This is a bad design idea.
Basically you are building a coil gun that has its ammo attached.
A motor, on its side, with the chisel attached to a cam will give you the up-down strokes you want..at speed faster if you wish.
A spring return at the last 5% of the stroke will keep too much shock from the motor.
The problem with your idea, is you will need a guide to keep the chisel straight through its flight.
You cant use many metals because that will change your inductance and flux.
The motor on its side, cam, chisel.
Look up jail house tattoo gun.
You can use the exact layout, just larger parts.