Drilling Brass for beginners.

Please ignore this post if you already know how to drill brass safely!

Hi All
One material I am not keen on machining is brass. It is not a difficult material to work with but there are some issues when machining. Also the brass swarf gets everywhere and makes cleaning down the machines a nightmare.
Anyway getting back to drilling brass.
When drilling brass there are several things to be aware of when using a standard 118 degree twist drill. Cutting speed 90-210 m/min, Coolant, drilling to required diameter in one pass (not stepping drill sizes) But most important is drill point preparation.
A standard drill tends to snatch at the brass and drag itself into the workpiece.
To prevent this the cutting edge can easily be modified with either a oil stone or my preferred way is a offhand grinder.

The photos below show the drill point for brass.


Attachment 43989
Both drills are 20mm diameter. The lower drill is a standard drill and the one above has been modified for brass.

Attachment 43990
Right drill has negative rake for brass.

Attachment 43992
Centre drilled and drilled at 20mm so the drill has less chance of snatching. If the hole was to be 30mm diameter a 30mm drill would have been used after centre drilling.

Attachment 43994
Drill chips are removed like small needles.

Attachment 43995
Brass swarf collected on a rag to aid clean up.

I hope this will be helpful to those that are not use to machining or thinking of using brass in there future projects.
The Home Engineer

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I'd like to see some closeups of the modified bit.

Ralph

Thanks, Andy. Coincidentally, I was drilling brass yesterday, something I do not often do. I found 2 or 3 jobbers that had already been flatted. But I don’t know where they are now! But I thought that brass did not coolant?

Hi Philip
The coolant not only helps cool the drill and job it also helps direct the swarf so it doesn’t go all over the place. I haven’t made anything in brass for ages and like buses I have decided to make the siren for the foden which is phosphorus bronze and brass.

Hi Ralph
please find photos of modified drill bit for brass.

Attachment 44070Attachment 44071Attachment 44072

This is how I grind them against the side of the wheel. Very light grind in one pass on both cutting edges

Attachment 44074

Hope this helps
The Home Engineer

The first time I drilled brass I was in for a BIG surprise. Brass shot out like a machine gun. Then I read to try a slightly dull drill. I ran a sharpening stone across the cutting edge 2 strokes and no more problems. Works great.

It's not exactly dulling the drill, but removing very edge of the rake, the helix that extracts chips, essentially parallel to the drill axis. It keeps the bit from 'accelerating' into those type materials. Brass and bronze top that list, certain grades of copper.
It's a lot like the reaction hand drilling sheet metal with a twist bit, as it advances faster than cutting, more or less screwing into the material. The newer remedy is the Unibit, step drill, 'peeler bit' that moves material instead from the side.

An effective method is a whetstone, drawn away from the cutting edge, not as a file going in, which can round off the cutting edge. As mdhatter3 mentions, a couple strokes is all it takes.