Why and how does a drill hammer go half the rpm when put in reverse?

Question

Why and how does a drill hammer go half the rpm when put in reverse?

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Answer 1

Because motor coils are inductors, it takes a bit of time for the field to build up. Thus, for high-speed use in one direction, you can bias the position at which the commutation happens with respect to the magnetic field. If the commutation leads a bit, the motor will generate more torque for the motor current, and it’ll go faster — in that direction.

I believe they are called brush timings. It is controlled by angling the brushes. Since drills usually operate primarily in forward direction it makes sense to optimize torque in that direction