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· thhhpptthh!
47,371 Posts
"Custom machined from chrom-moly and stainless steel these brutes are greasable, rebuildable, and feature adjustable pre-load. "

but from the chart - "evolution - 4140"

so which is it?

· Registered
6,518 Posts
Discussion Starter · #5 ·

4140 is chrom-moly (one of them)

From my steel article:

Alloy steels are also designated using a standard four digit numbering system, very similar to that used for the carbon steels. However, the first two digits indicate the major alloying element or elements, whereas the last two digits again indicate the approximate carbon content of the steel in tenths of a percent. For example, SAE 4340 contains approximately 0.40% carbon. The first two digits of an alloy steel's designation indicate the alloying elements and their percentages as follows:

13xx - Manganese-1.75 %
40xx - Molybdenum-0.20% or 0.25%
41xx - Chromium-0.50%, 0.80% OR 0.95% PLUS Molybdenum 0.25%
43xx - Nickel-1.83% PLUS Chromium 0.50% or 0.80% PLUS Molybdenum 0.25%
44xx - Molybdenum-0.53 %
46xx - Nickel-0.85% or 1.83% PLUS Molybdenum 0.20% or 0.25%
61xx - Chromium-0.60% or 0.95% PLUS Vanadium 0.13% or 0.15%
86xx - Nickel-0.55 % PLUS Chromium 0.50% PLUS Molybdenum 0.20%
87xx - Nickel-0.55% PLUS Chromium 0.50% PLUS Molybdenum 0.25%
88xx - Nickel-0.55% PLUS Chromium 0.50% PLUS Molybdenum 0.35%
92xx - Silicon-2.00%

Note that the hugely popular designation "Chrom-moly" steel has nothing to do with the shiny stuff on bumpers and hubcaps, but is in fact a reference to the fact that the steel in question has major alloying elements of Chromium and Molybdenum. That's why I prefer to write the abbreviation as Chrom-Moly, without the "e" on chrome. It is also popularly abbreviated as Cr-Mo, Cro-Mo, etc. Note that 41xx and 43xx alloy steels can and frequently ARE both refereed to as "Chrom-Moly Steel", though obviously the 43xx also has significant Nickel added.
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