Twist Drill Angle with Center Drills vs Spotting Drills

Actually, using just the small tip of a center drill as a spotting drill is a fairly good idea. Those center drills are massively rigid, and the 118 degree point will spot a hole for a 118 or less angle drill. You just need to make sure not to let the center drill penetrate the work beyond the angled point. It usually takes a larger center drill to be useful for this strategy.
 
Bob, that is a good strategy. I think I saw someone do it on Youtube. Big center drills can often be found used for very low prices.
 
I grind all my drills by hand and split the point on allmost all of them and if I need a spotting drill to match the drill I 'm using I grind it out of an old broken center or any old stub drill I have laying around. I bought two drill grinding machines but I am to lazy to learn how to use them. I started to grind drills in 1954 so it is hard to break the habit.
Jimsehr
I even split the points on center drills.
 
Jim, you da' Man! I can barely see the tip of a center drill anymore, much less attempt to split the point. I used to hand grind all my drills too but as I got older I also got lazier and my eyes got blurrier so I went to a Drill Doctor. Now I can grind drills and split points but I'm still working on the lazy part.
 
Bob Korves said:
Here is a link on the subject. Do note it is on a CNC site, but that doesn't change much:
http://blog.cnccookbook.com/2017/02/27/when-to-use-a-spot-drill/
Click to expand...


Ok, so say all my drills are 118º . If I use a 60º center drill to spot drill a piece in the lathe chuck, the drill would start cutting some where else on the drills face, rather than the drill's point? So if I used a spot drill, it would need to be 120º, to make the drill bit actually start drilling at the drill bit's tip?
 
Mutt said:
Ok, so say all my drills are 118º . If I use a 60º center drill to spot drill a piece in the lathe chuck, the drill would start cutting some where else on the drills face, rather than the drill's point? So if I used a spot drill, it would need to be 120º, to make the drill bit actually start drilling at the drill bit's tip?
Click to expand...
Correct.
 
David S said:
This is really embarrassing having been doing this wrong all these years. Even the "pros" use regular centre drills.

David
Click to expand...
If you ask 10 machinists at random, most will say that the advice in this thread is all wrong. Try what we are saying here, and see how it works for you in your shop.
 
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