The headstock spindle fitting is the American L type. This consists of a large screwed ring, captive on the headstock spindle, with a matching thread and keyed taper in the chuck backplate. If you have a sample with which to make comparison, all is well, but it is very easy to believe that the fitting either side of the one you need is correct. Screwcutting and Power feeds The Student and Master were both produced in a variety of specifications and, although most were fitted with a screwcutting gearbox, numbers were supplied to training workshops with either English or metric screwcutting using changewheels. The leadscrew on all Students and Masters is used only for cutting threads - and should normally be left disengaged.
All models have a shear pin incorporated in the top gear of the screwcutting drive.
When the leadscrew and power shaft won't rotate, this is the first place to look. All versions were provided with a dial thread indicator as standard. The main differences between the Mk1 and Mk2 machines are found in the design of the headstock and apron. Colchester installed new gear-cutting machinery and the improved parts went into the redesigned lathes. Power sliding and surfacing on the early machines is selected by a lever which slides horizontally along the base of the apron and lifts into one of two slots.