Sorting brasses and bronzes etc.

Edited By Colin G on 11/02/2012 19:56:52

Hi Colin, not the easiest thing to do if you are inexpearienced but a few pointers are as follows:-

Brass is fairly easy and if you machine it it will cut with fine swarf that is in small pieces

Gunmetal, look at the bar it usually has a slightly speckled appearance -- not definative only a guide, it is generally softer than brass and adifferent colour

Bronze is a coppery colour but much harder than copper

Ally bronze, almost identical in colour to Admiralty brass -- nice yellow colour but it is much harder to machine and the swarf comse off in spiral or contiuous string [assuming you are not using a chip breaker] The outside of the bar willl probably not show the oxidation associated with brass.

Beware of Aluminium bronze it generally does not make good bearings but it is highly corrosion resistant.

Hope this helps a little

John

I was given a 6ft length of 3/4" dia. rod, the man said it was "electrical brass". I can find no references for this, I've been using it for general purposes, spacers etc. but would like to know if it is anything special, it machines much like ordinary brass but maybe a bit tougher. It did origenally come from an electrical wholesaler. Any ideas?

Thanks to JohnF for your reply to my question. It was interesting to see that you were the only person to be able to give a response when it has had over 500 viewings. If anyone can add to your answer then please do not be shy! So thanks again John.

Colin G.

As John said, it is not easy.

Brass consists of an alloy of copper and zinc sometimes with a bit of lead to make machining easier.

Bronze (which includes gun metal) is primarily an alloy of copper and tin but usually with some zinc and other metals added.

One test John hasn't mentioned is to put a drop of hydrochloric acid on it and look at the colour change. Brass will go pink. Bronze will still change colour depending on the amount of zinc present but will be paler.

Short of a full chemical analysis if you have a critical application it is safest to buy known new material.

Russell.

Hi, Colin,

I'm not surprised at the lack of informed response - I asked much the same question in the forum something like a year ago - and gots lots of hypotheses, but no real answer - the metal I wanted to identify was eventually chucked into the 'odds and sods' bin, and the project is suspended until I can get hold of suitable material.

Hi, Colin,

Some more info - try googling 'identifying brass and bronze' - ther is some useful info there, e.g http://eurekaifoundit.us/antique/metals.html

I dont think there is a generic answer to this question as there are many many types of bronze!

In the 60's I spent many years in the copper industry where we made copper alloys and bronzes and in most case the only quick way was for our sampler to drill a piece and he could usually tell what the generic alloy was. He accomplished this by drilling into the sample with a half inch drill in a drill press. If the sample was brass then the colour would show the alloy and the hardness if it was a bronze but only analysis could definately determine the alloy.

Although some brasses with high tin as an impuruty would be as hard as nails so the drilling would fail but in the end analysis is the only true way.

You can now get hand held xray fluorescence machines that will show the alloy, a bit out of HSM range cost wise.

Sorry for the pessimistic tone but it really is a mine field on alloy determination.

see link http://www.spectro.com/pages/e/p010602_spectro_xsort_video.htm

Peter

Edited By peter walton on 16/03/2012 18:34:18

Late answer I know but this is the gospel - there is no sure way to visualy determine any metal grade.

You can send the material away for testing though I doubt it would be economic for most people.