Tid-Bit 5 - Power Pegging
How do you clean pivot holes? I was taught to use peg wood (often tooth picks): Taper the end with a knife, then twirl the pointy end in each pivot hole. Re-sharpen when the taper was dirty (or when it broke off in one of those really small holes), and repeat until it came out of each hole clean. I have done a lot of this, but I will admit, on any hole larger than say, an eight of an inch (3 mm for those that are not metrically challenged), it took some real effort to get the holes clean. Enough effort that I have blistered my fingers pegging mechanisms. More than once actually.
So, why do we peg holes? Easy answer is because we want them clean. But, more fundamentally, I think it is important to understand a bit about what that black stuff is in the holes that we strive to remove.
Most of us are aware that the steel pinions in clocks often wear faster than the brass gears. While it is perhaps not intuitively obvious why this is so, I, for one, have seen a lot of British longcase clock mechanism with pinions that were worn significantly. The reason for this wear in clock mechanisms is, all too often, owners oiling the gears. Once oiled, any dust in the area is picked up by the oil and provides a perfect recipe for wear. The dust both suspends in the oil (wearing both the brass and the steel) and also becomes embedded in the softer of the two metals (the brass). The embedded dust no longer abrades the brass, but instead forms an abrasive surface that erodes the steel pinions.
In the same way, dust that gets into the oil around a pivot abrades both the pivot and the hole. Once the dust is embedded in the brass, it abrades the pivot. Here is a shot of a pivot from a German clock, provided by Bob Crane, that was still functional, but only just.
The goal in pegging holes is to remove the fine bits of dust and ground up metal (from the worn pivot) from the inside of the pivot hole. Given that the dust/ground metal is embedded in the walls of the pivot hole, it is important to be a bit aggressive in cleaning – hence the use of wood to mechanically abrade the hole and remove whatever abrasive materials that we can.
Which, quite naturally, brings us to the subject of this tech tid bit. I have found that nothing matches how easy it is to peg pivot holes with a tapered dowel in a wood lathe. Of course, if you don’t have a wood lathe we will have to fall back on plan B (discussed below). But, if you have a wood lathe, it is pretty easy to taper a peg to perfection with a skew chisel. And then, with the lathe doing the spinning, you can polish the inside of the largest holes, including the winding arbor holes, as well as the holes the posts pin into. Then, when the peg is dirty, use the skew chisel to cut a new face and peg again.
If you don’t have a wood workers lathe you can also use a watch makers lathe, or one of the micro machines – like the Sherlines or the Unimats. You can also use a power drill, though this will require a bit of innovation in tapering the dowels. Or you can always use a pencil sharpener to sharpen the dowels.
