whats it called? drill attachment for pre-drilling

[StaticPhilly]

hello all,

ok i havnt a clue what these are called so i thought somone here might,

basiclly it drills out a ring so your screw head sits flush or in your work peace, it fits round your drill peace then tightens up.

... ok so im having trouble getting what i mean across so lets try and find a pic

like them, but, you can put your drill bit threw the middle, tighten it up so you get your pre-drill and countersink at the same time. (its just like a ring that clams to the drill bit, so the drill bit is in the chuck)
cheers,
Phil[/img]

 

[kevplumb]

countersink

http://www.screwfix.com/prods/13110...Sets/Wood-Sets/Drill-Bit-Countersink-Set-4-Pc

 

[StaticPhilly]

exacly what i was after, many thanks.

yea i thought they were called countersinks but wasnt sure if they had the same name with the drill bits in, every time i searched for countersinks i kept finding the ones i put a pic of.

thanks again,
Phil