[sdiy] What is the name of this tool?

[mrmike]

Actually, if you have a center drill you can use a normal bit to finish 
the hole. It's standard in machine work, especially on lathes, to use a 
center drill to start an accurate hole, and then a normal twist bit to 
get to size.

Center drills are not step drills, it is a special drill bit with a very 
fine point and a large clearance designed to dimple metal at the proper 
angle so that a normal twist bit will not wander. I have not seen them 
at Home Despair, but they are inexpensive at Harbor Freight, Enco, and 
the like. Get the proper one for the drill bit type you intend to use.

mrmike

John Mahoney wrote:
> At 10:29 AM 11/21/2006, Louis van Dompselaar wrote:
>> I was wondering: can stepped drills actually drill the initial
>> hole or do you need to pre-drill those with something else?
>> As I see some of them have a flat tip...
>
> A flat tip suggests to me -- strongly -- that a pilot hole is required.
>
> I was taught to use a centerpunch to make a dent when drilling into 
> metal. But, I can see where that might not be good if you are using a 
> drill press and the piece is clamped down, because you don't want the 
> bit to bend. (Is there a machinist, here?)
> -- 
> john
>