Joe's 1000x600x200 steel and aluminium router started

[devmonkey]

'Great minds' and all that.

Yesterday I used the CamBam trochoidal pocket plugin to cut out the teeth for a ratchet made from Jarrah hardwood. Conventional shallow cuts tend to take the corners off the teeth where the grain is tangential to the wheel so being able to do a 12mm depth of cut with a 2mm diameter tool is a bonus. I still had to redraw the original ratchet design (produced in Gearotic which will also draw HTD and many other pulleys for you) with rounded teeth to avoid some chipping. This cut used a two-flute straight cutter with a speed of 1000mm/min and a stepover of 0.15 (0.3mm) and the maximum 24000 rpm. This took about 25 minutes for the 110mm diameter wheel.

Very nice Kit! This was the first time I'd used trochoidal clearing, definitely a keeper for thin endmills in metal.

Now I have a question for you pulley experts. I need to make a very large 157 tooth 8m timing pulley ring that will be fitted to the perimeter of a winch drum. The pulley needs to be made of a ring of material ~25mm thick with an outer diameter of 400mm and inner of 340mm. It could be made from aluminium, SRBP, delrin or even hdpe.

Trouble is I don't want to waste a large piece of material just to make the ring, any ideas? I've even considered casting a blank in aluminium but I don't have a foundry. Are there any castable machineable urethanes that are strong enough for timing belt pulley teeth?