Quote Originally Posted by ductape View Post
Internal and external gear teeth have very slightly different profiles, so it depends on the application. The planetary gears in an automatic transmission would require the proper cutters for each set. Something that doesn't need that kind of speed and torque could probably get by with just using a regular involute cutter for both.
There are some good folks here with far more machining experience who could explain it better.
Those are just off the shelf gear cutters. I have a box of them in my shop, probably those exact ones by the look of it. If you could find the proper cutter for the right tooth profile I'm sure it would work, but I don't really see a reason to use this tool to do external gear teeth. You can just use the regular old end mill arbor to do the external threads. The beauty of this tool is you can get inside of a bore, which is pretty cool. I bet you could cut keyways with this as well.