OldTools Archive

Recent Bios FAQ

64154 eugene@t... 1999‑06‑17 Re: Some Rockwell C hardness numbers
At 09:33 AM 6/11/99 -0400, Louis Michaud  wrote:
Good things about Rockwell C readings, mostly snipped out now.

GG's
I haven't seen any comments on that post, but I have some questions.

Way back (quite a fur piece), I yacked about a Disston 12 I found broken
cleanly in half, no hint of bending first.  It also had several missing
teeth.  From the condition of the handle I guessed it had seen very little
use.  Wanting to make scrapers out of the blade, I was surprised how
difficult it was to cut up.  So I had it tested.

I don't know the calibrated accuracy of the machine being used, but it was
in the QC lab of a tap and tool manufacturer.  On that one we got 52
repeatedly (I would have guessed it was even harder).  Now, I'm sure
hardness must have varied a lot over the production years or batch to batch
with limited QC specs and methods.  But if many of Disstons saws performed
like this one, the complaint dept must have recieved a lot of nasty e-mail.

>This is not a scientific study (low sampling number, etc), ...
>The numbers stated are from the average of 3 readings. ...

Gotta ask: three whacks at one sample or tests on three samples?

Also, I think I remember both Rev. Hock and the Leachmeister doing larger
sample testing of old stuff and beta-testing .  Has anyone who might want
to comment checked anything?   Does it sort of fit in with Louis' results?

>the engineer...
>He was also surprised that the teeth of the saws could
>be bend with out breaking when the metal had a hardness
>of 48-52, ...  ...

I couldn't alter the set of any tooth in that #12 blade without hearing
that sickening little *snap* sound.

Gene



Recent Bios FAQ