Making a New Gear

[oldgeek]

I'm designing a new gear. I have it all figured out on making it except one thing. How to put the keyway in the bore. I was going to ask about how to do that, but am not sure how to broach the subject.

 

[RonD]

There are a couple of ways

Google: how to cut internal keyways

Using a shaper or lathe is the slowest method, but works just fine, need tool with correct width cutting blade
You can get an attachment for a drill press with correct width grinding blade

So depends on what machining equipment you have access to

 

[alwaysFlOoReD]

I'm designing a new gear. I have it all figured out on making it except one thing. How to put the keyway in the bore. I was going to ask about how to do that, but am not sure how to broach the subject.

I saw what you did there...

 

[rumblecloud]

me too

 

[ericbphoto]

I saw what you did there...

So did I. So, obviously, you know you need a broach. 20 minite job once you find that and a press.

 

[don4331]

You don't need a broach, it just makes the job a lot faster.

I drilled 2 small holes in corners of what would be the keyway corners so that I would have a final reference point; then number of larger holes to remove the majority of the remaining material. A cut with the hacksaw to join the holes and some file work to smooth everything out.

And that's how I broached the subject.

 

[ericbphoto]

You don't need a broach, it just makes the job a lot faster.

I drilled 2 small holes in corners of what would be the keyway corners so that I would have a final reference point; then number of larger holes to remove the majority of the remaining material. A cut with the hacksaw to join the holes and some file work to smooth everything out.
View attachment 77873
And that's how I broached the subject.

You, sir, have an enormous amount of patience. Well done.

 

[don4331]

You, sir, have an enormous amount of patience. Well done.

My kids might disagree with that comment.

Some piece of machinery on the neighbour's farm had a lead screw with an unusual pitch (not standard metric or imperial) that failed. He wrapped a silk ribbon on a piece of rod in helix of the correct pitch, scribed that onto the rod and then proceeded to cut the screw with a hacksaw. It was about 3' long; he did it all with 1 blade for the saw, and when he finished it looked better than the factory piece.

When you learn from craftsmen like that, my level was minor.

And what hurt with my project - Blackspire came out with a 38t rear sprocket a couple years later. So, the bike has a commercial gear now, not the fancy one I made.

 

[oldgeek]

You don't need a broach, it just makes the job a lot faster.

I drilled 2 small holes in corners of what would be the keyway corners so that I would have a final reference point; then number of larger holes to remove the majority of the remaining material. A cut with the hacksaw to join the holes and some file work to smooth everything out.
View attachment 77873
And that's how I broached the subject.

With a job like that, it would take some ex-splining.