Drilling a hole made with a center drill

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dml66
Posts: 41
Joined: Fri Apr 29, 2022 8:21 am
Location: SW Washington State, Steelhead Country

Drilling a hole made with a center drill

Post by dml66 »

Just wondering, if I have a center drilled hole, made by a center drill for turning, what's the best way to now drill a concentric hole? I ask because the included angle of a center drilled hole, while great for turning, may not be the best start for a twist drill.
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Bill Shields
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Re: Drilling a hole made with a center drill

Post by Bill Shields »

Do not worry about it...
Too many things going on to bother listing them.
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Harold_V
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Re: Drilling a hole made with a center drill

Post by Harold_V »

The debate of the angle of a center drill not being the same as that of a twist drill, thus not providing the needed service of starting a drill on proper location is baseless. A twist drill will follow the path of least resistance and cut size so long as the web isn't restricting cutting, which it does unless the drill has a split point, and the drill is not sharpened off center.

I started in the trade in 1957. Never in the succeeding ten years did I ever lay eyes on a starter drill. In all places where I was employed, center drills were used for starting holes on location. They used them because they work. Plain and simple. It is my opinion that the use of starter drills was more to do with CNC operations than anything else.

Like Bill said, don't worry about it. There are far more important things that you can spend your time on.

H
Wise people talk because they have something to say. Fools talk because they have to say something.
dml66
Posts: 41
Joined: Fri Apr 29, 2022 8:21 am
Location: SW Washington State, Steelhead Country

Re: Drilling a hole made with a center drill

Post by dml66 »

Thanks for the responses.

I will say that on my drill press, I've found 120 degree spotting drills give my twist drills a better start. Better in this case means imperceptible deflection and chatter. Are the holes started that way any better than center drilled ones? I really can't say, and I'm not going to waste anymore time fiddling with it 👍.
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