gear cutter for pocket watch sized gears

[RSG]

I am working on a project that requires cutting small gears. After going over everything I can find I still don't know if the standard involute cutters available from someone like Mc Master Carr are the same ones used for small gears like that found in a pocket watch.

I'd like to know if they use the same pressure angle and would a #1 or #2 cutter work? Anybody know?

[Bill Shields]

Depends on where the watch was made.

If it came from Switzerland (or Europe in general), the shapes are quite different than if it was made by Waltham

Nowadays, most of the parts come from China (even a large % of "Swiss Watches" have Asian parts in them.)

[RSG]

Thanks for the reply Bill!

I did some digging myself today and took some of the actual gears out of a pocket watch then headed over to my local machine shop buddies place. He has a set of those gauges. The gears I'm most interested in were 14.5 deg PA and 64 Pitch. I'll need a #2 and #8 cutter. So now that I know that I can move forward with preparing to cut my gears.

[neanderman]

@rsg, that's quite a challenge. I hope you'll share your experiences!

What watch(es) are you working on?

[RSG]

Thanks Ed,

It's actually not for a watch but for another project that will have a Tourbillon in it (google it if you've never seen one). I'm starting with a larger version to confirm everything then the next project after that will have three Tourbillons that are 4 times smaller revolving around it's axis. I'll definitely post some pics along the way.

[Bill Shields]

I have a few clients in CH that make watch parts -> a few cases their own watches start to finish.

Quite remarkably, many are still using mostly the old mechanical cutting / hobbing machines from 100 years ago, while a few of the more progressive fellows are using more and more of the computer driven machines (sliding headstock lathes, mills, jig borers and grinders).

Many of the items coming from Asia are 'stamped' as opposed to cut.

[RSG]

It's very cool to watch them do things like hand file/polish parts that are smaller than a grain of rice, not to even more delicate things like hairsprings. I find watch movements fascinating hence why I want to incorporate a complication in one of my reels. It will only be for looks of course.

[Bill Shields]

The Swiss government is on a move to crack down on 'SWISS MADE' logo because so much of the 'guts' of watches are coming from 'elsewhere' and only being partially assembled in Switzerland so that they can get the SWISS MADE logo. I think that they are going to start requiring something like 80% of all parts to be actually MADE in Switzerland....so there is a big push to train folks to run CNC machinery to actually make the part as opposed to ordering them from a catalog for $5.00 for everything (really....)

[jscarmozza]

I went through my box of gear cutters, the highest DP that I have is 48, so I can't help you out in that way. However, have you thought about making the cutters that you need? The March/April issue of HSM magazine has a very good article on making gear cutters, as does Ivan Law's book, Gears and Gear Cutting. Law provides a number of methods for making cutters, I made his version of the Eueka mechanism. I had a lot of trouble getting it to work properly, mostly because of my sloppy work in making the mechanism. That being said, it is a very tedious process making a cutter with the Eureka, but you will wind up with a nice little gear cutter about the size of a quarter, which is likely what you want. If you decide to go that route I can alert you to all of the places I went wrong when making mine. Good luck with your project, John

[RSG]

Very cool device John, just watched it on youtube. I found out that most of the gears I require can be cut using 48 and 64 pitch cutters. If I ever have to go smaller I'll definitely look into that machine and your advice.

[Wolfgang]

RSG, I can probably hob those 48 and 64 DP gears for you should all else fail. w

[RSG]

Thanks for the offer Wolfgang! I gotta try it for myself first