Making Gears

• Cutting the first set of gears with the indexer. The gears are 15 teeth at 48TPI pitch. They are to be mounted on small stepper motors for driving instruments. Now that I've finally cut the first gears with the cutters, I'm not especially pleased with the tooth profile the cutter gives. The gap between the teeth looks too big and the tooth shape doesn't look like right. On the next set, I'll try the next numbered cutter which should have a smaller profile.

• It turns out that the problem was a faulty cutter wheel. The cutter had the wrong profile compared to the ones either side of it in the set. The one in the middle is the culprit. If you look closely, you can see that the part that cuts between the teeth is thicker on that cutter than the ones either side of it. A replacement is on the way.

• Success at last. Using the cutter for 12-13 teeth, I tried some 12 tooth gears. Again the first batch didn't turn out, but that was my fault. The second batch are perfectly formed and look identical to a commercially made gear, except it's made from nylon and mine are aluminium. The second pic shows their intended destination, mounted on the little steppers I bought (cheap!)

• I've devised a system for making larger gears. The gears will be made from sheet metal. The blanks will be bolted to a faceplate that can be mounted on an arbor on the lathe. Then when the blank is turned to the correct size, the faceplate with the blanks attached can be unscrewed from the arbor on the lathe and screwed onto the arbor on the mill so that the teeth can be cut. The two arbors will remain setup for the duration of the gear making process. Having two arbors means I don't have to keep setting up the alignments. I will make different size faceplates to suit the size gear I need to make.

• The gear making operation is becoming quite successful. I made three 64 tooth gears for the altimeter. Each gear will drive one of the pointers (10s, 100s and 1000s). I made the gears from 1.6mm thick sheet aluminium. They will have brass hubs as soon as I make them. The hubs will have a flange that allows the hub to be attached to the gear by flaring (riveting) the flange over the gear. Then the hubs will be soldered to the pointer shafts.

• This faceplate is for a 60 tooth gear. The arbors that it mounts on will work for any gears from 63 teeth down to 40 teeth. I always make two arbors, one for the lathe and one for the mill.