# Drilling brass & bronze



## PeterT (Feb 17, 2018)

Passing on some recent learning's. Drilling these materials can be exciting, especially larger diameters and/or deeper holes. Its amazingly easy to plant the drill in the metal, spin the drill, chuck or arbor - unsettling stuff. I experienced this when I made my C932/SAE 660 bronze bushings for the lathe & chocked it up to the material which I hadn't drilled before. Turning tools & boring bar worked great, but not big drills. Tweaking speed & feed didn't seem to help. The bits were new 118-deg HSS, very sharp. Under examination I noticed an ever so slight curve on the lip (some kind of funky grind) & maybe a bit higher rake angle. Bottom line is they are well made, cut steel effortlessly like a dream, but just asking for trouble in the 'B' materials. My old crappy drill set wasn't quite as bad on the same diameter, speed & feed but I had to baby it in deeper than 1".

So recently I took the HSS 0.375" drill & did a test hole in C932/SAE 660 bronze, 544 bronze and C360 free machining brass. That was also the order of 'grabbiness'. Then I dubbed the same drill like what is shown in Clickspring video. Nothing else changed. Same spot drill, same speed & feed. Difference was like night & day. It just walked into the material like it was a completely different alloy. I felt like a small miracle had occurred. So I dedicated some larger progressive drills to this dubbing treatment & I am going to get a set of reasonably priced HSS, dub them all & leave them reserved for this type of material. My personal conclusion is that dull drills might be masking this problem, but isn't really solving the issue which is the angle. 

Here's the procedure explained. I pre-blued my tips so I could see the modified edges with my magnifying glass, otherwise exact same treatment.


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## Bofobo (Feb 17, 2018)

Good tips


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## DPittman (Feb 17, 2018)

Well thats certainly good to know and I wonder how long it would have been ( if ever) it would've taken me to learn that tip.  Thanks for sharing.

Don


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