The escapement drops are restored by filling the wear grooves in the recoil pallet faces.
Starting from the left picture, there is quite a deep wear groove, which is not unusual. The problem caused by this wear is that the inside drop of the escapement is increased. An increased drop means less impulse — and therefore diminished pendulum amplitude — which may be enough to stop the clock from running reliably.
The next two close up pictures show the addition of material to the discharge corner of the entry pallet, to ensure there is enough material for the inside drop to be restored to what it should be. The groove has been filled and ground back and now extra material is being added to the corner.
With Microwelding there is no need to bend the pallets closer together to reduce the inside drop; extra material can be added instead.
Sometimes repairers used remove metal to remove the wear marks and then to bend the pallets closer together, in order to reduce the inside drop. Because the outside drop is also affected the backcock was dropped to compensate. This is not an acceptable repair. It risks breaking the very hard pallet frame. However, sometimes people heated the frame to temper it a little so it would be less likely to break. This was done just to get the clock out of the door more quickly and get the money in. The owner would never know, and it would become the next repairer’s problem!
A better approach to this repair is to remove material from the faces of the pallets by approximately 0.4 mm. The intention is not to remove the wear marks, but to ensure the finished level of the pallets remained the same, so leaving the original geometry of the pallets unchanged. Two pieces of mainspring of the same thickness, about 0.4 mm are then hardened and soft soldered to the faces. When these slips of steel eventually wear, they in turn can be replaced. Ultimately this can be done many times, and the original pallet frame is preserved.
Removing the metal from the dead hard pallets would be more readily done using a diamond file nowadays. But if necessary the pallet frame could be tempered to reduce its hardness. This would not affect the ultimate hardness of the repair, which depends only on the slips of steel fitted to the pallet faces. Soft soldering would not reach temperatures which would seriously reduce the hardness. However, once having refaced the pallets, if they were to wear rather more quickly than the originals, it wouldn’t really matter. They can be refaced as many times as necessary.
The least acceptable approach to this repair would be to make a new pair of pallets.