Gear for a clock

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Gear for a clock

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jcs0001:
Finally got back to this project and made a gear blank on the lathe. Pretty simple lathe work so I don't have any photos. One photo of the blank beside the gear that it will (supposed to) mate with.

The blank is a bit thicker than it's mate however I can reduce this later if it is a problem. There is lots of room for it so I don't anticipate problems.

I'm still awaiting my book on gear cutting so this will be it till I can go through the book.

John.

raynerd:
John, if you are using brass bar for your blank then you should be fine as this will be some form of free cutting brass. I'd advise cutting against a good sacrificial back plate - if the brass isn't great, it'll stop the teeth bending (which shouldn't happen as it looks pretty thick) but it'll stop throwing big burrs and give you a good clean cut. I'd use aluminium if you can afford it, but ply would be better than nothing.

Based on your calculation of the known gear, OD = (N+2)xM
19.4(mm OD)/32 = 0.6 Module ??

Working backwards from that, I calculate backwards from your 1.505" blank would be 61 teeth - which isnt correct as it should be a 60 tooth gear.

Something isn't right!

jcs0001:
Raynerd

Good idea about a backing plate - I've got lots of aluminium so can easily come up with a piece to match. I'm still awaiting my gear cutting book and haven't had a lot of time to look into it otherwise. I do accept that I may have to cut more than one gear before getting something that looks like a gear and works. I hope it doesn't turn into a lifelong project (cut one gear per week trying for the right shape and size :doh:).

Any suggestions etc. are appreciated but please keep them simple as I really don't know much about gears.

John

sparky961:
Ok, this will be really simple... :) Use what works. Yup, that's it.

Sure, there are lots of different forms for gears and such, but you can usually very effectively hand-grind a tool blank and single point it. Using only a few test pieces you can refine the profile until you get something that meshes very well when you view two mating parts with strong light behind.

Of course this isn't going to work for all applications so don't go off on me about "proper" gear cutting methods. I've made a few custom timing pulleys this way, and there's a thread somewhere on here showing a bandsaw worm wheel that I cut and "ran in".

I'm not sure how critical it is in a clock, but I'd think that a bit of backlash in there wouldn't matter too much. You'd think the most important part would be to get the number of teeth right so that it keeps time properly.

So.... tell me - how naive have I just proven myself to be about clocks? ;)

raynerd:

--- Quote ---Sure, there are lots of different forms for gears and such, but you can usually very effectively hand-grind a tool blank and single point it.
--- End quote ---

Where on earth are you when I need you in my workshop! :-) I've never been able to hand grind single point cutters for clock gears. I have a friend clockmaker and he can do it.... it can be done. I'd certainly need a cut wheel to match the profile to while I cut it. I have a cheap fat grinder and I just can't get such a small intricate profile of the blank cutter even with my grinder and array of slips and stones. As they say, a poor workman always blames his tools.

Jcs0001 - I've missed what book you are waiting on arriving?

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