[How-To] Rank beginner question on cutting gears

[WobblyHand]

I've seen some plastic gear sets for slowing down the feed rate of mini-lathes for sale. They aren't too expensive, but they seem to be 3D printed, which makes me feel uncomfortable. So I am thinking about making as set myself. Down the rabbit hole I go.

So I spent a little time reading about gears. Found and downloaded some of the resources here on HM, and in this sub-forum. LMS says the module as 1, so it's metric. No surprise there. The gear set is 80/15 and 90. I can calculate the blank sizes. At some point, I will figure out the pitch angle. It's probably 20 degrees, but I'll check.

What I am confused about is when I go to eBay and look for involute cutters, they sell sets of M1 cutters. Then there are sizes of #1-8. What are these sizes? Can someone explain this?

Could I make these gears using my PM25? I probably would make the gears out of steel. What "stuff" would I need to do this? An indexing head with dividing plate, and ? Obviously, I'd have to make the arbor for the cutters, and something (an expanding mandrel?) to hold the gear blank. As you can tell, I'm in over my head, but I am intrigued with the idea of making gears. Gears have always fascinated me.

Anyways, are there resources for the dummy's guide to cutting gears?

 

[RJSakowski]

The numbers 1- 8 refer to the range of diameter gears that can be cut with a specific cutter. Yhe tooth profile varies with diameter. It is my understanding that the Asian cutter convention is numbered opposite from US made cutters.

 

[WobblyHand]

@RJSakowski, I don't know the convention for US cutters either, so for Module1 is #1 bigger or smaller than #8? Actually my experience is so limited in machining, I don't even know how to ask the right sorts of questions.

For an 8 piece set, #1-#8, M1, I can cut over what range of teeth per gear? Where can this sort of information be found? I don't even know where to look.

 

[WobblyHand]

Looked in the Toolmex catalog. #1 is the smallest # of teeth. Seems to be 12 teeth is the minimum. #8 is for the biggest #of teeth. 135 teeth. Well, that covers a decent span.

Back to what is needed to actually cut gears. How does one hold a larger M1 gear rigidly enough? The shaft ID is quite small relative to the size of the blank for 90 teeth.

 

[benmychree]

The #8 cutter will cut teeth from 135 teeth to rack teeth. An expanding arbor would not hold a gear rigidly enough and might rattle loose in the process of cutting teeth, I would use a nut mandrel with a shoulder, held between centers, a large precisely made washer to back up the gear blank would take care of the rigidity issue.

 

[Larry$]

I'm no expert either but have cut a few gears. Sets with 1 to 8 will cut all the spur gears you are likely to encounter. Do you have a Machinery Handbook? Gear cutting is explained pretty well. Module and Diametral are just two different ways of measuring (metric and imperial.) There seem to be only 3 different pitches in common use, with 20 most common. For a mini lathe I'd be inclined to use acetal, at least to start. Machines much easier than steel and is pretty tough. I made an aluminum change gear for a 10" lathe (not mine) a couple of years ago. Still running fine.

What method of indexing do you have? I have a rotary H/V table with indexing plates and a tailstock. I used the Machinery Handbook to learn how to use the indexing plates. Expanding arbors would be nice. I just offset the tailstock and turned a piece of mystery metal. I ended up buying a broach set after doing several keyways the hard way. Broaching is so much faster and easier but you need a press. Do you see the rabbit hole?

A fun project but as usual I screwed up several in the process. There are YouTube videos that help. Check out Mr. Pete & Keith Rucker.
That large gear is going to be harder to hold. Benmychree has some suggestions.

 

[Lo-Fi]

These are good places to start.

Metric gears are not well served by the readily available textbooks, sadly.

This, however, is an excellent resource:

Gear Knowledge | KHK Gear Manufacturer

Gear Knowledge can be downloaded from KHK, which includes detailed technical information with a Q & A section covering a wide range of topics.

khkgears.net

 

[WobblyHand]

The #8 cutter will cut teeth from 135 teeth to rack teeth. An expanding arbor would not hold a gear rigidly enough and might rattle loose in the process of cutting teeth, I would use a nut mandrel with a shoulder, held between centers, a large precisely made washer to back up the gear blank would take care of the rigidity issue.

Thanks, that is very helpful. I think I will make a sketch of the mandrel and post it for feedback.

 

[WobblyHand]

I'm no expert either but have cut a few gears. Sets with 1 to 8 will cut all the spur gears you are likely to encounter. Do you have a Machinery Handbook? Gear cutting is explained pretty well. Module and Diametral are just two different ways of measuring (metric and imperial.) There seem to be only 3 different pitches in common use, with 20 most common. For a mini lathe I'd be inclined to use acetal, at least to start. Machines much easier than steel and is pretty tough. I made an aluminum change gear for a 10" lathe (not mine) a couple of years ago. Still running fine.

What method of indexing do you have? I have a rotary H/V table with indexing plates and a tailstock. I used the Machinery Handbook to learn how to use the indexing plates. Expanding arbors would be nice. I just offset the tailstock and turned a piece of mystery metal. I ended up buying a broach set after doing several keyways the hard way. Broaching is so much faster and easier but you need a press. Do you see the rabbit hole?

A fun project but as usual I screwed up several in the process. There are YouTube videos that help. Check out Mr. Pete & Keith Rucker.
That large gear is going to be harder to hold. Benmychree has some suggestions.

Hah, hah, that hole is deep! Acetal might be good to start with. I have made a few acetal pieces in a lathe before. I might have some 7075 I could use, it's not round, but it is big enough. My lathe will make it round.

I have practically nothing for indexing, save for a 5C spin indexer. Don't think that will work. But you have to start somewhere. If I need to get some stuff, I will. If possible, I'd like to get something that's versatile. Don't have a rotary table, would like a small one. I have a PM25, so I can't get a big one anyways.

Oh boy, I know all about manually cutting key ways in a lathe. It's hard, especially with steel in a mini-lathe. It took me a long time, especially since the key way was blind. Yeah, the rabbit hole leads to profuse spending... But, hey, I could use an arbor press, right? Between us, I'd rather spend the cash on a rotary table setup.

 

[Cadillac]

This old Tony has a video of making the exact gears in question. He explains the difference in the 1-8 and how it’s backwards. He makes his out of aluminum good watch as always with him.