Don Malling wrote:
> There were some questions about how Cams and Lifters were hardness
> tested, so I asked Steve Gruenwald, owner of Integral Cams, how they did
> it.
>
> His reply:
>
> Dear Don:
>
> We use a Rockwell hardness tester to hardness test the lifters. It
> creates a small pin mark in the lifter face. When we regrind the
> lifters sometimes this pin mark cleans up before the other wear marks
> and sometimes not. It depends on how bad the lifters are worn.
> Rockwell hardness checking is generally classified under "destructive
> testing" but its not literally that brutal and in this case it only
> means that the part can't be used "as is" after testing. We certainly
> would not want to hardness check the lifters after grinding and
> polishing them because the little pin mark would cause rapid cam and
> lifter wear in an engine. So the only bad thing about this testing
> method is that we can't test an already new set of lifters without
> having to regrind and polish them afterwards. Another question I am
> often asked is: when we regrind the lifters to make the pin mark go
> away, are we grinding off the hardness layer and will the lifter now be
> soft? The lifters are chill cast which has a broad diffused hardness
> band so we don't have to worry about instantly grinding through the
> hardness band like you would if the lifters were induction hardened.
Although somewhat more expensive to purchase than a Rockwell Hardness Tester, a
microhardness tester is the instrument of choice for non-destructive harness
testing. It uses either a Vickers (square cut) diamond, or better yet a Knoop
(oblong 1:7) diamond indenter instead of Rockwell's steel ball to make a
microscopically small indent. The dimensions of the indent are measured using
the
built in microscope, and are so small that when done properly, the tested item
can be returned to service as is.
Jim (the dad)
microdoc@zoominternet.net
1960 MGA 1600 Very Red
1974 MGB-GT Damask (Very Burgundy) Red
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