# Drilling Brass



## ollie (May 27, 2008)

Hello: I am having difficulty drilling a quality hole in brass. My drills are sharp and tend to grab. I have read references to using bits especially ground for brass, but I cannot find instructions on the process using the search engine. Could anyone direct me to a previous post on the subject, or explain how to grind a bit for drilling brass? Any help would be appreciated.  Thanks, Ollie.


----------



## SandyC (May 27, 2008)

Hi Ollie,

A standard drill, correctly sharpened for steel has a positive rake on the cutting edges.
This will snatch with Brass or Bronze.

To adjust for brass, take a small oil stone and take the sharp cutting edges off, in line with the azis of the drill.

this will result in a zero rake cutting edge, suitable for brass. (see attached PDF file)
You only need a small flat.

Of course, the drill will no longer be suitable for steel so, if you can, use a second set of drills specialy sharpened for brass.
Otherwise, you will need to re-sharpen for steel.

Hope this helps.

SandyC ;D  

View attachment Brass drill geometry.pdf


----------



## Mcgyver (May 27, 2008)

like Sandy says, you have to have zero rake on a drill (or lathe work) for brass - some beginners have trouble understanding where the rake angle is on a drill. if you stop motioned a drill cutting and cross sectioned it, it would look a lot like a lathe tool bit ploughing through a cut which should make it clear where the rake and clearance angles are. From the cutting edge, the rake is formed by the flute whereas the heel creates a clearance angle - its the heel that you grind when sharpening the drill. With a drill vertical to the work, and the cutting edge contacting the work, the angle of the the flute surface, is where the rake angle is formed. If you look at how this edge moves through the material, because of the helix angle of the flute, the angle of the cutting edge is less than vertical, creating positive rake - exactly the same way a lathe tool has positive rake on top; the surface that produce the shear. clear as mud? the pics will help.







we're taking the angle formed where the flute meets the cutting edge, and making it a vertical - and by doing so, its 90 degrees to the work or zero rake!

here is how its created, oriented the drill as show and just give it a light touch to the grinding wheel. unlike sharpening, you;re grinding on the flute not the heel 






for smaller drills, just use a stone. The stone is only sitting in the vice so it could remain stationary while i took 100 pics with the POS P&S hoping for one in focus. maybe time to update this shot - i now have an slr (yippy)






hope that helps some. you are better off acquiring addition sets for brass - otherwise its a pita as you'll have to take a far bit off the end to us them again on ferrous, AL, etc.


----------



## ollie (May 27, 2008)

SandyC and Mcgyver: Thanks for the excellent explanation of the sharpening process. Now I just have to keep the "Brass" bits in a separate box than the "Steel" bits. 

Thanks again, Ollie.


----------



## tmuir (May 28, 2008)

Thanks for that.
It's been a good day as I've just learnt something new, but this does mean now I need a set of brass and a set of steel drills. Just when you think you have bought everything you need, you realise your not even close. :


----------



## DICKEYBIRD (May 28, 2008)

Hey Mcgyver, et al:

Thanks for the tutorial...you wouldn't believe what my mental image of a zero-rake cutting edge was until now. 

Since brass is _relatively_ soft, does this mean a feller could, in good conscience, buy a cheap-o set of drills from H/F or the like and modify them for brass? Save the good ones for harder metals?

I've got one of those Grizzly (Chinese) 118 piece sets I got as a "free" gift when I bought my mill from them and am thinking they would do fine if ground & dedicated to do brass work. That's assuming I ever become wealthy enough to own some brass of course. ;D


----------



## Bogstandard (May 28, 2008)

Drill sets are so cheap now, you can have a set just for brass.

In fact I change all my drills every year, saves having to worry about sharpening them.
The ones from last year just go into a rough drills box, to be used for things like brass or tuffstuff that is liable to knock the cutting edges off, or are raided to replace ones that I manage to break this year.

John


----------



## CrewCab (May 28, 2008)

tmuir  said:
			
		

> Thanks for that.
> It's been a good day as I've just learnt something new



Me too ;D ............ again ........... as for having everything you need I doubt that will ever happen here as I'm only just starting ............. the good news is I have plenty of old drills though, at least I can practice on those.

Dave


----------



## mklotz (May 28, 2008)

You'll quickly find that those brass drills are just the ticket for drilling a lot of plastics too. No more snags when you break through.


----------



## tel (May 28, 2008)

ollie  said:
			
		

> SandyC and Mcgyver: Thanks for the excellent explanation of the sharpening process. Now I just have to keep the "Brass" bits in a separate box than the "Steel" bits.
> 
> Thanks again, Ollie.



I might be stating the bleedin' obvious here, but make two drill stands, one of brass and one of steel.


----------



## CrewCab (May 28, 2008)

tel  said:
			
		

> I might be stating the bleedin' obvious here, but make two drill stands



Obvious ......... probably ........ but a good point Tel ;D

In my case methinks 4 
1 x Steel
1 x Brass
2 x For the rest of the dam things I can't bear to throw away (probaby need more than 2  )

As always Tel ......... good to hear from you, how's life "upside down" treating you  ............ btw ...... you were spot on about the belt drive kit for the Mini Mill, much better machine now 

atb

Dave


----------



## shred (May 28, 2008)

tel  said:
			
		

> I might be stating the bleedin' obvious here, but make two drill stands, one of brass and one of steel.


A spray of layout fluid, ink or paint down the flutes is also a good way to color-code 'special' drills and sets. Just re-paint every so often as it wears off.


----------



## tel (May 29, 2008)

Your drill collection sounds like mine Dave - I got hundreds and hundreds of the things - can't bear to throw even the broken ones out.

Life's OK down 'ere mate, except it's totally forgot how to rain in our neck o' the woods.


----------



## CrewCab (May 29, 2008)

tel  said:
			
		

> Life's OK down 'ere mate, except it's totally forgot how to rain in our neck o' the woods.



Rain we have a plenty Tel ??? ................ just wish I could figure out how to swap it for some of your sunshine ;D

Dave


----------

