Gallery, Projects and General > How do I??
Drilling small holes
sbwhart:
Darren
The best brass for machining is called leaded brass it as a small % of lead in it that gives it better maching quality a lot of the bar brass you buy is leaded brass.
Now with sheet brass thats a different kettle of fish basically the more yellow the brass looks the higher the zinc content the more coppery it looks the more copper content I suppose thats obvious.
Some of the these grades of brass can be a bit gummy to machine especialy when you get around the 70/30 which is called cartridge brass this brass has got good deep drawing qualities but it doesn't turn so well.
Also sheet brass is sold in different hardnesess, basicaly what they do is work harden it as John said this could be happening, its quite easy to anneal it back just heat it up to cherry red hold it there for a few minutes and let it cool down or just quench it either way you'll end up with a softer material.
Hope this helps
Stew
Darren:
--- Quote from: Darren on May 03, 2009, 05:49:27 PM ---
Am I now to find it wasn't brass at all and some sort of alloy? It looks more yellow than other brass I have.....
--- End quote ---
I just realised wot I said there :doh: Brass is always some sort of alloy.... :ddb:
Anyhow, leaded brass, I have a bit of that and yes it's nice to machine. Not tried drilling it though.
Mine is round bar, does it come in other forms?
Stew, if I anneal this brass, should it last the course whilst I drill it before work hardening?
bogstandard:
Darren,
Now the full story is known, Stew has got it in one.
Good explanation Stew.
To allow him to shine even brighter, I will let Stew answer your question. He is the super expert on drawn brass.
John
sbwhart:
--- Quote from: Darren on May 03, 2009, 06:14:21 PM ---
--- Quote from: Darren on May 03, 2009, 05:49:27 PM ---
--- End quote ---
Anyhow, leaded brass, I have a bit of that and yes it's nice to machine. Not tried drilling it though.
Mine is round bar, does it come in other forms?
Stew, if I anneal this brass, should it last the course whilst I drill it before work hardening?
--- End quote ---
Leaded brass you can get it in most forms:- square, round, hex its a CZ spec I think its 133 but I can check
Annealing the brass depends what your going to do to it it will take a lot of machining to get it hard, but if your going to bash it and bend it it will soon harden up again.
Cheers
Stew
bogstandard:
Just a little extra onto what Stew has said.
Most of the copper based alloys will age harden all by themselves, so don't worry about the parts you have to soften, just by a bit of time and handling, they soon become strong enough to use in your normal situations.
I would now like to make clear about a statement I made in my earlier post
--- Quote ---is usually cured by stoning the cutting face to give zero rake.
--- End quote ---
Brass, when machined, likes to have no top rake on the cutter, and in the C-o-C I have shown the difference between lathe tool profiles to give you an idea of what I was on about. Don't get me wrong, most brass will cut with a top raked tool and give very acceptable results, but under certain conditions and types of brass, a zero rake tool will give superior finishes, so I keep one in my arsenal for those certain times.
It is the same when it comes to twist drills. You will have to excuse my rendition of a twist drill, I can never sketch helix correctly.
Sometimes, twist drills need the same sort of treatment, and is is very easy to do. Holding the drill vertical, rub up and down a few strokes with a stone or diamond lap against the cutting edge, again in a vertical motion. No need to go overboard, just a couple of swipes is enough. This gives the drill version of zero top rake, and you should find that brass cuts a lot easier with no snatching.
I used to have complete drill sets treated in such a way, but after a time I used to get them mixed up with my other drills, and so started having problems drilling into normal materials. So now I use normal ones, and if needed, modify a spare to get the job done.
Bogs
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