Thru Holes In U-Drills

[Zak89]

Hey All !
So im curious i asked people around the workshop and no one has any idea my question is how do they make the U-Drills and carbine drills with through coolant holes that contour to the shape of the drill ?

 

[MikeHalloran]

I'm >guessing< that the only way you _could_ make coolant-hole drills is by drilling the holes straight, and maybe milling the flutes straight, then heating and twisting the drill, followed by hardening and finish grinding the flutes and the OD.

The part I'm guessing about is milling the flutes before twisting and hardening; many twist drills clearly have their flutes ground from the solid after hardening, and it would require just a little extra process control to grind flutes in a blank that had twisted holes inside it but no pre-existing flutes on its exterior.



Mike Halloran
Pembroke Pines, FL, USA

 

[Zak89]

yeah cool thats kinda what i was thinking but i wasent sure and thank you for your help

 

[saberblue]

Carbide drills (WC)are depending on the length extruded with the holes and flutes in the blank and then shaped (machined) in the pre sintered condition this pre sintering extracts the binder and makes the blank semi hard about like chalk -- after shaping the parts are wintered and then finished ground -- most larger diameter drills have the WC cutting portion brazed to a tool steel shank--

Many - most HSS oil hole drills are made from special drill rod that is extruded - forged - with the holes and flutes already in them..