Gear cutter size for clockmaking

[RSG]

I've been preparing to start cutting gears for my Tourbillion project and was about to buy some involute cutters from MMC but after watching a few horology videos it appears as though clockmakers use a smaller set of cutters (dia.) which I can't seem to find anything on them.

My question: Would the cutters on MMC work for the sizes of gears I need? See below:

I need to cut gears as follows:

Wheels - 1.708" dia/60 teeth
Pinions - .208" dia/8 teeth (8 leaf)
PA - 14.5*

If I'm correct the cutter I'd buy from MMC would be: Trade#2, 48 gear pitch. MMC part #3034A823 Is this correct?

Thanks in advance

[KellyJones]

Well, let's see.
I assume the diameters listed in your post are outside diameters.
The formula for "Standard" gear proportions is that the OD = (N+2)/Pd, where Pd is the pitch of the gears. That makes your pitch 36.3 for the wheels, and 48.1 for the pinion. Not going to work. The pitch needs to be the same. (If I got it wrong, and the diameters are the pitch diameters, then the required pitch is 35.13 and 38.46, and they still won't work.)

Let's start by picking a suitable pitch. If the pitch is 48, then the OD of the wheel would be 1.2917" and the OD of the pinion would be .208 inches. For a 32 pitch gear, the ODs would be 1.9375" and .2778" respectively. I pick those two pitches because they are available on the McMaster-Carr web site.

If those pitches don;t work for you, we could try module gears to see if we can get closer to your needs, but other than space considerations, what is important is the numbers of teeth (for the clock function).

Let me know if you need any further help.

[ctwo]

I'm too cheap to buy these cutters, so I was planning on making a fly cutter for this task.

These gears are typically metric and the formula I saw this morning was for module = OD/n+2.76

I also heard that the gear cutters come in half size increments (0.55, 0.60, 0.65...), so you are looking for m 0.50 and 0.70.

https://www.csparks.com/watchmaking/Cyc ... /index.jxl

It only takes about 3 minutes to make one this way

[rmac]

Maybe this'll help??? Maybe???

http://amzn.to/2HI6ca9

[whateg0]

I thought I had read awhile back that involute heard aren't normally used in clocks and the like. I don't recall the right shapes name though

[pete]

Cycloidal is the term I think your trying to remember. Almost or are teeth with straight flanks and a radius on each side of the tooth tips. Afaik that gear tooth form isn't used on every gear though. And that's about all I know about cutting clock or watch gear teeth.

[RSG]

Thanks for the responses guys! In the interim of starting this post I have since done much more reading and learning in order to understand what I'm trying to do. It's very complex as I have come to learn.

[RSG]

Let's start by picking a suitable pitch. If the pitch is 48, then the OD of the wheel would be 1.2917" and the OD of the pinion would be .208 inches. For a 32 pitch gear, the ODs would be 1.9375" and .2778" respectively. I pick those two pitches because they are available on the McMaster-Carr web site.

If those pitches don;t work for you, we could try module gears to see if we can get closer to your needs, but other than space considerations, what is important is the numbers of teeth (for the clock function).

Let me know if you need any further help.

Thanks KellyJones!

Ya that's not going to work! Those measurements are the outside dia of the wheels and need to be very close to that measurement. Would it be better if I gave the distances between pivot centers?

[RSG]

I'm too cheap to buy these cutters, so I was planning on making a fly cutter for this task.

Thanks ctwo! While I have watched many of those click spring videos I must have missed this one. I'd be keen to try it it too but I'll need to figure out the right form to machine the tool steel to on the lathe first. Any ideas would be appreciated.

[RSG]

Cycloidal is the term I think your trying to remember. Almost or are teeth with straight flanks and a radius on each side of the tooth tips.

Thanks for the correct terminology Pete! One step closer....

[RSG]

Maybe this'll help??? Maybe???

http://amzn.to/2HI6ca9

Awesome find rmac! Thanks....I'll likely buy it

[RSG]

https://www.csparks.com/watchmaking/Cyc ... /index.jxl

What a handy tool ctwo! Thanks for that! I was able to input my numbers and then generate a DXF and import it into my drawing. It immediately told me whether my gears will work or not. And I will now cut my own cutter from the numbers I got.