Forging brass; how easy would it be?

I have some round brass bar 50mm diameter and I need a disc about 53mm diameter (for a good fit) and about 10mm thick. Brass costs a bit and I was hoping to forge a 50mm disc from what I already have (around 13mm thick - to ensure there's enough volume)

I have raised copper cups in the past, using blanks of a few mm thickness and I know about annealing techniques. I would think my gas torch would be adequate and I will keep the work clean before bashing it.

I have a raising hammer but it is probably a bit light weight for the job so I was planning to clean up and shape the ball on a heavy ball pein. Working outwards from the centre in a spiral -two or three times- would seem the thing to do. It's not a big stretch if I anneal it each time.

I will radius and face the result and then solder it to a smaller diameter bar.

Can anyone suggest anything that I may have not mentioned? It seemed well worth a punt and at least it would be another 'experience'. Is brass problematical for forging?

Andrew Lyner

You can search Google as well as I can, and it suggests that forging is a standard way of forming brass components.

This is a link to a video about making a Japanese sword guard by a superlative metalsmith called Ford Hallam......entitled; "the search for Katsohiro's tiger".......It's well worth watching by anyone who makes stuff in metal whatever the discipline or purpose...

https://www.youtube.com/watch?v=wGMj7o6AwnM

In the video he casts a disc of copper and silver alloy and then beats the disk using hammer and small anvil.....you should watch that part of the video as it will tell you exactly how to do wha tyou want to do.

Just be careful when forging brass 'cos some grades suffer from 'Hot Short' if heated too much and then worked. In a nut shell it will crumble and flake (like short crust pastry).

Guy

If you soften (anneal) the brass it should be easy to squeeze out a 50mm disc to over 53mm, using a hydraulic jack, for example.

Tim

Edited By Tim Stevens on 09/07/2019 23:12:42

Thanks for the ideas guys. My particular problem is easier to solve than sword making - should be easier than my experiences of raising copper cups, too because the change is diameter is only a few percent.

The hydraulic jack suggestion is interesting. I might look round for a friendly machine shop press if you reckon a jack would do the job.

One factor is that I want to avoid having to 'make good' as much as possible and some nicely controlled force would probably avoid the disc shape changing too much.

It wouldn't;t be a total disaster if the work was a write off as I could always just buy some more. Though 50mm diameter seems to ne the biggest that easily obtainable and not too expensive.

Find someone with a BIG fly press. You would want to give it one big thump as it will quickly work harden.

Edited By Speedy Builder5 on 10/07/2019 06:30:03

Do you know what grade of brass it is, the softer "bending" brasses would be better but as it is rod I think you are more likely to have hard brass

Life's to short and the gas will cost near as much as an offcut. I would just buy a piece. I often see small offcuts at the motorcycle autojumbles and shows, I will check my stock I may even have a piece, where are you ?

I was on the Metals4U site and I had a quick look, they will supply a 25mm length of 2.1/8" (54mm) for £12.70, 50mm length for £25.

You may just want to have a go at the forging excercise of course.

I can echo the words of others on this one after my experience in making car radiator top and bottom tanks from brass sheet.

I had done some google searches and read the books but even so the best advice came from a particularly skilled and experienced engineer who was aware of the pitfalls of the wrong grade of brass and the limitations of the home workshop. My first attempts were pitiful but with his advice I succeeded.

Beware overheating the brass , when it goes crystalline it is scrap.

I was shown to use soap rubbed onto the surface and heat until the soap turns brown.

My (sadly now deceased) friend's advice was to press or draw the material if possible as hammering work hardens it so quickly.

Do not be put off from having a go - actually trying it is part of the fun and adds to your knowledge and skills.

Posting your question here helps others like me to learn also.

I never cease to be amazed at the breadth and depth of skills and knowledge held by members and so generously shared with fellow enthusiasts.

Edited By John Paton 1 on 10/07/2019 09:19:35

If it's brass bar, then it's probably CZ121, in which case you've little chance of forming it as you want to do. It just doesn't anneal like brass sheet and stays hard after you've heated it. You can usually anneal the generally-supplied grades of sheet. Mostly due to the zinc content!

Just try it out on a small piece of brass rod first - so you don't waste both gas and brass - and after bopping it cold, try battering it hot, to see what Guy Lamb means about it being "hot short". Phosphor bronze rod can behave similarly.

Turn it. If the turnings come off as a spray, go to Metals4u and save the planet from greenhouse gases.

Regards Ian

Edited By Circlip on 10/07/2019 11:03:14

The problem is that offcuts of 'large' stock are not much use to me and each time I just go to Metals4U it ends up costing me more than I expected and it is largely wasted money. It's just a matter of priorities. I will look for a local blacksmith with a damn good fly press.

Also, I love to try things and forming metal is very satisfying when it works. I made a lot of Silver and Gold jewellery, way back, and that was really satisfying (more often than not).

The general bank of knowledge on this forum is very impressive.

Andrew, I have looked at my stock and have nothing over 2" for you. The 2" piece I found is about 3 1/2" long and has still got the price on in felt pen. £3 I usually pick up useful bits and bobs from the bike shows. Chris.

I'd make a simple mould and cast a disc from offcuts and bar ends.An old stainless flask cup will function as a flask and last for a single melt.

I've used borax as a flux to stop the zinc catching light but apparently a tiny amount of aluminium (0.15 too 0.35%) added helps too (not more or you end with a nasty aluminium bronze - don't ask!)

Neil

Thanks for looking!

Some years back, I visited a place on a club visit. They were making brass fittings like the ones used with LPG bottles. They had a whole lot of power presses. The pieces of bar stock were being heated up with gas burners, and the press operator would pick one up with the tongs and put it on the lower die. He would hit the pedal, the upper die would come down and go back up, and a nicely shaped piece would then be extracted from the die. This worked well enough to reproduce letters on the finished piece, eg the makers name or whatever. It all looked pretty straightforward. I suspect the main things you would need to be concerned about would be whether the brass you had was a suitable grade, and then getting a suitable temperature, hot enough to soften it but not so hot as to make the brass hot short. I don't think work hardening is a concern if the brass is hot.

John

I find the Workshop Practice Series excellent for questions like this. № 30 is 'Workshop Materials' and it has much to say about Brass, buy the book! Edited highlights:

• Much depends on the type of Brass. Some alloys are better suited to hot working than others. In addition to different alloys being available, brass is sold in 'soft', 'quarter', 'half' or 'fully' hard condition. (Soft brass could be hammered usefully first without heating, hard brass cannot.)
• In the book only Naval Brass and the very similar Muntz Metal are associated with hot forging.
• It is easy to overheat brass, 400-600℃ (dull red in subdued daylight) for a short time is enough to anneal it. Overheating weakens the metal, which may be a concern if the strength of the new disk is critical. (So does beating hard brass, because it's brittle.)
• Being copper based, brass absorbs a lot of heat, ie relatively expensive to get up to temperature compared with steel.

Comment:

The book implies to me that most Brass is worked carefully cold or hot rather than forged to avoid damaging the metal. The most usual approach is to soften the brass by annealing, then hammer cold or as it cools down until it work hardens, then repeat annealing until the job is done.

I suspect Brass can't be beaten into shape like Iron or Steel simply by hitting hot plastic metal with a big hammer. Softening by annealing is a more subtle technique, but it might be easier to do in a home workshop lacking a forge. My guess is that the brass alloy used to make, say, plumbing parts is much easier to damage by overheating and work hardening than the type used for electrical components, while both are inferior to Naval Brass, with Naval Brass being markedly harder to forge than steel.

So I'd try the annealing method. Please let us know what happens whatever you try!

Dave

Copper (and brass) has a much lower specific heat value than steel. Easier to raise its temperature but it will conduct that heat away much more quickly.