Brass

[willofiam]

I thought I would bring up the topic of brass, can be a bit confusing, by no means do I have all the answers nor did I pay much attention in science class.
Why do we use brass in clocks? Low friction, high corrosion resistance and high tensile strength.

Brass is made up of a combination of copper (Cu) and zinc (Zn). Depending on the percentage of copper and zinc determines brasses properties and application. Now, to make it a bit more confusing, lead (Pb), (usually somewhere around 1-3%, can be introduced to the alloy for machine-ability purposes).

Reading about types of brass in some of our horological books I have found references to a brass that I did not find in the USA. Looking into it a bit further I realized the #'s refer to types of brasses found on the European side of the world, numbers like CZ121 or CZ120 ect...
Here is a bit of what I am finding;
CZ120 = 59% copper, 39% zinc, 2% lead
CZ121 = 58% copper, 39% zinc, 3% lead

Now, over here in the US I see #s like C360 or UNS C36000, C260 or UNS C26000, C385 or UNS C38500.
Here is a bit of what I am finding comparable to the CZ brasses;
UNS C360 = 60% copper, 37% zinc, 3% lead
UNS C377 = 58%-60% copper, 39% zinc, 1.5%-2.5% lead
UNS C385 = 58% copper, 39% zinc, 3% lead

Color of a brass may also be a determining factor of what to use especially when doing a restoration on a older clock
(wanting it to blend in) The term "yellow brass" from what I understand is an American term that refers to a typical 33% zinc brass.

O.K. thats a start, to mention other brasses we still have CZ124, c35300(engravers brass) to look at...and there are so many more..

Here is a question....how can you find out what type of brass you may have when you do not know for sure what type it is?

...if you have any input or experience with brass let us know.

[Bernie Weishapl]

Great subject William and it will be interesting to see where this goes. I think I have all three which is the 360, 377, and 385. I have never delved into the why's, what's and composition's.

[willofiam]

Hey Bernie, do you remember where you got your brass? I have been trying to find a good supplier with reasonable prices.

Also, I found some good information on how brass is made, "how products are made" volume 6. There is ssssoooo much out there on brass.

Looking into the c35300 brass and finding this to be a good brass to use in clocks, I may have been a little wrong in saying c353 was an "engravers" brass, but I have heard of it being called that.

c35300 brass = Cu 60-63% Pb 1.5-2.5% and remainder is Zn = approx 36.5% Also appears Fe (iron) can be added = .10% max. Iron makes the brass harder and makes the internal grain structure smaller so that the metal can be shaped by repeated impacts in a process called forging. There are different hardness's = annealed, 1/4 hard, 1/2 hard, 3/4 hard, hard, extra hard and spring.

1/2 hard c35300 looks to be a good brass for clocks, any thoughts?
William

[Bernie Weishapl]

William I am not sure. I bought it about 20 yrs ago. I got several strips of each 4" wide and 2' long. Some were 12" X 12" squares. Over the years I have only used about half of it. I think I got it from McMasters but not sure. They used to carry flat brass along with Enco. Not sure if they do today or not. I looked at the tags on what I have left and they are 353, 360, 385. It was a lot cheaper 20 yrs ago than it is now. I know the brass rod which is 1/4" X 6' I bought back then was like $4 and now it is like $13. Anyway sorry I couldn't be of more help. I bought a lot of that flat brass, brass rod, and steel rod as I was going to build a clock but kids and my job got in the road but it has been good because I have had plenty of metal for making parts. Good intentions just not enough hours in the day.

[willofiam]

[Bernie Weishapl]

Not sure if 36 hrs would even do it.