Is bronze grabby?

[NCjeeper]

Just curious. 9/16 import gave up.

 

[jbobb1]

Looks like a drill bit failure to me. Some grades of bronze can be a pickle to machine, but that don't look to be your issue.

 

[great white]

Yeep. I've never had a drill bit fail like that. I'd guesstimate a manufacturing defect in the bit itself.

Is there any evidence of a rusty or dirty spot at the beginning or end of the break? it could indicate a crack that wasn't picked up when they hardened the flutes. How about the grain in the break? Does it look like smooth steel or does it have a "gravelly" look to it?

 

[mattthemuppet2]

yikes! Bronze and brass are grabby in my experience, and brass will certainly autofeed. Also looks like you had a lot of chatter - did you drill a pilot hole? Sometimes you get better holes just by plowing straight through in one go.

 

[NCjeeper]

yikes! Bronze and brass are grabby in my experience, and brass will certainly autofeed.

Yeah that was a little tongue in cheek there.

 

[682bear]

Wow! It should take a lot more than that to break a 9/16...

-Bear

 

[ChazzC]

Yes, brass & bronze can grab, help see my previous post (and others) in this thread. Hovever, the hole doesn’t show signs of grabbing, just chatter (as noted by @mattthemuppet2). I suspect a bad bit.

 

[C-Bag]

I read on a site dedicated to tool sharpening that most drills that are set up for steel at 7deg and he suggested 4-5deg for brass and bronze. Works good for me and also slower rpm.

 

[benmychree]

For brass (especially) and bronze (sometimes it is the best policy to put a "brass edge" on the cutting face of the drill, that is, a small flat to negate the spiral rake angle, this will eliminate the grabbing/ self feeding.

 

[682bear]

I had an import bit grab a few years ago...



...straightened it right out!

-Bear