Making gears outside of the recommended range for the cutter

[DeereGuy]

Hey gang, anyone ever try to cut gears that were not in the recommended range stamped on the cutter. My cutter is for 26 to 34 teeth and I need to cut a gear that is 21 teeth and one that is 42 teeth. I know that I can buy the correct cutter if I have to. This application is for hand cranking and not high speed.
Any thoughts or experiences will be appreciated.

TIA.

Bob

[Evan]

That should work fine as long as you use the same cutter for both gears. It will be slightly rougher and noisier as it won't have the correct involute profile for either gear but for hand cranked gears this isn't a big issue.

[DeereGuy]

Evan thanks for feed back. Now I just need to figure how to build an expanding mandrel for turning between centers. Have you done anything like this?

[dicks42000]

Check out Tubal Cain's book, "Work Holding in the Lathe" for a discussion of mandrels: expanding, taper & otherwise. Also the Atlas lathe handbook "Lathe Operation etc" has a brief intro. to mandrels, as does "The Amature's Lathe"
Hope that helps.

[Evan]

If you mean making gears, then yes. If you mean using an expanding mandrel between centers then no. A taper mandrel is probably more accurate and easier to make. How do you plan on indexing the gear blank?

[DeereGuy]

****s4200, thanks for the book reference. Sounds like something I need to add to my collection. You can never have to many reference books.

Evan, sounds like the tapered mandrel is what I need. I spent some time in the shop yesterday evening deciding lengths for the mandrel and what taper I should use. I think I will need to make two so far. One for a .5 diameter bore in the gear and one for .375. A good project for the weekend.

I am using a dividing head with tail stock on my mill. I now have a gear cutter that got off ebay and built an arbor for it. Actually what I did was take a slitting saw arbor I had built for a 1” bore. The bore on the gear cutter was 7/8 so I made a spacer and new end so I can use it for both. I have already cut a couple of gears using a boring head holding a hand grinded single point cutter. The gears turned out ok for my first time I guess. I held those using the 3 jaw chuck on my dividing head and a .5 dia bolt with a sleeve and then a locking nut to hold everything tight. Naturally the fit was pretty loose so the gears are less than concentric.

Thanks…Bob

[neonman]

I did this once by accident, ( i forgot to change the cutter) the gears were about 32t & 64t. So the cutters were more than 1 size off. The bottom line is the gears didn't play nice together. I had to do it right.

neonman

[JCHannum]

The gears will be kind of close, and will kind of work. They may be acceptable for your application, but some adjustments will have to be made to get them to function. The center distance will probably need adjustment for operation and gear life will be shortened.

For arbors for gear cutting, stub mandrels with the gear blank held solidly in place with a bolt are the best choice.

A tapered arbor is OK for turning and light machining such as grinding. If used for gear cutting, there is a good chance it will loosen and the gear blank will slip. This usually happens when the next to last gear tooth is being cut.

[Evan]

This usually happens when the next to last gear tooth is being cut.

That sounds like the voice of experience.

What I would use is a tapered mandrel with a portion threaded on the skinny end. Then an appropriate length sleeve can be placed to hold the blank on the taper snugly and held with a nut on the mandrel.

[DeereGuy]

I did this once by accident, ( i forgot to change the cutter) the gears were about 32t & 64t. So the cutters were more than 1 size off. The bottom line is the gears didn't play nice together. I had to do it right.

neonman

neonman, what was your application for these gears? Were they run with power or just hand cranked?