The top bush has an outer diameter of 12mm and a shank diameter of 10mm. Meaning a flange of 1mm.
On the request of luthiers, these bushes are supplied as standard with 2 cylindrical grooves on the smooth fitting shank diameter (see image below). These are to be bonded into the headstock (usually with a cyanoacrylate adhesive), the grooves offering extra bonding location. Splined bushes are also available but be aware that the splined bushes can cause the surface lacquer of the headstock to crack or craze. This is why the smooth diameter bushes are our standard option.
The top bushes should be bonded to the headstock. They have an inner delrin bush which is a close fit to the roller and makes for a smooth and wear-free action. Once bonded, locate the set on the headstock and mark the woodscrew holes accurately. Then pilot drill the holes 1.5mm diameter by 5mm deep. It is important that this is done accurately as poor fitting will affect the precision of the gearing and performance of the tuner.
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Examples of various sets with Recon Jet Quartz. The Quartz give the buttons a subtle glitter as they are rotated.