- Joined
- Feb 8, 2006
- Messages
- 429
I have used a Tapmatic both on a manual milling machine and a CNC machining center. It does work well in both cases. Just be sure to program in a little extra Z retract if you're using a CNC. Don't ask me how I know that.
Thanks David. The cranks were machined on a machining center with a large Troyke rotary axis riding on the table. I wrote a parametric program, and it would make whatever length crank was needed. It would do right or left, with the simultaneous curve, taper, and twist shape. It engraved the length and date automatically. It was a trick to do the scaling because the stuff at the ends had to stay the same, so the part in the middle had to vary by a changing scale factor on the twist, taper, and curve as it approached the ends. I used a single thread mill to do the outside threads for holding the spider, internal left or right hand threads for the pedals, and fine threads for the dust cap. The left crank was completely different from the right crank in that it twisted the opposite way, had different pedal threads, and had a different end at the bottom bracket side. Needless to say, the program was pretty tough to write all by hand. They started from 2" diameter solid 7075 aluminum. The first roughing cuts were done with a 1 1/4" endmill and would shake the building.
They took a lot of hand finishing to get to mirror finish. I was pretty proud of those cranks.
Thanks David. The cranks were machined on a machining center with a large Troyke rotary axis riding on the table. I wrote a parametric program, and it would make whatever length crank was needed. It would do right or left, with the simultaneous curve, taper, and twist shape. It engraved the length and date automatically. It was a trick to do the scaling because the stuff at the ends had to stay the same, so the part in the middle had to vary by a changing scale factor on the twist, taper, and curve as it approached the ends. I used a single thread mill to do the outside threads for holding the spider, internal left or right hand threads for the pedals, and fine threads for the dust cap. The left crank was completely different from the right crank in that it twisted the opposite way, had different pedal threads, and had a different end at the bottom bracket side. Needless to say, the program was pretty tough to write all by hand. They started from 2" diameter solid 7075 aluminum. The first roughing cuts were done with a 1 1/4" endmill and would shake the building.
They took a lot of hand finishing to get to mirror finish. I was pretty proud of those cranks.