After I figured out the secret of how to make external wood threads [use maple and soak in mineral oil for 7 days before threading], I made some wood bolts and nuts and posted them on the Lumberjocks web page. I said there that I would just let the grandkids play with them.
A gentleman replied that he puts in a little clock face in the top of the bolt head and charges $25 for them as desk ornament. I asked him where he bought such small clocks and he told me. I bought 2 clocks to try his method out.
Once I knew the ID and OD of the micro clocks, I could check in Sketchup and see if they would the 3/4" bolt heads I had already designed. These bolt heads and nuts followed the standard guideline for steel bolts, so they look similar.
I found the clock would not fit the standard designed bolt with 1-3/8" across the flats. I had to increase the bolt head and nut size to 1-1/2" across the flats, not a whole lot different than the standard dimensions.
The Lumberjocks guy's photo looks like he makes the bolt head slightly larger than the nut. I wanted my nut and bolt head to be the same size........so I made some new nuts and bolt heads.
When I made my first maple wood nuts, I got quite a bit of tear-out on top, and some on the bottom. The 1/8" roundover router bit did not prevent or fix the tear-out.
This time, I decided to drill and tap a standard 3/4" thick maple board, then plane both sides down from 3/4" to 5/8" thick.........and remove most of the tear-out. This method worked pretty well.........except there is not much material left in the head when you drill the clock hole 3/16" deep, plus you need to drill the other side 3/4" inch for the bolt shaft to fit into. I got it to work, but you have to measure close. After I drilled the clock hole, I drilled through with an 1/8" bit, so I knew where to drill the 3/4" hole in the other side.
I finally figured out that I had not drilled the clock hole deep enough. I drilled it a smidge deeper......tested the depth with the plastic ring removed on the clock, put on the plastic ring, and it seated fine :)
The little clock has a u-shaped plastic piece under the stem, which you have to remove with needlenose pliers. Push the step up, set the time, then push stem back down, just like a larger clock.
I just used Mineral Oil as the finish. I wiped the excess off with a rag, then dried in oven for 15 minutes at 120F.
I got the little clock in the larger bolt head :)
Some future experiments to run if I make more of these........
1. Increase nut and bolt thickness to 3/4" versus 5/8". Gives more depth for bolt head where you drill one side for the clock and the other side for the bolt shaft.
Experiment with using larger round-over bit before tapping to reduce tear-out and need for planing away tear-out
2. Try staining maple to walnut or cherry color. I'm not sure how the mineral oil soaked bolt shaft will absorb stain after the threads are cut. Might have to clean in
turpentine to remove mineral oil so stain will take.