DFX file

[francist]

Sounds like SAE 660 (C932) bearing bronze, aka "rotocast". It has characteristic helical marks on the outside from the continuous casting process, almost like a faint tiger stripe sometimes. I know continuous casting is just a process and there are possibly a number of metals cast that way, but 660 is definately one of the more popular ones. At the foundry here you just ask for "rotocast" and they know you're after 660.

It is beautiful stuff to work, I've made a number of replacement lock parts from it.

-frank

 

[PeterT]

I don't suppose you have any ideas on how to identify which bronze alloy I have? I have a chunk that was bought from the scrap dealer as brass and when I picked it up to use last week I then realized it was bronze not brass. It turns beautifully on the lathe. It has the faint casting rings on the outside of the material. I'm guessing "bearing bronze".

Good score. About the only way I can think of is those graduated hardness testing 'file' sets (for lack of better description). If the file scratches, the material is softer, So you can bracket it within the range & get some idea. C932=SAE660 is 65 Rockwell B. C544 (phosphor bronze) is 82 RB.
*edit* I think I may have the wrong Rockwell scale. Dang internet! To be continued....

I doubt you have aluminum bronze but its harder still. They look like this. Very useful but kinda spendy. I don't have them, but Stefan shows them in use all the time. But he does a lot more heat treating & machining weird stuff.
https://www.amazon.ca/Fowler-52-760-000-Hardness-Tester-Diameter/dp/B00B5HQYAM

Those spiral rings - I'm not sure are the definitive tell-tale sign of 660 vs. I've heard more than a few times guys picked up the wrong bronze stick. Some have faint spirals which can be misinterpreted. I'll try & remember to take a pic of my C544. I dont have a lot of bronze experience. Just 544 & bit of SAE 660

 

[PeterT]

I can see now that some of my original data sources were wanky. Good that we were talking about this.
This site seems to be more consistent http://www.matweb.com/index.aspx

Depending on the alloy, hardness can be referenced in Rockwell, B, C, F, Brinell... so you have to be careful to watch the units & only compare apples to apples. I put the bronzes & brass on Rockwell B just for comparative reference.

I never paid attention before but those hardness files are Rockwell C.
Now it makes more sense to me why 932 (SAE-660) seems so sticky to drill by comparison to other bronze.

 

[DPittman]

I can see now that some of my original data sources were wanky. Good that we were talking about this.
This site seems to be more consistent http://www.matweb.com/index.aspx

Depending on the alloy, hardness can be referenced in Rockwell, B, C, F, Brinell... so you have to be careful to watch the units & only compare apples to apples. I put the bronzes & brass on Rockwell B just for comparative reference.

I never paid attention before but those hardness files are Rockwell C.
Now it makes more sense to me why 932 (SAE-660) seems so sticky to drill by comparison to other bronze.

Thanks for the info, I hadn't looked in to it but I was surprised to see such a range in hardness levels in bronze material.

For those who haven't seen the bronze rings that appear in some cast bronze stock, the chunk I have shows it very predominantly. Here is a picture of it beside some brass 360. When they are side by side the color difference is quite obvious

but when you are looking at just one dirty/oxidized piece on its own it can be more difficult to identify.