The parts of the Lower Dials are fixed to the shaft using tapered pins.

During installation, the part is placed on the shaft, held in place, and then a hole is drilled through the part and the shaft using a taper pin drill bit.

Next, a taper pin is inserted into the hole until it stops, then it is pressed in with an arbor press. The pin is then cut or ground off.

Indicated is a hole in the Lower Dials driver gear for its taper pin.

In this dial spacer, the taper pin is clearly visible.

Rotating the shaft to the other side, we can see the over-enthusiastic application of a grinding head applied to the other end of the taper pin on the driver gear.

Meanwhile, the taper pin is again clearly visible on the dial spacer.