Clock Hands

I can’t seem to find anything I like to match this custom clock I’m working on. Has anyone made clock hands on their GF? Any tips on materials that worked would be greatly appreciated.

Hmm this is something that I think was discussed a long time ago. The tricky part with clock hands is that they usually need to be very thin, lightweight, and rigid, which is why metal is often used… and we obviously can’t cut metals.

How large is the clock you’re working on?

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Ponoko suggests 1mm petg, that’s actually not a bad idea.

I might try gross-grain gluing 2 layers of raw wood veneer and then cutting that. Most veneers are 1/42", so that would be about 0.04" or just over 1mm thick. The cross grain would help with rigidity. I’d be concerned about warping of the wood, though. Maybe the petg idea is best after all?

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It’s an 18” round. Thanks for the tip.

I’m sure you know about high torque movements, but in case you don’t definitely look into them. You’ll need one to drive a clock that large.

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I haven’t made clock hands with it yet, but I have made other fairly delicate moving parts with Canson watercolor artboard. Lasers like a dream, very lightweight, reasonably rigid and takes paint (or ink!) like a champ.

Might be worth a try?

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So the typical clock mechanism has almost no torque to it, so clock hands need to be super light.

You can get heavy duty torque mechanisms, though in my experience they don’t make much difference. Look for mechanisms for long hands.

There must be someone out there who makes mechanisms for very big clocks - and hence heavier hands.

You will need to find a way to fit the hands you make to the existing spindles on some old hands.

The ones I have used, the spacing between the hour and minute hands is very small, so you’ll need to make sure you have very thin material, but very rigid.

I’ve only dabbled with this, but my gut reaction is to say, buy a complete mechanism and hands that matches roughly what you want and live with that.

I have a feeling that cutting your own and getting it to work could be a lot of trouble and possible not practical.

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True high-torque movements are quite expensive and mains powered.

Battery powered “high-torque” movements are designed for super lightweight stamped metal hands, as pointed out above. There are sites “dedicated” to selling them but you can buy the same stuff from common online sellers for less. Even the more expensive ones are very sensitive to the balance of the hands, even provided ones. I have one “high-torque” continuous-sweep movement with three provided sets, and one set - which is contemporary, without the counter weight design - causes the clock to lose a couple of minutes per month. With the “traditional” hands, it’s accurate to about 10-15 seconds per month. Yeah, I’ve been tracking it because I had intended to build a clock with it. I just have the mechanism running away propped on the edge of a window ledge.

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If the hands are properly balanced not a lot of torque should be necessary? You should only need enough to move the whole mass ever so slightly?

You’d think. But even the best battery powered high torque movements need really low-mass hands. I like seiko brand and have had good luck but I use commercially produced hands.

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I was searching for “mechanical clock” on the forum and ran into this thread:

It looks to be discussing similar things; it might have some additional information?

Even in big clocks (like tower clocks) the pieces are remarkably fragile. Clocks (& watches) with mainsprings are incredibly delicate. Pendulum versions can support more mass in the movement and hands but even there, physics gets in the way. every single gear interface scrubs energy out of the system and there are simply a boatload needed to get the proper timing and sequencing of movement. Electrically powered clocks can support some additional mass but not lots more. It’s not direct gear action so the gearing losses are still present.

Relatively speaking there is not as much mass as you might think for a huge tower clock - sure they’re far thicker than the ones on the mantle, but they’re also much longer (with corresponding issues of moment of inertia) and only as thick & heavy as is needed to just keep them from bending from their own movement.

People think it shouldn’t be hard because it’s just 60rpm for the second hand, 1/60th rpm for the minutes, etc. don’t realize that to keep accuracy, the ticks are orders of magnitude faster - like 15-25,000 ticks per second. One of the things I found most interesting was the impact of gravity on clock and watch accuracy. You actually have to tune a watch in multiple positions to try to narrow the frictional losses and reduce the impact of gravitational drag on the parts. A watch movement is never as fast in all positions - you’ll always see them slower in some than others and watch timing is all about minimizing the variance and keeping it on the fast side (better to be early than late).

Not a lot of other everyday mechanisms that are measurably sensitive to gravitational fields :slight_smile:

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I ordered some plastic from this place

https://www.pickpunch.com

I don’t use it for clock hands but I would bet that it would work rather well for doing so. Guitar pick plastic can be pretty thin and I’ve cut and engraved guitar picks with the GF without any problems whatsoever.

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I would think that if you cut the hands from 1/16 maple or hickory (or even Baltic Birch) they would be lighter than metal. You could balance them with a needle through the pivot point and if necessary even add a bit of weight to bring them even. Or possible instead to find the pivot point and put the hole there. that does not get rid of the inertia issue but at least it would be balanced.

In the end, the point is not to be a chronometer anyway but to keep reasonable time and look good, if the gears are wood, temp and humidity might be the arbiters of precision far more than the hands.

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You are correct @rbtdanforth, by experience on building a wooden clock, the gears in the mechanism tend to warp with temperature and humidity.

There is a discussion on precisely this in the following topic in this forum:

Wooden clock

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