In recent years there has been a lot of talk about pivot burnishing. This is a skill of using an oiled, hardened polishing lap (burnisher) to resurface and render the pivot operating surface bright, flat, smooth, and toughened. Note the reference here is to “toughen,” as the process will not harden the pivot but toughens the working surface and renders it longer lasting, more resistant to wear over time, and, most important, it causes the oils used in normal operation to stay at the point of pivot contact with the bearing hole. Older techniques using powders, files, etc., along with buff sticks and diamantine, too often left residues that can get into the new, cleaned bearing surface if extreme care is NOT used. After they are burnished, the finished pivots need a quick rinse, and they and their wheels are ready for service. What is the standard of workmanship expected in the service of clocks? Pivot Y and Z are NOT acceptable. Pivot X is the minimum accepted quality, and pivot W shows the desired result to achieve EVERY time you burnish a pivot. The pivots below were all done with an oiled, carbide burnisher, then followed by the use of an oiled high-speed steel burnisher. The carbide burnisher was prepared with a coarse diamond lap on one side and an extra fine lap on the other. The high speed burnisher (the second lap) was surfaced with fine emery cloth on one side, then crocus cloth to finish the other side. When mastered, it takes about 20–30 minutes for a successful bench person to complete a set of an American time/strike mantel-movement pivots.
