There are a number of different styles of taper harp tuning pins. I am trying to categorise them so that it is easier to be specific when talking about the different types. Up to now I have talked about the “old” style with fat drive heads, and the “modern machine-made” style with narrow heads. But I see now that these are rough categories, which can be broken down more subtly.
I think the most distinctive and diagnostic thing is the relationship between the drive and the shaft. The drive is the square- or rectangular-section end of the pin, which is where you put the tuning key on, to turn the pin. The shaft is the conical main part of the pin, which is embedded in the wood of the neck, and also which carries the string at the far end. The shaft is always, and the drive usually, tapered rather than parallel-sided.
Basically I think the first diagnostic is whether the head is wider or narrower than the shaft; in other words whether there is a step up or a step down to the head from the shaft.
I’d suggest Type 1 pins have a step up from the shaft to the head; Type 2 pins have the head about the same size as the shaft, and Type 3 pins have a step down from the shaft to the head.
We could have sub-categories; sub-type a could have a sharp step at about 90°; sub-type b could have a clear transition at about 45°; and sub-type c could have a very smooth flat transition. We could also append R for pins with rectangular (not square) drives.
Because both head and shaft taper away from the centre of the pin, and because there is often a gradual transition from shaft to head, it can be hard to state at what point the diameter or width of each part should be measured and compared. So while it is easy to think about comparing the width of the head with the width of the shaft, it is often difficult in practice to choose where to measure. So my idea of looking for the nature of the “step” between shaft and head might prove more useful.
I think that previous attempts to document tuning pins have not been specific enough about where the measurements have been taken. The scheme below suggests where to measure:
The following measurements can be taken to record a pin:
1. Distance A-B
2. Diameter at B
3. Distance A-C
4. Diameter at C
5. Distance A-D
6. Width across flats at D
7. Depth across flats at D
8. Distance A-E
9. Width across flats at E
10. Depth across flats at E
11. Distance A-F
From these measurements we can calculate the taper of the shaft, the range of sizes of tuning key socket which will fit the head, and the nearest standard taper hole that the pin will fit in. We can also work out the nearest standard taper blank to use for making a copy.