Center drill options

I work field service machine tool repair.
I carry center drills and 1/8 HSS Drills.
If I am trying to remove a broken pin,shaft or bolt I start with a center drill then go to the 1/ 8 drill.
If I can get a hole in it I can get it from there.
Point is a sharp HSS center drill is a great cutting tool.
 
Centre drills are for centres and spotting drills are for starting holes.
If centre drills were better for starting holes then there would be no need to make spotting drills.
 
I started my first machining job in 1978, I remember spotting tools were marketed and sold under the name NC SPOTTING TOOL.. the shop engineer told me it was because the lack of feel, the NC machine
Couldn't come out and feel the tip touch and start to drill.
That company we made tooling for the machining industry.
Center drills have been the go to for starting tools holes well before spotting tools came along.
To this day when I work at some old shops, you can find center drills with 1 1/2 and 2 inch bodies!
 
sdelivery said:
Center drills have been the go to for starting tools holes well before spotting tools came along.
To this day when I work at some old shops, you can find center drills with 1 1/2 and 2 inch bodies!
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I also think centre drills were before spotting drills & I expect there were other methods before centre drills. Things progress and spotting drills are now regarded as the best method to start a hole.
I'm not sure what is the largest size centre drill, there must be some very large ones for supporting heavy shafts on a lathe.
 
mikey said:
I prefer to use a spotting drill myself. The correct spotter depends on the drill geometry of the drills you use. If you use 118 degree drills, use a 120 degree spotter; for 135 degree split points, use a 140 degree spotter.

While you can use center drills for starting holes, spotters are more accurate in my experience. We had a great discussion on spotting drills in this thread.
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Mikey couldn't have explained it better.
 
i can occasionally see a center drill "wobble" around on the surface of the stock in the lathe. started using spotting ;;drills and that issue went away. like david said above ; center drills were not designed for what guys use them for in the lathe
 
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