On Sunday 08 November 2009, Ian W. Wright wrote: >One thing you could try is the way I have just made a set of >toothed belt pulleys for my new little gantry mill. I used >'Polymorph' (Jett Sett) and the way I did it was to get a >long belt of the pitch I wanted and a bit wider than I >intended to use. I chopped a length off htis of the right >number of teeth for the pulley being careful to cut it at >the root of one of the teeth so that, when I put the ends >together, the pitch was maintained. Now I turned a recess in >a piece of metal or acrylic ( I used scrap bits of both for >different pulleys) so that the belt would just fit into the >recess with its ends tightly butting - that was the plan >anyway but I actually ended up with the recess a bit larger >in diameter and shimmed it down to size with paper strips. I >drilled the centre of this mold and put a peg in of the >diameter of the shaft the pulley was to fit and then turned >a brass hub for the pulley with securing screws and a >knurled section which would be inside the pulley.. Now it >was just a case of filling the recess with the thermoplastic >- dunk the plastic beads in very hot water until they turn >transparent and coagulate into a lump - fish the lump out >and knead it in your fingers to get the trapped water out, >then press it into the mold like plasticene forcing it first >into the teeth of the belt with something like a screwdriver >blade, then filling the centre. This is much easier to do >than to describe!! I didn't bother with cheeks on my pulleys >and they run fine without shedding the belts but, if you >need cheeks, you can just turn up a couple of disks if thin >metal and bolt them right through the pulley - warming them >a bit first will set them flush against the sides of the >pulley. The finished thing is an exact fit to the drive belt >and is of a tough nylon consistency. This is the easiest way >I have found to make the pulleys but, if you really want a >metal one, this would also be a good first step as you could >measure from this the exact OD required and use it to gauge >a formed flycutter while you make it.. > More of that thinking outside the box. Love it, Ian. How about just pouring it full of epoxy if a release agent could be found?
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