Hobbymat MD65 / Proxxon SD300 gears for automatic feed

thingiverse

I've got an old Hobbymat MD65 desktop lathe but the changeable gears for the automatic feed are completely missing, so I decided to design my own. Normally there is a set of single gears which can be combined onto a brass bushing, but the bushing is missing too. Since I don't want to cut threads on this machine, I decided to create just a few gears with fixed ratios only for form feed. The usual ratios on the plate at the machine are 75-20 (pitch 0.08mm) for smoothing and 75-40 (0.16mm) for rough machining. I added a ratio of 75-30 (0.12mm) to be a little more flexible and a ratio of 100-18 for super smoothing. The gears are designed for use with bearings R1810 ZZ in the dimensions 7.938 x 12.7 x 3.967 mm. My decision for this bearing was because of the tight fit on the 8mm axle at the machine. The bearing seats in the gears are designed in 12.90mm because of the tolerances of the 3D printer. I've printed the gears with the settings below and the bearings slipped into the gears nicely tight. I've got a very old Hobbymat MD65 desktop lathe but unfortunately, all changeable gears for automatic feed are missing, so I decided to design my own gears. Normally, there is a set of single gears which can be combined onto a brass bushing, but unfortunately, this bushing is also missing. Since I don't want to cut threads on this machine, I decided to create just a few gears with fixed ratios only for form feed. The usual ratios on the plate at the machine are 75-20 (pitch 0.08mm) for smoothing and 75-40 (0.16mm) for rough machining. I added a ratio of 75-30 (0.12mm) to be a little more flexible, as well as a ratio of 100-18 for super smoothing. The gears are designed for use with bearings R1810 ZZ in the dimensions 7.938 x 12.7 x 3.967 mm, chosen because they fit tightly on the 8mm axle at the machine. The bearing seats in the gears are designed to be 12.90mm due to the tolerances of the 3D printer. I've printed the gears with the specified settings and the bearings slipped into the gears nicely tight.