Odd drill bit

cdhknives

cdhknives

Active User
H-M Supporter Gold Member
While going through the drawers of my Grandfather's old lathe I found a strange drill bit. It is a 2 flute twist drill at first glance, but while looking at the tip to check the sharpness it looked really strange. First, the tip is flat. For a bit that mic's at 0.6975" the flat tip is around 1/8" in diameter...and it looks ground, not hammered or burned off. Second one flute is MUCH bigger than the other, both in depth and width.

The picture is a little dark, but the flutes are obvious.

What is this for?

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from the picture it looks like it may have a carbide tip --maybe take a picture from the tip end--your picture isn't very clear to me
 
Its really hard to tell from the photo... I am half tempted to say it was ground for brass, with the cutting edge ground perpendicular to the work piece, but I'm not completely clear on what you are describing, and the photo is not a ton of help..

Can you take a clearer photo, of exactly what you are talking about?

-Cody
 
I don't know better how to describe it. One flute is double (or more) the width and depth of the other. The very tip of the bit (most of the web portion of the tip) is flat/blunt. There is obvious discoloration from overheating which makes the tip hard to photograph, but it is NOT carbide. It is NOT an optical illusion in the photo. The cutting edges on the tip are wildly different lengths from the flute difference. The toolmarks in the flutes look like a normal factory grind too, not the result of some fancy Dremel work. The flute depths are uniform from tip to shank. This lathe has sat for over 20 years since my grandfather died, so the bit is older than that.

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20130717_223247_zps6f69c9a2.jpg 20130717_223307_zps380391b1.jpg 20130717_223223_zps14c27201.jpg
 
Your grandfather may have ground it himself to champher a flat botom shallow hole in brass and the flat tip would keep bit from pulling deeper.--a lot of old timers made special grinds for a special need--if you say the end was discolored like it got hot, then I'm not sure---maybe someone else will know why it is like it is. Dave.--**one thing is, you can just regrind it to a normal bit again
:thinking:
 
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I know what its for!!! Weighting the trash can so it doesn't blow away!!!

But seriously, it looks to me like a re-grind that was never completed, or even started.

-Cody
 
The guy above is right. The "hook" has been taken out, normally for a brass application to reduce the burr generated when the hole breaks through. I grind them for the guys at work at least once a week. They will come up and ask me to take the hook out.
 
The way to grind a drill so it doesn't pull through brass is to grind the cutting edges vertical,so the drill only scrapes its way through. The only reason I can see for the flat nose is he could be using it for a core drill,a type of reamer. But,real,purpose made core drills have several flutes. So,if it was used as a core drill,it's a crude attempt. But,old timers most often got along with what they had on hand.
 
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