The Development And Design Of A Screw Cutting Clutch For The Myford Ml7

Graham Meek recounts how he came to revise his design for the ML7 and gives advice on its making and use - Part 3

- Graham Meek

The basic dimensions of this bush for those who wish to order one are, 12 O/D, 8 I/D by 12 mm long. This could quite easily be turned from phosphor bronze, PB, but it will not have the porous nature of sintered bronze or the oil retaining properties. Therefore, an oil hole needs to be provided for the occasional squirt. Might I suggest a hole in the side of the main body extension rather than on the top where dirt and dust will congregate which will more than likely migrate into the bearing. Another Oilite bush is used at the rear of the main body for the operating shaft. This time the bush sizes are ½” O/D x 3/8” I/D x 5/16” long. This bush again can be manufactured from PB with a similar oiling arrangement. However, this bush needs to be fitted after the operating shaft is installed so any oil hole will need to be predrilled and lined up with the corresponding hole in the main body. It goes without saying that the ½” hole in the main body needs to be a reamed or bored hole in order for this bush to be a good fit. This bore also wants to be in-line with the opposite end and this can be achieved by gripping on the boss once this has been pressed into the main body. A good chuck is required for this operation. If the readers chuck is at all suspect then I would recommend using a 4-jaw chuck. Clocking the extension boss to ensure concentricity and then running the clock along the two sides of the main body to ensure these are parallel with the lathe centre-line.