GG,

This is not a scientific study (low sampling number, etc), but
I was supervised by an engineer and the machine is accurate to
±1 Hardness Rockwell C. Just for the heck of it...
The numbers stated are from the average of 3 readings. If other
Galoots have data for legendary outperforming tools, for other
time periods,  please send them in for comparison.
Or, you could always send me your infill for testing... ;-)

Plane irons                                       HRC
 Record #7 T14 Tungsten steel, laminated          63.2
 Stanley #4 SW laminated                          62.6
 Stanley #5 SW laminated                          62.3
 (Rev. Hock says 62 for his blades)
 (LN states 60-62)

Saws
 No.7 Disston Philada                             48.5
 D8 Disston Philada                               44.0
 No.12 Disston Philada                            48.5
 #4 Backsaw Disston Philada                       48.9
 Bow saw blade, no mark, 24 x 1 in.               52.0
 (3 for $1.50, drive by...)
 (LN Ind. dovetail saw suppose to be 52)

Chisels
 Marple Blue Chip                                 58.8
 TH Witherby Warranted bevel edge                 62.4
 Stanley #720                                     60.8

#66 beader blades
 orig. Stanley reeding                            54.5
 LN router blade                                  62.0

#45 blades                                   62.1-63.2
#46 blades                                   63.5-63.7

EC Atkins No.5 scraper blade                      51.4

When I told him the age of some blades we were testing,
the engineer was impressed at the hardness attained.
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 didn't know better...

Louis Michaud

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

I have a good, old, Wilson, WWII vintage, accurately calibrated hardness
tester and would be happy to test anything that comes this way (as long
as you some green for the return UPS... )

Flat, parallel surfaces will yield the most accurate results and the
item must be thick enough for the test to work. Also, we'll get poor
results from things surface hardened, plated, or otherwise surface
treated.

I did some tests some while ago of old Satanley blades, etc. but I had
the problem of the laminated blades. In order to test the hard "bit", I
would have had to put the little test dimple in the back of the blade
and I didn't want to do that. Be advised and if needed recommend a
suitable test location on the piece.

Also, please note that hardness alone does not a good tool make. There
are several other constituents that can make or break (literally) a
tool. Alloy, hardening process, hardness, sharpness all have to be right
for the thing to work.

(There's a joke or two in all this hardness talk.)

The Never-Wrong Reverend Ron

> 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?
>

Hi Gene & even-tempered Galoots !

Gene remarked on the brittleness of a Disston saw
whose hardness was in the neighborhood of Rc52.

Small wonder.  Except for the shock-resisting
tool steels (the S series) one should never
harden & temper a tool steel in the temperature
range that gives a Rockwell C hardness in the
mid-fifties.  That's because the steel will have
its worst possible combination of hardness and
ductility.  In other words, it will be brittle.

Therefore, tools which have to end up in the mid fifty
Rockwell C range must be made from S series tool steels,
or they must be lower in carbon so that they end up
in that range after tempering at lower temperatures.

The so-called temper-embrittlement range is around
500 degrees Fahrenheit.  The S series tool steels
don't drop to the mid-fifties in hardness unless
they're tempered considerably hotter than that, so
they don't get brittle.

Saw steel will therefore perform better if tempered
into the mid forties on the Rockwell C scale.

Galoots whose saws become brittle after electrolysis
can prevent that by baking the saws around 300 F for
several hours immediately after the electrolysis to
drive off the hydrogen that causes the embrittlement
(actually, delayed cracking due to residual stress).

A saw whose teeth have already cracked due to omission
of the post-electrolysis baking step will have to have
all those teeth "pulled" and replaced with new ones
filed from the solid.

Without seeing the broken teeth first-hand, I can't say
which malady did in that Disston, so I've given both of
the sad explanations.

Best regards,
George Langford
amenex@a...

Gene, Rev. Ron and Galoots,

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

3 whacks at 1 spot on 1 sample. Average the 3 tests and that's
1 reading. Then we took other readings on different areas of the
sample. Eliminated highest and lowest, averaged the rest and that
is the number given on the list.

For the thin saw material, we did a Superficial N test. It still
uses a diamond point but loads to 15 kg instead of 150. I gives
the hardness only at the surface. A chart converts the N numbers
to HRC. On thick saw blades (7, D8) there is no difference between
HRC and N. On the thinner material HRC tends to be inconsistent.

On the laminated plane blades, the readings were consistent over
the lenght of the hardened steel. Elsewhere it fell to 15 HRC
(or lower) which is considered unreliable and off the scale.

The saws had an even hardness. 3 tests on one spot done on 4
different areas of the same sample. The average of the 3 tests
varied only by 0.3 HRC from one area to the other. The D8 had
higher variance but I don't have the numbers here.

Hardness on the chisels usually went down to 50 HRC about 1 3/4
in. from the tip and then even lower.

>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.

I took out some set on the bow saw blades at 52 HRC by pressing the
blades in a steel vise. It responded well without any snaps. After
sharpening, the resulting set was sufficient. I'll see when I have
to set the teeth again...

>Also, please note that hardness alone does not a good tool make. There
>are several other constituents that can make or break (literally) a
>tool. Alloy, hardening process, hardness, sharpness all have to be right
>for the thing to work.
>
>The Never-Wrong Reverend Ron

I did these tests only to get a general idea of the hardness for
different tools/application. I don't consider an HRC number to
indicate a quality scale. Hardness is only -1- parameter.
I also hoped to get feedback on the variability just for the fun
of comparing.

Bon rabotage,
Louis Michaud

Thankyou to George Langford & Rev.Ron for adding to the info being absorbed
by this sponge-brain.

Even tho the blade I was talking about had never been zapped, with lots of
Galoots now dumping saws into zap-tanks, one of George's comments bears
repeating:

>Galoots whose saws become brittle after electrolysis
>can prevent that by baking the saws around 300 F for
>several hours immediately after the electrolysis to
>drive off the hydrogen that causes the embrittlement
>(actually, delayed cracking due to residual stress).

Sometimes things didn't work out just right at the factories, but we are
more fortunate than they were, having Ron and George and others willing to
help.

Gene  (Disston would have paid them for their help dontcha think?)  :>)

On Fri, 18 Jun 1999 19:51:06 eugene@t... writes:
>Thankyou to George Langford & Rev.Ron for adding to the info being

>>Galoots whose saws become brittle after electrolysis
>>can prevent that by baking the saws around 300 F for
>>several hours immediately after the electrolysis to
>>drive off the hydrogen that causes the embrittlement
>>(actually, delayed cracking due to residual stress).
>

Oh yeah, that reminds me of a question I forgot to ask:

Does this mean that just letting the saw sit around for
a week or so before using, or setting it in the sun al say
will be inadequate to prevent cracking?