What kind of screw is it?

[A-Man_08]

How do the pins grip the screw?

 

[Isakare]

They have sharp edges and grip the ground on the screw, they are diamond studs. This bit set cost a small fortune in the 90s and wasn't sold to just anyone.

 

[A-Man_08]

Isn't that bit intended for this type of screw?
https://goo.gl/images/97ppGj

 

[Isakare]

No, it is for one-way screws that TS has. I have bought it specifically for such screws and removed hundreds with it. It is what one might call the original bit set for one-way screws.

 

[Serfi]

Thanks for all the tips! I'll have to grind a groove and then screw or find special bits.