On Sun, 20 Dec 2020 11:03:51 -0000, Brian G wrote:

How can that work,

Hand crank drives a rachet type mechanisum. As the crank is turned
the pawl compresses BFO spring. When the pawl drops off the rachet a
system of levers accelerates a large lump of metal that hits the end
of the drill bit. Another pawl and rachet from the hand crank rotates
the bit 1/4 turn for each blow of the "hammer".

Harry Bloomfield; "Esq." wrote in message
...
Here's one I have never heard of before, a hand cranked Rawplug
drill.
It uses the old manual hammer Rawlbits, bit in a hand cranked
hammer
drill.

https://www.youtube.com/watch?v=zTyZgOkWs4o

--
Cheers
Dave.