Best Way to Shave a 36 Tooth Gear

I am trying to build a type of transmission. I have the concept built and it works, but I would like to get the shifting a little smoother. I was hoping to do this by shaving the edges of my HS 36 tooth gear off. I have seen other teams do this in previous years. What is the best way to do this? Have teams that have done this used special machinery? I have means of cutting them off, but I am just worried that a grinder or band saw cut is going to cause more friction than I desire.

I would use a lathe, if you have access to one. That has produced the best results I have seen.

Like this?
That was done with a belt sander. Or if you want to sand each individual tooth to make it pointy, I don’t know of any tool other than just filing each one, although I don’t know how much that would really help for the time and effort.

We put the gear on an axle in a drill and ran that on a belt sander while spinning the drill to make our transmission gears last year. I imagine a drill and sandpaper would work just as well if you don’t have access to a belt sander.

I do not have a belt sander, but I do have a small bench grinder. I might just have to use that and file it afterwards. Then just grease it.

I’m not sure a grinder will work very well. Most grinding wheels will somewhat melt and make a mush of plastic. Also, plastic might end up embedded inside the grinding wheel grains. It’s one of the reasons why you should avoid grinding soft aluminum, too - it just mushes into the wheel.

We did ours last year with a grinder…turned out just like the ones picture in the above posts. Just have to take it slow while grinding to prevent overheating.

If I had to do it without using a lathe (which I would say is the “best way”) I would stick a close-fitting bolt through the square hole and tighten it with a washer and nut, then chuck the bolt into an electric drill so I could spin it against a piece of sandpaper (or against the spinning belt sander or grinding wheel) and get a uniform chamfer all the way around.

Here’s some advice (from experience) on a using a lathe: don’t use a piece of high-strength shaft to hold the gear, the cutting force will try to rotate the gear on the square shaft, and it splits the gear pretty easily. Using a bolt and nut as above would work, but I found the best solution was to screw the gear through all the screw holes to a sacrificial gear (and use a short piece of HS Shaft for alignment), and chuck onto the sacrificial gear so as not to damage the teeth on the gear being machined.

If you’re talking about shaving teeth (or parts of teeth) off, like a slip gear, I used a dremel to shave off the teeth for my slip gear last season. Perhaps it would work on corners too.

If you need precision, then I’m not sure you could get the fine control needed with a hand-held dremel though.

We have used a file in the past to make teeth smaller, and to make them disappear completely. I suggest that if you are in fact making the gears smaller, to use a small nail file for precision, so that you do not ruin any gears. (Glass nail files work the best for both nails and gears.)

Run the drive with the gear on it and use a file. Alternatively, put the gear in a drill and use a file.

A lathe will not work if looking to shave off only a few teeth (slip gear). If you’re looking for the absolute best and most precise way, a CNC Mill is going to be your best bet. You can do an arc path, program it in with the part clamped down and an end-mill will machine off what you need.

Now most teams don’t have access to this kind of machinery. If you do not, or cannot find a company willing to let you use/help you with using one of their machines, then the dremel is probably your best (really only) option.

They are trying to make a transmission with these gears though, not slip gears. The lathe will work quite nicely