Looks like an inverse undercuttee!

[LittleWatchShop]

What are they?

[HectorLooi]

I hv a set similar to this too. Mine has a handle included in the set.

I'm not sure if I'm using it for the intended purpose but I use it to cut down prefabricated brass bushes after pushing the bush into the plate. Especially when replacing the bush of the centre wheel.

[tomh207]

I think these would be used for hole sinks. Once the screw hole for threading is cut the pin on the cutter acts as a guide in the hole and the cutter rotated to form a recess for the screw head. I can’t seem to remember at the moment the proper name in machinist speak, getting old sucks It is not a counter sink but for recessing cheese head screws.

 

Tom

Edited January 18 by tomh207
Spolling mistakes/autocorrect

[rjenkinsgb]

12 hours ago, tomh207 said:

I can’t seem to remember at the moment the proper name in machinist speak, getting old sucks

Counterbore tools

[tomh207]

@rjenkinsgb thanks Rob, I should go and write that down somewhere

 

Tom