"Dan Miller" wrote in message
...
I've been reading some "how to" books on making various lathe items and
often they call for FCMS (I believe this is Fast Cutting Mild Steel) and
MS (Mild Steel) and sometimes BMS (Bright Mild Steel) Some of these
terms may be specific to the UK. I'm always trying to get a nice mirror
finish on my projects so I stumbled across 12L14 alloy which was billed
as FCMS. It's a dream to work with but I'm skeptical about how tough it
is cuz it cuts like butter. Anyway, occasionally I'll see books call for
"unleaded" FCMS. The 12L14 Alloy definatlely contains lead. So.....Can
anywone clear this up for me?

12L14 is leaded. Its mechanical properties are quite good, somewhat
surprisingly. You can look them up on Google, and you'll find plenty of
comparisons.


Is there another leadless alloy of FCMS that cuts and gives a nice
finish but is tougher due to lack of lead??

Don't jump to conclusions about "toughness," just because it contains lead.
If you mean what engineers mean by toughness in steel -- impact strength, as
measured by notch- or Charpy testers, you shouldn't have much trouble
finding that on the Web, either.

There are other free-machining steels, used mostly in high-volume
production. They generally contain calcium, phosphorus, and/or sulfur.
They're no great deal in the mechanical-properties department, but they're
free of lead.

Is 1018 alloy basically accepted as MS ("Mild Steel").

In the US, it's anything from 1008 (sold mostly as sheet for stamping) to
1020.

Does anyone have a feeling for what US alloy might correspond to BMS?--

Not me.

how are its properties different from MS?
What are the machining properties of 4130? Perhaps this is the best
compromise between finish and toughness?

What is your application for the steel?

--
Ed Huntress