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Bending brass - hot, warm or cold?

-that's the question

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Versaboss06/04/2021 22:23:02
470 forum posts
51 photos

Hello all,

I'm trying to produce two small cocks (for relieving cylinder pressure at the ends of a steam cylinder, I'm not sure what the correct name for these is). Anyway I tried to bend the actuating stem (brass, 3 mm dia.) about 30°. I warmed the place where the bend had to be with a small gas burner, but the brass broke already after a very small bend.
I'm wondering now if there is a better method - either VERY hot or cold?
I'm trying to save the part by building it from two parts, soldered together. it would be difficult to reproduce the part, as I lost the angle for turning the taper.

Any help appreciated,
Hans

bernard towers06/04/2021 22:29:29
277 forum posts
84 photos

Anneal it first

John Haine06/04/2021 22:30:39
4116 forum posts
241 photos

I think somewhere I read that you need to get brass VERY hot to anneal it before bending, I'll try to find the reference.

Michael Gilligan06/04/2021 22:38:52
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18761 forum posts
922 photos

A potentially tricky, and unpredictable, job sad

A lot depends on the grade of Brass [which may not be known]

Brass is not so much a true alloy, but a mixture
... and if you heat it too much, it can de-zincify

there may also be significant lead content to complicate things.

MichaelG.

Michael Gilligan06/04/2021 23:51:20
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18761 forum posts
922 photos

This may help : **LINK**

https://www.copper.org/resources/properties/microstructure/brasses.html

MichaelG.

larry phelan 107/04/2021 09:55:02
1079 forum posts
14 photos

One of my jobs in a past life was to bend 1/4" round brass bar to 90deg. I heated it to red heat, let it cool then bent it.

SillyOldDuffer07/04/2021 11:30:30
Moderator
7487 forum posts
1658 photos

As Michael says, much depends on the Brass. One of my old books says the properties of Brass alloys vary so much between extremes that they should be considered entirely different metals.

Brass formulated for casting (plumbing), doesn't anneal or bend well. Naval Brass is strong, not very malleable, and formulated for corrosion resistance. Brass with Lead in it doesn't anneal.

Cartridge Brass is specifically formulated to facilitate cold drawing and forming, which is ideal, but even it work hardens rapidly making it necessary to re-anneal at each of about nine stages from blank metal to finished cartridge. Plenty of advice on the web about annealing cartridges.

The important thing is not to overheat the Brass, but that temperature depends on the alloy, between 300 and 700°. Common brass anneal at about 450°, a little under dull red-heat in the dark (approx 500°C).

Don't know what alloy Jewellery brass is, except its soft and quenched in alcohol. Other brasses are left to air cool. Unfortunately the book I have to hand is vague about Brass, I'll look for another.

Dave

JasonB07/04/2021 11:38:10
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Moderator
21327 forum posts
2424 photos
1 articles

When I have made drain cocks I used 303 stainless for the tapered part and easily bent the handle. Although the softer brasses bend well it's not easy to find small lengths in round section.

Clive Brown 107/04/2021 14:33:44
690 forum posts
33 photos

I've recently made a couple of drain-cock handles from drawn phosphor bronze rod, 3/16" dia. They bent through about 80 deg. with no sign of cracking, no annealing required. the dia. at the bend is .090" ish.p1020887.jpg

Edited By Clive Brown 1 on 07/04/2021 14:35:52

Gareth Jones 907/04/2021 21:18:55
21 forum posts

I've recently been annealing brass by using a 50/50 salt bath of Potassium Nitrate/Sodium Nitrite. Temp is controlled by use of a digital thermometer fitted with thermocouple. The salt is contained in a steel welded crucible and heated with a propane torch. Target annealing temp is something like 350 to 400 deg C.

I saw the set up described in Tubal Cain's Hardening, Tempering and Heat Treatment in the Workshop Practise series of books.

Gareth

Versaboss07/04/2021 21:50:16
470 forum posts
51 photos

Well, that's a lot of stuff to digest! In the meantime I decided to go the easy route and am making new cocks from some stuff I have which is called (by the supplier, Bergeon) "Nickel". I believe it is not really pure nickel, but rather German Silver. I could bend a sample easily without breaking. But as I expected, getting the same angle again on the conical part was almost impossible. I think applying a dab of Timesaver will be necessary.

If the drain cocks (now I know the word, thanks) come out only half as good as these from Clive Brown, I will be happy!

Many thanks to all for your help,
Hans

Edited By Versaboss on 07/04/2021 21:50:54

Edited By Versaboss on 07/04/2021 21:51:16

Versaboss13/04/2021 16:28:11
470 forum posts
51 photos

So, finally I did it. The cocks came out quite well I think (but far away from Clive's works). I did not check if they are tight, but anyway they are more a decoration on a small Stuart 10H.

img_20210409_170058.jpg

Regards,
Hans

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