mesh.

An overall look at the machine with the attachment fitted;

The feedrate is .02mm per revolution, that is when the feed is engaged the saddle moves along the bed by .02mm for every full turn of the chuck, regardless of the spindle speed. This gives a nice smooth surface finish.

There are no bearings inside the attachment, the shafts running straight into holes bored in the casting, so regular lubrication is pretty essential to prevent undue wear.

Hopefully this will be a usefull accessory, I've already used it when flycutting the end of a length of bar as preparation for turning a chimney.

Paul.

*Also known as a 'self-act' in some quarters, although its not a term that I'd ever heard until I started reading up on Unimats and model engineering in general.