First, a generous amount of string is uncoiled and a hitch pin loop is made at the free end. The loop is a set of double helix twists, in which two strands of wire wind around an imaginary central axis and not one around the other (think of DNA to get an idea of what I mean). After a dozen or so twists are made, the free end of the wire is wrapped around the base of the emerging loop with a couple of straight turns.
There are numerous ways to make these twists. Professionals do so by hand. For fun, I've been using this gadget that fishing tackle makers use to make double helix twists on wire leaders. In the fishing equipment world, this loop is called the "haywire twist".
Whatever the method, the result looks like this:
The loop is slipped over a hitch pin and the free end of the wire is guided around the appropriate bridge pin and pulled towards the wrestplank. Since the wire is kind of springy, it wants to coil back up again and make a nuisance of itself. To keep it from slipping off the bridge pin, a hemostat acts as a handy little clamp:
Note that the hemostat isn't actually clamping the wire to the bridge pin: that would cause the wire to break once it is put under tension. Instead, the hemostat presses the wire down against the bridge, acting like an extra set of helping hands.
Next, the wire is drawn about 4 inches past its final position in the wrestplank and cut free from the coil. The free end is inserted into a little hole in the tuning pin shaft, and the pin is rolled forward to make the wire wind itself on. When the tuning pin is over the correct hole in the wrestplank, the pin is hammered down into the hole with a hammer and a tuning pin setter (basically like a glorified nail set, except the notch in the bottom end is as wide as the tip of a tuning pin).
The wire, as it leaves the tuning pin and heads out towards the soundboard, must be on the right-hand side of the pin. In addition, care must be taken to ensure the wire doesn't angle downwards too severely as it leaves the nut and approaches the pin. This downbearing, if excessive, will exert an upward force on the tuning pin and try to unseat it from the wrestplank. Ideally, the wire will meet the tuning pin at right angles to the pin, which means it exerts only a forward force. The tuning pin holes were drilled leaning back at about 5 degrees to provide some resistance to this forward pull.
The best way to control the downbearing is to ensure there isn't too much excess wire to wind onto the tuning pin. The wire coils on the pin can then be spaced widely or narrowly, as needed, to control how much downbearing there will be. If there are any problems when the pin is hammered into the wrestplank, the coil spacing can be adjusted with a screwdriver tip before the pin is twisted clockwise to put the wire under tension, which freezes the coils in place.
Here are all the tuning pins with their wire coils:
Notice that there is comparatively little wire wound on the pins. The wide spiral between the upper and lower sets of coils allows me to adjust the downbearing.
Here is a view of the instrument fully strung. Note the change in sidebearing for the lowest couple of strings:
Some hitch pin loops, up close:
The hitch pins lean back a bit to resist the pull of the wire. I did this by tapping each pin with a hammer and a short piece of dowel.
With stringing completed, I examined the spacing of the string pairs at the bridge. It should be identical to that of the register slots (13.75 mm). I found a few visible discrepancies in the spacing, which also affected the sidebearing when the strings came off the bridge and headed for the hitch pins. I don't think this has anything other than a cosmetic impact, but for the sake of consistency I figured out which bridge pins were wrongly placed by using a caliper set to 13.75 mm and checking successive pairs of strings to see which one was out. Then I pulled out each wrong pin with a small vise grip, redrilled the hole correctly and installed a new bridge pin.
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