Bridgeport Mill – Power feed Gear Teeth Repair

I have an original power feed on my Bridgeport Milling machine. Two of the gears in this transmission have broken teeth, and I decided to try and repair them. Here are the gears in question:

After cleaning up the gap a little, I brazed a big glob between the existing teeth. Yeah, first time brazing.

Then, after everything settled down, I stuck in the milling machine and cleaned up the edges a little with an endmill.

My plan for the cutting was to install a right-angle adapter on my mill, along with my rotary table. Then mount a round bar in the center of the rotary table. I cut it down to fit each gear, then threaded a hole in the top for a bolt, and milled a keyway to hold the gear in place. Here’s the setup (photo actually taken after the cutting):

I found the gear cutter in among a bunch of gear cutters that I’d bought at a machine shop auction. It’s not the right size, but it feels very close when I test-fit it on the gears. I don’t really know how much effect it will have when I cutting with the mill under power feed. I know that gear cutter selection is very specific (diametral pitch, pressure angle, etc.) and not so loosey-goosey. I’m going loosey-goosey on this.

So, up first, I’m going to install a gear, and make some preliminary cuts with a saw blade, in-between the new teeth. Then I’ll change to the gear cutter and go back in for a tooth-shaped cut. I’ve never cut gear teeth, and have no idea how it should be done. This may be obvious to the trained observer.

With some slots cut, I change out to the gear cutter, and line it up. I’m starting a couple of teeth before the cut, and “practicing” moving the table into the cutter on existing teeth. Then I rotate the table the proper angle, and go in to another. When I get to a new-tooth location, I power up and move in for the kill.

I think, at least, it LOOKS like legitimate gear teeth. Now to install them and check it out.


Leave a Reply

Your email address will not be published.