Quote Originally Posted by duskylim View Post
Sir:

Because they are made from engineering grade, case-hardening steels, the cams on the camshaft are themselves only brittle on their SURFACES (up to the depth of the case), and not THROUGH-HARD (hard all the way down to the core) as would be the case if they were made from heat-treated TOOL STEELS.

In a case-hardening steel, the hardness extends only up to the case-depth - an outer skin of high hardness typically 0.5 to 1.5 mm thick at most, that has been treated to have a high carbon content.

The rest of the underlying material down to the core is tough and shock resistant - a very desirable combination of properties for an engineering and machinery steel.

The steels I mentioned previously are typical for car parts and machinery of this nature and usage.

AISI (American Iron and Steel Institute) 4140 or 4340 are chrome-molybdenum and chrome-molybdenum-nickel steels with 0.40% carbon respectively - they are a good example of engineering and case-hardening steels.

High Speed steel is an entirely different class of TOOL STEELS used where high hardness, strength and dimensional stability after heat treatment is desired.

High Speed steels are generally not used in automotive or machinery applications mainly due to high cost - they are very expensive steels, and the design requirements can be met by general-purpose, moderate cost, engineering and case-hardening steels.

Going back to your camshaft, like I said before, only the cams themselves are hardened, the rest of the camshaft was not carburized (treated to absorb a large amount of carbon into the steel) and thus is not hard, but rather is tough.

That applies to the bearings and the rest of the shaft - this is the part that Dieseldude said could have BENT.

A good machine shop will put the cam on a set of V-blocks and mount a dial-indicator near it to measure the straightness and runout.

You cannot see a mis-alignment of a few thousands of an inch (few mils) by eye - you need the dial indicator and the correct set-up to do it.

Having made tool-and-die, plastic moulds and semi-conductor tooling, I have extensive work and professional experience with special steels, metrology and precision machining.

Best Regards,

Dusky Lim
ok, so what you mean is that cracking is not a possibility but bending is?