Three pulleys in each set are shown. The material selected is aluminium and as I have some reservations about screw threads and that metal the design has evolved to get rid of screws in the construction as far as possible. Only the large driven group have the through bolting, the driving set is solid. Apart from having the correct groove size and therefore the right cutting tool the start of each batch of grooves has to be set in by the same amount and that also says the individual widths of pulleys have to be exact on both groups to ensure true running is the result and not running off. One has a little latitude as the driven group are built up so it is possible to rectify errors. The driven group comprise a master pulley, the middle one, in to which the other two fit with registers. The largest one has a large hollow end of 40 mm diameter. In both driven and drive the pulley group is held to the shafting with the inevitable keyway and a draw bolt from the outer end picking up a thread in the shaft. I see no alternative to a key in this work as the drive has to be positive and capable of overcoming the cutting forces, which can be relatively high.
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