Figure 8 shows a drawing of the 8 mm film roller. Face the end of the 10 mm acetal rod, centre drill, then drill a 3.2 mm hole to a depth of about 18 mm. Fit a revolving centre in the tailstock to support the work piece. Turn down to 9 mm outside diameter (OD) for about 16 mm, and then change the lathe tool to the form tool. The form tool places an increasing load on the work piece as it is fed into it and cuts across more of the width of the tool so progressively reduce the feed in rate. Make sure the square shoulder is formed to the required depth and the OD of the centre of the roller is 5 mm. Part off to length of 12 mm with a parting tool ground at an angle to cut through at the base end of the roller to create a clean base surface. Advance rod in chuck, face end, extend 3.2 mm hole to about 18 mm, fit revolving centre and repeat turning operations. Any small variations in length can be accommodated by the method of mounting on 3 mm threaded set screw used as axles and adjustment nuts. A typical film roller mounting can be seen at the top of Photograph 13 (see mechanism > framing arrangements).