Drilling brass - not as easy as you'd think !

[mikepilk]

I knocked up this left handed winder this afternoon - I got fed up with Seiko springs pinging out of washers as I tried to reverse them !

I bought the brass from a model shop, and as it's easy to cut and file, I assumed drilling it would be easy. Not 

I broke 2 drills and got nowhere, before finding that lots of oil and a very low speed seemed to (slowly) work.
(I don't have a lathe, or mounted drill,  so all was done free-hand with a cordless drill. My dremel type drill seemed much too fast to cut).

So my question is, what is the best way to drill brass ?

The handle is currently screwed to the arbor - but as it's winding left hand, it tends to undo. So I plan to either use epoxy, or solder the bits together.

Edited February 5, 2021 by mikepilk

[nickelsilver]

Brass wants zero rake angle. If you are turning it on a lathe that means that your tool will have flat top (or close to it) rather than say a 15ish degree angle for steel. With a drill, the rake is built into the twist. So, you do what's called "dubbing", which is to put a flat on the cutting edge that's in line with the body of the drill. You are making a zero rake cutting edge, and even if very small, makes a big difference in brass.

 

If you don't do it, it wants to sort of screw itself into the work, grabbing and sometimes breaking, or with sheet brass grabbing and spinning it around to smash and slice your fingers.

 

Just did a quick check to cheat and find some pics illustrating it and there's a vid by Clickspring! I haven't watched it but all his videos are fantastic so here it is.

 

 

[mikepilk]

7 minutes ago, nickelsilver said:

Brass wants zero rake angle. If you are turning it on a lathe that means that your tool will have flat top (or close to it) rather than say a 15ish degree angle for steel. With a drill, the rake is built into the twist. So, you do what's called "dubbing", which is to put a flat on the cutting edge that's in line with the body of the drill. You are making a zero rake cutting edge, and even if very small, makes a big difference in brass.

 

That may explain why broken drills worked better than new ones !

The problem was the drills just weren't cutting. I bought new "jewellery drills" from Cousins, which are claimed to be suitable for brass.

Edited February 5, 2021 by mikepilk

[nickelsilver]

Hmm, never heard of a jewelry drill. Some brass is just crappy* and gummy, but my experience with model shop brass is it's pretty good (as you found sawing and filing). I suspect you might have not-so good drills. Brass is usually machined dry too, but for drilling it can help to use a little oil. A real cutting oil is best, but any will do.

 

*I have some brass shim stock that I use for wheel blanks and such. Cutting dry it makes horrible burrs and breaks endmills. Bit of oil and all's good.

[mikepilk]

The "jewellery drills" all have the same shank size (2.35 mm). 

I haven't been able to find any good quality drills at a reasonable price - as all my drilling is hand held, I will break bits.

Cousins sell Dormer, the < 1mm are about £3 each.  The only other option are the ultra cheap Chinese ones, which seem to be have the strength and cutting ability of cheese.

[nickelsilver]

Ah ok, they're intended for use in motorized handpieces.

 

Reasonable price and high quality is a hard combination. The small (sub 1mm) drills I use are 4-5 bucks apiece, sold in boxes of 10 haha. About 18 years ago I bought a set of drills 1mm to 10mm by 0.1mm steps. New price was something like 600 but I found this secondhand complete and the few drills that had been used were professionally reground for a couple hundred. I have only replaced 3 or 4 in all those years, and while I'm not doing large work all the time they get used by several other people who share my workshop. So pretty cheap end of the day!

[oldhippy]

I don't know what drills you are using but when I was working my drills went through brass like a knife through butter. Are they all blunt? brass is soft compared to other metals. 

[wls1971]

The Dremmel should cut through brass, before I got a sensitive drill I used to cut through brass with one I always started the hole off first with a center punch to stop the drill bit skidding on the brass surface. I always clamped the brass to a piece of wood to keep it steady.

[mikepilk]

56 minutes ago, oldhippy said:

I don't know what drills you are using but when I was working my drills went through brass like a knife through butter. Are they all blunt? brass is soft compared to other metals. 

They are brand new ones from Cousins, which are sold as suitable for drilling brass. I was expecting them to easily drill.

So there isn't a problem, apart from the 'grabbing' highlighted by @nickelsilver, I just bought crap drills !

Edited February 5, 2021 by mikepilk

[jdm]

2 hours ago, nickelsilver said:

About 18 years ago I bought a set of drills 1mm to 10mm by 0.1mm steps. New price was something like 600 .

I bought one of these recently for a fraction of that. Reputable seller, Co5 / coating and most probably made in China. The index are metal and having them on the shelf builds confidence and sends away the need to ever use them. If and when they will need regrind I'll just watch some Stefan Gotteswinter videos, and then get busy with my new €3.50 tool 

 

[nickelsilver]

Just a little thing but are you turning the right way? When I was in school there was a classmate a making a winding stem with the lathe in reverse. He was stessing because he wasn't getting  curly chips, just dust. Just before he finished the instructor saw the problem.  Stem was fine, and we gave him sh!t for it till the end.

[mikepilk]

Yes, they were so useless I did check they were turning the right way! 

I'll buy some better quality drills and one of those sharpeners. 

[Watcher]

Try this supplier

https://drillbitsunlimited.com/

[JohnR725]

18 hours ago, mikepilk said:

brass from a model shop

 

18 hours ago, nickelsilver said:

Some brass is just crappy* and gummy, but my experience with model shop brass is it's pretty good (as you found sawing and filing).

One of the problems with the term brass is that they can refer to a whole bunch of different alloys. Then what about bronze could it be mistaken for brass? The hobby store stuff should be fine. It's only really when you start buying generic material could you conceivably end up with awed problems because it's not really easy to work brass.

Just like I've heard of several stories of people making stuff one person was making a flat spring for a watch another person was making a cutter for a gear. Both of them discovered that their shiny steel didn't harden at all. Because they had zero idea what they were actually working with.

[Klassiker]

On 2/5/2021 at 6:14 PM, nickelsilver said:

Just did a quick check to cheat and find some pics illustrating it and there's a vid by Clickspring! I haven't watched it but all his videos are fantastic so here it is.

By the way, I checked out this video, and it is very good, as are all the others I watched. In fact, they are so good I can't stop watching them. This week was a Clickspring and repivot22 binge! I haven't got around to anything  else, so, er, thanks for the recommendation!

[jdm]

45 minutes ago, Klassiker said:

By the way, I checked out this video, and it is very good, as are all the others I watched. In fact, they are so good I can't stop watching them. This week was a Clickspring and repivot22 binge!

Second that, YT is too addictive, best is to limit oneself to 20mins before sleeping.

Clickspring is a bit too much "produced" for my own personal taste, about miniature work I started watching Joe Pieczynski, for direct and very practical learning.

[rodabod]

Mike, any good quality HSS drill bits should be fine with brass. Even some of the Chinese ones are useable. There are lots of aspects to technique which may help. Graduating in size from a very small pilot drill but may help. 
 

The brass you are using looks like typical free-machining brass which is designed to be easy to work with as it has a higher lead content which helps it to chip/crumble. The more difficult stuff is engraving brass - the sort we like for antique clock work which is less “machinable” but produces amazing ribbons when you turn it on the lathe. 

[mikepilk]

59 minutes ago, rodabod said:

Mike, any good quality HSS drill bits should be fine with brass. Even some of the Chinese ones are useable. There are lots of aspects to technique which may help. Graduating in size from a very small pilot drill but may help. 
 

The brass you are using looks like typical free-machining brass which is designed to be easy to work with as it has a higher lead content which helps it to chip/crumble. The more difficult stuff is engraving brass - the sort we like for antique clock work which is less “machinable” but produces amazing ribbons when you turn it on the lathe. 

I was expecting it to be easy, especially as I had bought some new "German" drills from Cousins to replace my cheap Chinese ones. That's why I was surprised when I had so much difficulty. It turns out that the drills are rubbish.  I sharpened some of my old broken Chinese drill bits using a diamond file, and they cut fine. 

[rodabod]

That’s really interesting. It could be a rake issue, as Nick mentions, but possibly not. 

[mikepilk]

12 hours ago, rodabod said:

That’s really interesting. It could be a rake issue, as Nick mentions, but possibly not. 

I'll have to do some research on drill angles - something I know nothing about. But looking under the microscope - the ends are just ground off flat - no 'relief' (?) angle (see pics below). 

I just had a go re-sharpening using a dremel and fine stone - but that's much too aggressive on small drills.

I have a 1000# diamond knife sharpening 'stone' - holding the drills in a pin vice and working under the microscope, seems to work nicely. But I haven't figured out the technique yet : not sure how to get the relief angle. 

But even after my first attempt, the drills cut much better.

Edited February 15, 2021 by mikepilk

[rodabod]

It’s quite easy to sharpen them “under hand” like your describe with a sharpening stone. Even chipped carbide bits!

[mikepilk]

34 minutes ago, rodabod said:

It’s quite easy to sharpen them “under hand” like your describe with a sharpening stone. Even chipped carbide bits!

Just getting rid of the flat faces has made a big difference - they actually cut now !

The flat faces weren't allowing the drill to bite in to the surface - just heating the drill and polishing+hardening the brass.

At least I know I can use the drills and not bin them.

[rodabod]

Should be able to make your own “spade” bits and D-bits no bother now too. Just need some silver-steel rod, a file, and lamp or torch to heat treat them. 

[nickelsilver]

34 minutes ago, rodabod said:

Should be able to make your own “spade” bits and D-bits no bother now too. Just need some silver-steel rod, a file, and lamp or torch to heat treat them. 

I make spade bits all the time for repivotiong work. From carbide, the beauty is you can "waist" it, so in the event of breakage it just falls out. Smallest I've done is 0.10 (that's a nerve wracker!).

 

D-bits are fantastic for very precise straight holes.

[mikepilk]

3 hours ago, nickelsilver said:

I make spade bits all the time for repivotiong work. From carbide, the beauty is you can "waist" it, so in the event of breakage it just falls out. Smallest I've done is 0.10 (that's a nerve wracker!).

 

D-bits are fantastic for very precise straight holes.

I guess a "spade" bit is what is called in my Fried book a "pivot drill" ?

Can I use what Cousins calls "pivot steel" to make them ?

I don't have a lathe, but I could put some in a drill and use a file to create the waist.

What is a D-bit ?