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Hardening brass

Doggggboy

Doggggboy

Ultra Member
I am trying to use a small piece of brass 30.06 casing to fix an indexing post on an air rifle.
Initially I cut a piece to fit but then it snapped when I was trying to bend it into the correct shape.
A quick readup on annealing and now the replacement piece is soft and perfectly formable.
The problem is I can't get it to harden again. It forms a spring piece shaped like a V with the left side looking more like a 7 and it has to be stiff and springy.
I've tried heating and quenching but that doesn't seem to be working very well and the piece is still too soft to be useful.
The original part may have been copper but I don't have any thin copper plate laying around and thought brass would be close enough. It is the flat bent part in the image. 1/32 thick and 7/32 wide.

Edit..... Tried heating and quenching again but just barely making it hot instead of red hot before quenching.
Seems to be much more springy now. It will work until it doesn't I guess.
There is a newer version that uses a solid pawl instead of the spring but at around £60 to get it here I'll dick around with this first.
1744937024125.png
 
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Brass will work harden. Heating anneals it, whether you quench or not. I.e. after firing a shell, which expands to the chamber, and then resizing it, will hardened the brass case. The more often it's repeated, the harder it gets to the point were you get neck splits. By annealing the neck/shoulder area, you will extend the life of the case, and get more consistent neck tension shot-to-shot.
 
thestelster said:
Brass will work harden. Heating anneals it, whether you quench or not. I.e. after firing a shell, which expands to the chamber, and then resizing it, will hardened the brass case. The more often it's repeated, the harder it gets to the point were you get neck splits. By annealing the neck/shoulder area, you will extend the life of the case, and get more consistent neck tension shot-to-shot.
Click to expand...
So how much work does it actually take to work harden? Like, if I flex this tiny piece back and forth am I looking at 10 repetitions or 1000 repetitions before it hardens? I can't just hammer on it to harden it and then try forming again or it will just break again won't it?
 
Tom O said:
I was thinking about the spring type piece over the rotating wheel.View attachment 63367
Click to expand...
That might be an option. I've got several bits of flat spring steel kicking around somewhere.
I've asked the manufacturer if they could send me some drawings of the replacement upgrade that uses a pawl instead of the spring.
We'll see. The upgrade looks like this and if wasn't going to cost 80 bucks for something I could hide under a loonie I'd have one ordered already.
1744948591988.png
 
Doggggboy said:
So how much work does it actually take to work harden? Like, if I flex this tiny piece back and forth am I looking at 10 repetitions or 1000 repetitions before it hardens? I can't just hammer on it to harden it and then try forming again or it will just break again won't it?
Click to expand...
I have no clue. Sorry.
 
Doggggboy said:
So how much work does it actually take to work harden? Like, if I flex this tiny piece back and forth am I looking at 10 repetitions or 1000 repetitions before it hardens? I can't just hammer on it to harden it and then try forming again or it will just break again won't it?
Click to expand...

There is no simple solution or specific answer to your question. The best answer is "it depends" there are simply too many variables in the process.

When brass work hardens, it isn't a singular event. Instead it is a series of smaller steps where individual grains of metal form new boundaries that resist dislocation. So work hardening progresses with impact or bending or stretching from a few grains to many in a sort of progression from all soft, to a few hard, to many hard. How much you beat it, or bend it, or stretch it matters. Eventually, this work hardening reaches a point where failures (cracks) start to occur.

Anealling heats the grains and allows their boundaries to grow and rejoin forming larger softer grains. Basically, annealing heals the grain structure returning the metal to its original condition. But even so, the process is not linear or defined. It takes place over time, from many fractured harder grains converting back to larger softer grains in a slow progression. How hot, how long, how uniform - all matter.

It depends.
 
Doggggboy said:
That might be an option. I've got several bits of flat spring steel kicking around somewhere.
I've asked the manufacturer if they could send me some drawings of the replacement upgrade that uses a pawl instead of the spring.
We'll see. The upgrade looks like this and if wasn't going to cost 80 bucks for something I could hide under a loonie I'd have one ordered already.
View attachment 63368
Click to expand...
You have a picture, that makes you more than half-way to done! Make the part yourself.

As mentioned, all you get from repeatedly heating Brass, is dead soft brass, as you discovered. Quenching Brass after heating it serves to minimize the formation of oxides, and makes it that much faster than you can handle it with bare fingers, but has no net effect as far as the hardness goes, the heat treat magic is ALL in the raising of the temperature!

FWIW, drawing a line on hard brass sheet or higher temper aluminum, with a Sharpie Marker, and waving a torch over the part until the line vanishes from the heat, is a pretty low-rent but effective means of judging how much heat to apply. Handy for when you have need of doing a tight radius bend on a brake that you don't have packings for (nested layers of material, to create a larger radius at the Brake's nose) or when the sheet just doesn't want to bend without snapping along the bend line.

Work hardening, as mentioned, is the only method to harden Brass. your options are usually to start with sheet or a cast blank, that is twice as thick as you want the final part, and either hammer it to half thickness, or run it through a roller mill about the same.

Another option is to source some Beryllium-Copper spring material as sheet stock, cut out your profile, and cold form the shape you need around a set of pins or using a bending jig. Be-Cu is pretty safe to work with, using basic precautions, which boil down to the following. Don't make smoke or sparks. Don't make dust. Wash your hands before eating or smoking. So no welding the stuff, no buffing or grinder work, and keep your work area nad hands away from body orifices, until after washing thoroughly.
 
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