Note: Box joint slippers are not the most precision parts to machine. However any slop you can eliminate from the transmission is nice so try to make them a good fit.

These instructions are for the machining of box joint slippers in the jig that I made to fit our Colchester student lathe.

Box joint slippers are best machined to each individual box, although “sloppy” slippers could be made as spares.

  1. Measure the size of the box the slippers are intended to fit.
  2. Measure the size of the radius on the knuckle for the same box joint.
  3. Pack the slipper-boring jig with shims to make the box jig the same dimensions as the box joint.
  4. Cut pieces of phosphor bronze to length.
  5. Place in jig
  6. Clamp them, setting them up carefully so that they are parallel.
  7. Carefully set the jig up in the lathe (using the four jaw chuck). The better this is set up the better the slippers will be.
  8. Fit the boring bar to the tool post.
  9. Take cuts until the slippers have the same radius as the knuckle. These cuts are very difficult to get a good surface finish on. The non-continuous cut on a boring bar is very hard work, as the tool post tends to jump around. It can be improved by taking light cuts and leaning hard on the tool post.
  10. Next is to machine the grease grooves on the backs of the slippers. Mount the slippers in the four jaw chuck and machine the grooves with a piece of tool steel ground to the correct radius.
  11. Drill the grease hole through the centre of the slipper and de-burr.
  12. File the chamfers on the sides of the slippers to allow articulation.
  13. Fit slippers.

The slipper will bed in slightly initially, as the machined finish will be hammered off them. As long as the slippers can be fitted into the box they should be OK. In the event of them not being able to be fitted to the box then tape a piece of wet and dry paper to the surface plate and smooth off the flat backs until they fit.