How are drill bits made?

[Bill S]

I found this in a pack of #1 drill bits and it begs the question, how are drill bits made? It looks as if it got fouled up in the manufacturing process. Are the slots cut straight and then twisted, as in twist drill. Or are they cut with the twist?

 

[rake60]

Interesting Picture.

Originally twist bits were made by cutting grooves in opposite
sides of round stock that was then twisted to form the flutes.
That process was patented in 1863.

The flutes in modern drill bits are ground into the blank with
the stock rotating through the tool grinder.

I'd have no idea how that example came to be.

 

[Lew Hartswick]

I've heard that some Harbor Freight drills look like that after one use. It obviously wasen't hardened.
...lew...

 

[Loose nut]

Maybe the grinder operator changed his mind half way through the job.

 

[Stan]

I bought an import masonary bit that unwound into a flat bar the first time I used it.

 

[greenie]

I found this in a pack of #1 drill bits and it begs the question, how are drill bits made? It looks as if it got fouled up in the manufacturing process. Are the slots cut straight and then twisted, as in twist drill. Or are they cut with the twist?

Nope, not fouled up due to the manufacturing process, that bit has been used and it has grabbed on the break out and then the flutes have unwound. Reason being, that the drill was not hardened correctly, or they have used inferior materials to make the drill bit. Better just chuck the rest of the packet in the bin and don't buy any more of that brand.
The easiest way to explain how most twist drills are made is that they start life as a large coil of black wire of the correct grade, this is sent through machines to straighten it out and then the blanks are cut to length.
Two ways of going about making them at this point, first way is to put the blanks through another machine that holds them at the end and then they are induction heated and then the flute is rolled in whilst it is hot, or they go into a machine that grinds the flutes into the blank.
Then into the centreless grinder to size them to what ever they need to be, then over to another machine to grind the relief into them, followed by the drill point being ground onto it.
Actually quite a few of these processes are very finely tuned, to make a twist drill the correct size, there is a lot more to it, than this simple explanation.
Had a 24mm drill of chinese origin do the same thing, you could have used it for a left hand drill after it unwound.
regards greenie

 

[Bernd]

Unless that picture is a mirror image it looks like that was once a left hand drill. Am I seeing that right?

Bernd

 

[Circlip]

Photo looks to be mirrored cos it looks to read H.S.S. on the end of the shank, BUT I bet it isn't :big: Ian.

 

[AlanHaisley]

Unless that picture is a mirror image it looks like that was once a left hand drill. Am I seeing that right?

Bernd

No, it looks right handed if you look at where the flutes start on the right and where the grind is there. It looks like someone was fooling around and heated the middle with a torch then gave the thing a twist with some pliers.

Alan

 

[Bill S]

No, the shot isn't mirrored. The bit is righthanded at the shank, but at the tip it is left. I hadn't noticed that before. I'll post a pic of the tip later.

 

[Bill S]

Here's another shot of the bit. It appears that it started life as a right-hand drill as you can make out the relief cut on the flute is for right-hand. The tip seems to be perfectly formed as a left-hand. Even though the tip appears to have been used, I think it was purposely made by someone at the factory foolin' around.

 

[gilessim]

I think you may be right there Bill!, a right hand twist doesn't turn into a left hand twist, I found the photo a bit of a headspinner!

I bought a pack of 10 1/8" bits a while ago, of good quality ( UK made ,forged not ground) and one was flat all the way down one side, I didn't notice and wondered why it wouldn't run true until I looked more closely!

Funny old world isn't it?

Giles