[RCP57]

This could be totally wrong but it worked on my Bruder dozer conversions. I took the chain pitch in my case- 0.375 and times it by the number of teeth I wanted. This number gives you circumference. Divide that by pi (3.14) which gives you diameter. Then divide this number in half which gives you(radius) the distance from center in which you need to cut the teeth. Divide 360 by the number of teeth and that's how many degrees apart they need to be. Use an end mill or drill bit to pop in the appropriate amount of teeth. For me making regular sprockets I then go back over them with a slightly larger cutter moved outward on the teeth. This gives the tips more angle to clear as the chain moves on and off of them. Clean them up a bit with a file and I'm good to go. It should be noted that your disc of metal needs to be slightly larger than your intended pitch circle for this to work. Hope this works if nothing else makes sense.