Drilling Brass: the easy and safe way

I remember my dad showing me this drilling brass trick more than 30 years ago. And who better to show you, other than the guys on the Home Model Engine Machinist forum because they really know their stuff when it comes to tricky machining jobs. Here is what Deanofid had to say about an easy way to modify a standard metal HSS drill bit to easily (and safely) drill holes in brass…

Brass has a tendency to grab the sharp edge on drill bits. Bits for brass, whether drill bits or turning bits for the lathe are supposed to have a zero rake cutting edge. That way, they will not grab, and, it’s simply the proper tool bit geometry for brass.

I keep an extra set of drill bits just for brass. All ground as shown below.

This is how a stock drill bit looks on the end. It comes to a very sharp edge where the bit cuts metal (arrow). That same sharp edge that cuts steel so well will also dig in hard in brass and suck the bit into the work.

To take that sharp edge down, you run the cutting edge of the bit along a honing stone. The idea is to make it flat, which is no good for cutting steel, but cuts brass very well, and stops the grabbing problem. Run the bit in the direction of the arrow towards you, honing in only one direction. It usually takes 3–5 strokes to get the sharp edge off and condition it for brass cutting. (I realize the arrow has two heads, but hone the bit in only one direction.)

When you are done it will look like this. The shiny part you see is where the sharp edge has been honed down flat. It only takes a very small flat to be effective. No more grabbing.

Thanks Deanofid! I hope that this is useful for you, I know I got into trouble the first time I tried to drill brass before my fathers old advice made a ‘too late’ return into my head. And me the son of a fitter and turner, oh the shame of it…

Stay well

Ian

Originally published at handycrowd.com.