Atlas Gears

Atlas m6-101-40 gear. The large center hole is to accommodate a bearing on which the gear rides.

The Atlas Press company manufactured all sorts of home machine shop tools from about the 40s to the 70s. There are a lot of them out there, and they are by all means fairly capable machines even today. However, being old and no longer manufactured does come with it's share of disadvantages - there are few replacement parts available.

Especially when it comes to gears. For the lathe, threading was done by setting up a train of different gears to get the carriage lead screw to turn at the right rate. Our MFC mill uses these change gears (ones for a 6 inch lathe) for it's own internal gearing for the feedrate selector.

The worst part about these gears is that they aren't made out of a normal material, instead, they are made out of die cast zinc. I guess this is because they were quick and easy to manufacture (a lot of small lathes today use plastic gears for the same reason). But, after more than 50 years, some of my mill gears have worn out. One of these gears between two steel gears, and has worn into sharp edges instead of gear teeth. Also, many of these small gears don't ride on any kind of bearing, they just ride on the hole in the middle of the gear. This particular mill gear was worn in both ways. However, these gears are nonstandard and there are no modern day equivalents. But, thanks to the power of 3D printing, I'm going to try and make a replacement. Even if the replacement doesn't last near as long, I can always made another one.

I'm using the Inventor spur gear generator for this, but you can use whatever you like. For those playing along at home, the gear parameters for the Atlas 6 in lathe change gears (M6-101 series) are:

diametrical pitch - 24 
pressure angle    - 14-1/2 degree
involute teeth 

Fill in the number of teeth you want, and you will have a gear.