Eureka relief tool – making gear/clock wheel cutters
There are now a few methods of successful and less successful gear or clock wheel cutting that I’ve attempted and documented on this website. I have never really been happy with any of the methods show. I read about the Eureka tool in Ivan Laws Workshop series book. The device allows you to put relief onto multi tooth gear cutters. Although I do try and make all my tools due to time restrictions, I advertise if anyone had one for sale. I had two replies and went with the cheaper offer, Unfortunately this turned out to be the wrong move as the tool was very poorly made and really not functional. After many hours of re-making various parts and correcting numerous mistakes I finally had a working tool.
This picture shows the parts:
The tool is incredible! A number of eccentrics and a ratchet wheel turn a blank cutter in an eccentric motion, 1/12 of a turn per one revolution of the chuck. This eccentric movement allows the relief to be put on the cutter using a standard “button” type profiling tool.
This is a cutter of 0.6 module of cycloidal clock wheel form for my latest clock. This a 12 tooth wheel cutter and will be cutting brass only. Consequently I have been told from a reliable source that cutting only brass, this tool will be fine made from case hardened steel. My next cutter will have to be made from O1 tool steel to cut steel pinions. Future cutters will all be made from O1 but for this first one, I wanted something a little easier to cut for testing the eureka.
The picture below shows the steel blank mounted on a mandrel with 12 x 4mm holes drilled as near to the edge as possible. The wheel is then turned down in the lathe to expose the holes. These holes become the back relief and gap between teeth.
Finally the finished cutter, with relief!