Involute gear clock


Michael McIntyre
H-M Lifetime Diamond Member
Mar 2, 2018
I still haven't cut a gear yet, but I'm getting closer. I'm just making a random 18-tooth DP16 gear that isn't meant for anything. You have to start somewhere, right? It is my earnest intent to do it right the first time. I went with the 18-tooth so I could use the front plate on the dividing head the first time out. The blank should be 1.250" and I turned it to 1.248", which should surely be close enough for my purposes.


I don't have or want to buy an arbor press, so I thought I'd try this setup and see how it works. I made a split arbor out of 1/2" drill rod, sized to reach across my mill vise. It's threaded 1/4"-20, and the bit without threads is dead on 0.250", verified by three different mics. I was proud of that! I dialed it in the last hair with a file. The mating side is reamed to provide enough clearance to screw the rod entirely together, and it fits almost flush. I didn't measure the error. I can barely feel it with my thumbnail. I don't have any short #7 or C drill bits, and these long jobber length bits really wanted to wander; even with a good center drill start. I mean it is what it is. It may not be that good in the scheme of things, but it's some of my very best work.


So anyway, the way this setup is supposed to work, the blanks are drilled C and then reamed 1/4". The blank won't fit on the arbor using hand pressure alone, so a few gentle taps. Screw the mating end on, and use the hexes to snug it all down tight. I haven't gotten so far as to fire up the gear cutter yet, but I'm hoping my setup will have enough grip to keep the blank secure.

I just barely have enough room to work around the vise, and this setup isn't going to allow me to cut gears over about 60 teeth, due to Y-axis limitations. It may not work well with all that stick out. It may be a dumb idea. Who knows. It was a fun few days making the split arbor, and setting all this up.


Tomorrow, I set about the painstaking process of dialing in my setup, and I'm going to have to use the dials, as I don't have DRO yet. Once I have a viable gear, I'll make another one a different size.

That pretty much concludes my involute gear clock build, sorry to say. One thing I've figured out from getting my hands on this is that I'm not going to have enough room to cut the higher tooth count gears. The point of using involute gears was both to see if I could do it and to use commercial cutters, but cheap Chinese cutters only come in a handful of sizes. If I'm going to pay $900 for a set of cutters, well, yeah, okay, I guess I will go with centuries of horological tradition after all, and just make fly cutters using plans from a book.

That is, in fact, what I'm planning. Building a clock from a blank sheet was just more of a thing than I could manage, so book to the rescue. I think I can build the clock in the book. It's a lot less complicated than the one Clickspring built. I mean, I didn't really want to spend three years hand filing and polishing metal anyway, to be honest. I just want a clock. That's why I'm spending $500 in tooling and probably another $300 in materials to build a clock similar to the one Hermle sells running for only $124. Machinist math!
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