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Default Case hardening ...

Many years ago, my brother in law, who was a mechanical engineer /
toolmaker, gave me a bag of 'case hardening powder', which I still have.
Does anyone know what exactly this stuff is (it's white, and if the police
got hold of it, I'd probably be locked up whilst they determined just what
it was ...) and how to use it ? I got to thinking about it today, when I was
stoning the edge on a chisel ready for use tomorrow on a job. It occurred to
me that once the original factory edge has gone from a wood chisel or plane
blade or whatever, and you've resharpened it, it never seems to last as long
again as it originally did. Is this because they harden the edge when it's
made ? Is it appropriate, or even possible with home DIY facilities, to
harden the edge once it's been restored ?

Arfa

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Default Case hardening ...

On 19/06/2010 17:47, Arfa Daily wrote:
Many years ago, my brother in law, who was a mechanical engineer /
toolmaker, gave me a bag of 'case hardening powder', which I still have.
Does anyone know what exactly this stuff is (it's white, and if the
police got hold of it, I'd probably be locked up whilst they determined
just what it was ...) and how to use it ? I got to thinking about it
today, when I was stoning the edge on a chisel ready for use tomorrow on
a job. It occurred to me that once the original factory edge has gone
from a wood chisel or plane blade or whatever, and you've resharpened
it, it never seems to last as long again as it originally did. Is this
because they harden the edge when it's made ? Is it appropriate, or even
possible with home DIY facilities, to harden the edge once it's been
restored ?


Chisel blades are made from carbon steel that is hardened by heating to
cherry red heat and plunged into water, or oil to harden it. After this,
the blade is heat treated again until it goes blue and cooled again.
This makes the whole blade hard enough to take a good sharp endge. Where
you might be failing is in not getting a good edge by not using a
suitable sharpening stone and ending up with rough cutting edge that
wears very quickly.

Moving on to the case hardening powder you have, this will consist of
animal bones. The same carbon which was added to cutting blades when the
steel was made. This carbon is distributed all the way through the
steel, unlike case hardening that is only skin deep and is no use for
hardening anything, unless it only requires a skin hardnes adding to it

Dave
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"Arfa Daily" wrote in message
...
Many years ago, my brother in law, who was a mechanical engineer /
toolmaker, gave me a bag of 'case hardening powder', which I still have.
Does anyone know what exactly this stuff is (it's white, and if the police
got hold of it, I'd probably be locked up whilst they determined just what
it was ...) and how to use it ? I got to thinking about it today, when I
was stoning the edge on a chisel ready for use tomorrow on a job. It
occurred to me that once the original factory edge has gone from a wood
chisel or plane blade or whatever, and you've resharpened it, it never
seems to last as long again as it originally did. Is this because they
harden the edge when it's made ? Is it appropriate, or even possible with
home DIY facilities, to harden the edge once it's been restored ?

Arfa


Could be made from animal bones - rich in Carbon.

The concept is to raise the steel to a certain temp at which it can absorb
the carbon from the powder. This gives a low carbon steel a high carbon
outer layer. The steel is then reheated and quenched to harden it. The inner
core remains a low carbon softer steel. It is likely that a chisel is made
from a high carbon steel so "carburizing" it with this powder would have no
effect.

http://www.tpub.com/content/aviation.../14018_665.htm



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"Arfa Daily" wrote in message
...
Many years ago, my brother in law, who was a mechanical engineer /
toolmaker, gave me a bag of 'case hardening powder', which I still have.
Does anyone know what exactly this stuff is (it's white, and if the police
got hold of it, I'd probably be locked up whilst they determined just what
it was ...) and how to use it ? I got to thinking about it today, when I
was stoning the edge on a chisel ready for use tomorrow on a job. It
occurred to me that once the original factory edge has gone from a wood
chisel or plane blade or whatever, and you've resharpened it, it never
seems to last as long again as it originally did. Is this because they
harden the edge when it's made ? Is it appropriate, or even possible with
home DIY facilities, to harden the edge once it's been restored ?

Arfa


http://en.wikipedia.org/wiki/Carburizing

http://en.wikipedia.org/wiki/Case_hardening


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"Arfa Daily" wrote in message
...
Many years ago, my brother in law, who was a mechanical engineer /
toolmaker, gave me a bag of 'case hardening powder', which I still have.
Does anyone know what exactly this stuff is (it's white, and if the police
got hold of it, I'd probably be locked up whilst they determined just what
it was ...) and how to use it ? I got to thinking about it today, when I
was stoning the edge on a chisel ready for use tomorrow on a job. It
occurred to me that once the original factory edge has gone from a wood
chisel or plane blade or whatever, and you've resharpened it, it never
seems to last as long again as it originally did. Is this because they
harden the edge when it's made ? Is it appropriate, or even possible with
home DIY facilities, to harden the edge once it's been restored ?

Arfa


Be very careful - it could be Cyanide




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Default Case hardening ...



"Arfa Daily" wrote in message
...
Many years ago, my brother in law, who was a mechanical engineer /
toolmaker, gave me a bag of 'case hardening powder', which I still have.
Does anyone know what exactly this stuff is (it's white, and if the police
got hold of it, I'd probably be locked up whilst they determined just what
it was ...) and how to use it ? I got to thinking about it today, when I
was stoning the edge on a chisel ready for use tomorrow on a job. It
occurred to me that once the original factory edge has gone from a wood
chisel or plane blade or whatever, and you've resharpened it, it never
seems to last as long again as it originally did. Is this because they
harden the edge when it's made ? Is it appropriate, or even possible with
home DIY facilities, to harden the edge once it's been restored ?


You are probably overheating it if you are using a grinder to sharpen it.

Arfa


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Default Case hardening ...

On 19 June, 19:24, "dennis@home"
wrote:


You are probably overheating it if you are using a grinder to sharpen it.

Which is the reason why it preferable to use a low speed wheel to
sharpen a wood chisel or plane iron before honing it on an Arkansas
stone or similar. Once overheated it is almost impossible for the
average DIYer to restore the correct temper to the chisel/iron.
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Default Case hardening ...

On 19 June, 17:47, "Arfa Daily" wrote:
Many years ago, my brother in law, who was a mechanical engineer /
toolmaker, gave me a bag of 'case hardening powder', which I still have.
Does anyone know what exactly this stuff is (it's white,


No idea. Never heard of the stuff - in white at least.

Kasenit is the usual case hardening powder. Greyish, maybe describable
as light brown , and stored in tins because it doesn't enjoy
moisture. It's very easy to use.

Cyanide hardening compounds are (IMHE) supplied in pellets, not as
powders (or made up in solution) - again because of moisture. They're
safe enough to handle (keep away from moisture and especially acids),
but they are a hazard to work with. Like cyanide electroplating
solutions, they're beyond most home workshops.

The only common white workshop powder I can think of would be silver-
soldering or brazing fluxes - fluorides.


Case hardening is best used to make mild steel components more wear-
resistant. It's a poor way to make cutting tools. It's also a poor
steel metallurgically, and as good steels are cheap these days, you're
better making tool edges from the good stuff directly.

The powder itself is a secret recipe that has changed in the last few
years anyway. It's broadly a mix of a carbon donor (hoof and horn, but
_not_ bone) and also a carbon dioxide donor (barium carbonate),
possibly also a nitrogen donor, i.e. a cyanide.

If you have case-hardening powder, there are two ways to use it. The
best way is to pack piece and powder into a sealed iron box, then
roast the lot in an oven for some time. No-one does this. People who
used to do it commercially, now use liquid baths instead. The workshop
way is to heat up the workpiece to a dull red, then immerse it in the
tin of powder and leave it to cool. Repeat for deeper diffusion. Avoid
the fumes. Then harden and temper the workpiece as for a higher carbon
steel.


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On 19 June, 18:25, dave wrote:

Moving on to the case hardening powder you have, this will consist of
animal bones.


No bones in it - hoof and horn instead.

Bone is a poor carbon donor and a good phosphorus donor, which is
generally a bad thing in steels.
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"Andy Dingley" wrote in message
...
On 19 June, 17:47, "Arfa Daily" wrote:
Many years ago, my brother in law, who was a mechanical engineer /
toolmaker, gave me a bag of 'case hardening powder', which I still have.
Does anyone know what exactly this stuff is (it's white,


No idea. Never heard of the stuff - in white at least.

Kasenit is the usual case hardening powder. Greyish, maybe describable
as light brown , and stored in tins because it doesn't enjoy
moisture. It's very easy to use.

Cyanide hardening compounds are (IMHE) supplied in pellets, not as
powders (or made up in solution) - again because of moisture. They're
safe enough to handle (keep away from moisture and especially acids),
but they are a hazard to work with. Like cyanide electroplating
solutions, they're beyond most home workshops.

The only common white workshop powder I can think of would be silver-
soldering or brazing fluxes - fluorides.


Case hardening is best used to make mild steel components more wear-
resistant. It's a poor way to make cutting tools. It's also a poor
steel metallurgically, and as good steels are cheap these days, you're
better making tool edges from the good stuff directly.

The powder itself is a secret recipe that has changed in the last few
years anyway. It's broadly a mix of a carbon donor (hoof and horn, but
_not_ bone) and also a carbon dioxide donor (barium carbonate),
possibly also a nitrogen donor, i.e. a cyanide.

If you have case-hardening powder, there are two ways to use it. The
best way is to pack piece and powder into a sealed iron box, then
roast the lot in an oven for some time. No-one does this. People who
used to do it commercially, now use liquid baths instead. The workshop
way is to heat up the workpiece to a dull red, then immerse it in the
tin of powder and leave it to cool. Repeat for deeper diffusion. Avoid
the fumes. Then harden and temper the workpiece as for a higher carbon
steel.



sorry - not bone - Hoofs and Horns.Cyanide was used in my Toolroom - as a
bath of molten cyanide salts. Provided a hard surface for gauging points ,
etc.. Not for cutting tools.




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"Arfa Daily" wrote in message
...
Many years ago, my brother in law, who was a mechanical engineer /
toolmaker, gave me a bag of 'case hardening powder', which I still have.
Does anyone know what exactly this stuff is (it's white, and if the police
got hold of it, I'd probably be locked up whilst they determined just what
it was ...) and how to use it ? I got to thinking about it today, when I
was stoning the edge on a chisel ready for use tomorrow on a job. It
occurred to me that once the original factory edge has gone from a wood
chisel or plane blade or whatever, and you've resharpened it, it never
seems to last as long again as it originally did. Is this because they
harden the edge when it's made ? Is it appropriate, or even possible with
home DIY facilities, to harden the edge once it's been restored ?

Arfa



It's quite amusing reading some of the comments about secret recipes of
potions and powders for case hardening, and for hardening and
annealing/tempering metals. Whilst not being by any means an expert - big
subject - I worked testing metals in a lab for a while, and actually had to
measure thickness of the case hardening on mild steel strip: we cut the
strip into randomly selected small sections, then encapsulated them in
perspex cylinders with a nifty hot press (also handy for making souvenir
coin etc key fobs) cut it in sections; polished to mirror finish; etch in
conc HCl or similar, and then inspect under microscope and measure dark
edge. Also had to try and measure hardness across the strips too -
measuring the diagonals of a square produced by diamond with weights
attached. Pain in the neck actually, and hard statistical work in the days
when a calculator was a curiosity only affordable by devoted Sinclair
fans... ah the little red lights... memories...

Anyhow, secret white powder you can all use next time to make a big hole in
a wall and don't want to pay out for a drill you only use once? You have it
by the kilo and it begins with S and ends in r. You got it. I'm surprised
nobody has mentioned the trick for putting water pipes through walls:
probably all spoiled rotten by power tools! Standard piece of iron water
pipe - prob should wear mask as often lead lined: cut a jagged end of rough
teeth on a length long enough to go through wall; blowlamp on end with said
teeth till red hot - or hot as it gets before the gas runs out; dunk
straight into pot of sugar, Lots of candyfloss smells and smoke and flames,
so not to be done near your petrol cans or old newspapers! Actually any
suitably coating carbon source will do, and old engine oil was also favoured
by some, but sugar works fine and I generally have a pot of it in the garage
for odd bits and pieces that want toughening. At a pinch you can even make
your own springs...

I found that a dunk or two in the sugar bowl enabled me to bore through a
cavity brick wall fairly neatly with the hammer and turn method similarly
used with the old rawplug tools. Probably not quite as neat as modern
drills, but such things were way beyond the pockets of mere mortals once
upon a time, before those wonderful Chinese people caught the capitalist
bug.

As for sharpening chisels and plane blades, it is quite hard to hold them at
the 25 or 30 degrees positions by hand (and for drills very mindboggling,
but you can get an eye for the angles in the end), but I have a very handy
little clamp on a roller made by Eclipse, that you clamp your chisel or
plane blade in; make sure the correct length is projecting for the angle in
question, and then you roll it up and down your series of oil stones until
all is razor sharp and satisfactory. Always start any job with sharpening
the chisels and plane blades: satisfying and saves on lengthy once in a blue
moon regrinds.

And while we are on blue. The hardness and temper of steels is of course
ultimately dependent on their composition: some can be so hard it is
difficult to find anything to cut them with once they have been heat treated
(skilled metallurgists can get a good idea of the composition/hardness by
looking at the colour of the sparks as they grind: not me). When grinding
with a grindwheel always have a pot of water handy and keep dunking. For
heftyish things like cold chisels dunk well before your fingers get hot or
you will make the end so brittle it just snaps off when you hit the other
end. With screwdrivers it's even more fussy as they heat up very quickly
and are easily ruined, and will either snap as soon as you turn them, or
twist like cheese (if it was only a cheap case hardened one). There are
tables of temper colours for different purposes 'straw' coloured tending to
be harder than 'blue' for example - but again varying with the metal. Straw
just at the tip, for cold chisels, and grading into blue behind, to give a
little bounce rather than snap...

Another v interesting subject...

S


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"Spamlet" wrote in message
...

"Arfa Daily" wrote in message
...
Many years ago, my brother in law, who was a mechanical engineer /
toolmaker, gave me a bag of 'case hardening powder', which I still have.
Does anyone know what exactly this stuff is (it's white, and if the
police got hold of it, I'd probably be locked up whilst they determined
just what it was ...) and how to use it ? I got to thinking about it
today, when I was stoning the edge on a chisel ready for use tomorrow on
a job. It occurred to me that once the original factory edge has gone
from a wood chisel or plane blade or whatever, and you've resharpened it,
it never seems to last as long again as it originally did. Is this
because they harden the edge when it's made ? Is it appropriate, or even
possible with home DIY facilities, to harden the edge once it's been
restored ?

Arfa



It's quite amusing reading some of the comments about secret recipes of
potions and powders for case hardening, and for hardening and
annealing/tempering metals. Whilst not being by any means an expert - big
subject - I worked testing metals in a lab for a while, and actually had
to measure thickness of the case hardening on mild steel strip: we cut the
strip into randomly selected small sections, then encapsulated them in
perspex cylinders with a nifty hot press (also handy for making souvenir
coin etc key fobs) cut it in sections; polished to mirror finish; etch in
conc HCl or similar, and then inspect under microscope and measure dark
edge. Also had to try and measure hardness across the strips too -
measuring the diagonals of a square produced by diamond with weights
attached. Pain in the neck actually, and hard statistical work in the
days when a calculator was a curiosity only affordable by devoted Sinclair
fans... ah the little red lights... memories...

Anyhow, secret white powder you can all use next time to make a big hole
in a wall and don't want to pay out for a drill you only use once? You
have it by the kilo and it begins with S and ends in r. You got it. I'm
surprised nobody has mentioned the trick for putting water pipes through
walls: probably all spoiled rotten by power tools! Standard piece of iron
water pipe - prob should wear mask as often lead lined: cut a jagged end
of rough teeth on a length long enough to go through wall; blowlamp on end
with said teeth till red hot - or hot as it gets before the gas runs out;
dunk straight into pot of sugar, Lots of candyfloss smells and smoke and
flames, so not to be done near your petrol cans or old newspapers!
Actually any suitably coating carbon source will do, and old engine oil
was also favoured by some, but sugar works fine and I generally have a pot
of it in the garage for odd bits and pieces that want toughening. At a
pinch you can even make your own springs...

I found that a dunk or two in the sugar bowl enabled me to bore through a
cavity brick wall fairly neatly with the hammer and turn method similarly
used with the old rawplug tools. Probably not quite as neat as modern
drills, but such things were way beyond the pockets of mere mortals once
upon a time, before those wonderful Chinese people caught the capitalist
bug.

As for sharpening chisels and plane blades, it is quite hard to hold them
at the 25 or 30 degrees positions by hand (and for drills very
mindboggling, but you can get an eye for the angles in the end), but I
have a very handy little clamp on a roller made by Eclipse, that you clamp
your chisel or plane blade in; make sure the correct length is projecting
for the angle in question, and then you roll it up and down your series of
oil stones until all is razor sharp and satisfactory. Always start any
job with sharpening the chisels and plane blades: satisfying and saves on
lengthy once in a blue moon regrinds.

And while we are on blue. The hardness and temper of steels is of course
ultimately dependent on their composition: some can be so hard it is
difficult to find anything to cut them with once they have been heat
treated (skilled metallurgists can get a good idea of the
composition/hardness by looking at the colour of the sparks as they grind:
not me). When grinding with a grindwheel always have a pot of water handy
and keep dunking. For heftyish things like cold chisels dunk well before
your fingers get hot or you will make the end so brittle it just snaps off
when you hit the other end. With screwdrivers it's even more fussy as
they heat up very quickly and are easily ruined, and will either snap as
soon as you turn them, or twist like cheese (if it was only a cheap case
hardened one). There are tables of temper colours for different purposes
'straw' coloured tending to be harder than 'blue' for example - but again
varying with the metal. Straw just at the tip, for cold chisels, and
grading into blue behind, to give a little bounce rather than snap...

Another v interesting subject...

S


Indeed, and I've learnt a lot - thanks all. The particular chisel in
question was only a DIY shop 'cheapo'. I have sharpened it regularly, but
only ever on a coarse / fine two sided oilstone, so not been overheated on a
wheel. I wouldn't say that I am 'artisan skilled' at blade sharpening, but
we were taught it at school in the woodworking classes many many moons ago,
and I think that I am pretty fair at getting a good edge at about the right
angle. My test for a good edge is to see if it will cut a piece of bent
paper across its whole width. If it does, that seems to me to be a good
enough edge for construction level woodworking. Cabinet making might be a
different story, but this chisel is usually just used for things like lap
joints on soft pine.

From what's been said, it is probably either just my imagination, or my lack
of skill at precision sharpening, that makes it seem like the edge doesn't
last as long as when it was new. I just assumed that being a cheapie, it was
made from a low quality steel, and had just had its edge hardened
originally, and that over time, I had stoned that away. I'll be doing a fair
amount of chopping out with it today, so be interesting to see how it holds
up.

Arfa

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Default Case hardening ...


"Arfa Daily" wrote in message
news:fkdTn.96339$oi7.64378@hurricane...


"Spamlet" wrote in message
...

"Arfa Daily" wrote in message
...
Many years ago, my brother in law, who was a mechanical engineer

/
toolmaker, gave me a bag of 'case hardening powder', which I

still have.
Does anyone know what exactly this stuff is (it's white, and if

the
police got hold of it, I'd probably be locked up whilst they

determined
just what it was ...) and how to use it ? I got to thinking about

it
today, when I was stoning the edge on a chisel ready for use

tomorrow on
a job. It occurred to me that once the original factory edge has

gone
from a wood chisel or plane blade or whatever, and you've

resharpened it,
it never seems to last as long again as it originally did. Is

this
because they harden the edge when it's made ? Is it appropriate,

or even
possible with home DIY facilities, to harden the edge once it's

been
restored ?

Arfa



It's quite amusing reading some of the comments about secret

recipes of
potions and powders for case hardening, and for hardening and
annealing/tempering metals. Whilst not being by any means an

expert - big
subject - I worked testing metals in a lab for a while, and

actually had
to measure thickness of the case hardening on mild steel strip: we

cut the
strip into randomly selected small sections, then encapsulated

them in
perspex cylinders with a nifty hot press (also handy for making

souvenir
coin etc key fobs) cut it in sections; polished to mirror finish;

etch in
conc HCl or similar, and then inspect under microscope and measure

dark
edge. Also had to try and measure hardness across the strips

too -
measuring the diagonals of a square produced by diamond with

weights
attached. Pain in the neck actually, and hard statistical work in

the
days when a calculator was a curiosity only affordable by devoted

Sinclair
fans... ah the little red lights... memories...

Anyhow, secret white powder you can all use next time to make a

big hole
in a wall and don't want to pay out for a drill you only use once?

You
have it by the kilo and it begins with S and ends in r. You got

it. I'm
surprised nobody has mentioned the trick for putting water pipes

through
walls: probably all spoiled rotten by power tools! Standard piece

of iron
water pipe - prob should wear mask as often lead lined: cut a

jagged end
of rough teeth on a length long enough to go through wall;

blowlamp on end
with said teeth till red hot - or hot as it gets before the gas

runs out;
dunk straight into pot of sugar, Lots of candyfloss smells and

smoke and
flames, so not to be done near your petrol cans or old newspapers!
Actually any suitably coating carbon source will do, and old

engine oil
was also favoured by some, but sugar works fine and I generally

have a pot
of it in the garage for odd bits and pieces that want toughening.

At a
pinch you can even make your own springs...

I found that a dunk or two in the sugar bowl enabled me to bore

through a
cavity brick wall fairly neatly with the hammer and turn method

similarly
used with the old rawplug tools. Probably not quite as neat as

modern
drills, but such things were way beyond the pockets of mere

mortals once
upon a time, before those wonderful Chinese people caught the

capitalist
bug.

As for sharpening chisels and plane blades, it is quite hard to

hold them
at the 25 or 30 degrees positions by hand (and for drills very
mindboggling, but you can get an eye for the angles in the end),

but I
have a very handy little clamp on a roller made by Eclipse, that

you clamp
your chisel or plane blade in; make sure the correct length is

projecting
for the angle in question, and then you roll it up and down your

series of
oil stones until all is razor sharp and satisfactory. Always

start any
job with sharpening the chisels and plane blades: satisfying and

saves on
lengthy once in a blue moon regrinds.

And while we are on blue. The hardness and temper of steels is of

course
ultimately dependent on their composition: some can be so hard it

is
difficult to find anything to cut them with once they have been

heat
treated (skilled metallurgists can get a good idea of the
composition/hardness by looking at the colour of the sparks as

they grind:
not me). When grinding with a grindwheel always have a pot of

water handy
and keep dunking. For heftyish things like cold chisels dunk well

before
your fingers get hot or you will make the end so brittle it just

snaps off
when you hit the other end. With screwdrivers it's even more

fussy as
they heat up very quickly and are easily ruined, and will either

snap as
soon as you turn them, or twist like cheese (if it was only a

cheap case
hardened one). There are tables of temper colours for different

purposes
'straw' coloured tending to be harder than 'blue' for example -

but again
varying with the metal. Straw just at the tip, for cold chisels,

and
grading into blue behind, to give a little bounce rather than

snap...

Another v interesting subject...

S


Indeed, and I've learnt a lot - thanks all. The particular chisel in
question was only a DIY shop 'cheapo'. I have sharpened it

regularly, but
only ever on a coarse / fine two sided oilstone, so not been

overheated on a
wheel. I wouldn't say that I am 'artisan skilled' at blade

sharpening, but
we were taught it at school in the woodworking classes many many

moons ago,
and I think that I am pretty fair at getting a good edge at about

the right
angle. My test for a good edge is to see if it will cut a piece of

bent
paper across its whole width. If it does, that seems to me to be a

good
enough edge for construction level woodworking. Cabinet making might

be a
different story, but this chisel is usually just used for things

like lap
joints on soft pine.

From what's been said, it is probably either just my imagination, or

my lack
of skill at precision sharpening, that makes it seem like the edge

doesn't
last as long as when it was new. I just assumed that being a

cheapie, it was
made from a low quality steel, and had just had its edge hardened
originally, and that over time, I had stoned that away. I'll be

doing a fair
amount of chopping out with it today, so be interesting to see how

it holds
up.

Arfa


If it's a real cheap cheapy it's entirely possible it was case
hardened back where it was born in China. There is a shipment of nasty
Chinese hack saw blades lurking in the small shops / boot fairs that
cease cutting after the first few strokes as the case is very very
thin!

AWEM

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Default Case hardening ...


"Andrew Mawson" wrote in message
...

"Arfa Daily" wrote in message
news:fkdTn.96339$oi7.64378@hurricane...


"Spamlet" wrote in message
...

"Arfa Daily" wrote in message
...
Many years ago, my brother in law, who was a mechanical engineer

/
toolmaker, gave me a bag of 'case hardening powder', which I

still have.
Does anyone know what exactly this stuff is (it's white, and if

the
police got hold of it, I'd probably be locked up whilst they

determined
just what it was ...) and how to use it ? I got to thinking about

it
today, when I was stoning the edge on a chisel ready for use

tomorrow on
a job. It occurred to me that once the original factory edge has

gone
from a wood chisel or plane blade or whatever, and you've

resharpened it,
it never seems to last as long again as it originally did. Is

this
because they harden the edge when it's made ? Is it appropriate,

or even
possible with home DIY facilities, to harden the edge once it's

been
restored ?

Arfa


It's quite amusing reading some of the comments about secret

recipes of
potions and powders for case hardening, and for hardening and
annealing/tempering metals. Whilst not being by any means an

expert - big
subject - I worked testing metals in a lab for a while, and

actually had
to measure thickness of the case hardening on mild steel strip: we

cut the
strip into randomly selected small sections, then encapsulated

them in
perspex cylinders with a nifty hot press (also handy for making

souvenir
coin etc key fobs) cut it in sections; polished to mirror finish;

etch in
conc HCl or similar, and then inspect under microscope and measure

dark
edge. Also had to try and measure hardness across the strips

too -
measuring the diagonals of a square produced by diamond with

weights
attached. Pain in the neck actually, and hard statistical work in

the
days when a calculator was a curiosity only affordable by devoted

Sinclair
fans... ah the little red lights... memories...

Anyhow, secret white powder you can all use next time to make a

big hole
in a wall and don't want to pay out for a drill you only use once?

You
have it by the kilo and it begins with S and ends in r. You got

it. I'm
surprised nobody has mentioned the trick for putting water pipes

through
walls: probably all spoiled rotten by power tools! Standard piece

of iron
water pipe - prob should wear mask as often lead lined: cut a

jagged end
of rough teeth on a length long enough to go through wall;

blowlamp on end
with said teeth till red hot - or hot as it gets before the gas

runs out;
dunk straight into pot of sugar, Lots of candyfloss smells and

smoke and
flames, so not to be done near your petrol cans or old newspapers!
Actually any suitably coating carbon source will do, and old

engine oil
was also favoured by some, but sugar works fine and I generally

have a pot
of it in the garage for odd bits and pieces that want toughening.

At a
pinch you can even make your own springs...

I found that a dunk or two in the sugar bowl enabled me to bore

through a
cavity brick wall fairly neatly with the hammer and turn method

similarly
used with the old rawplug tools. Probably not quite as neat as

modern
drills, but such things were way beyond the pockets of mere

mortals once
upon a time, before those wonderful Chinese people caught the

capitalist
bug.

As for sharpening chisels and plane blades, it is quite hard to

hold them
at the 25 or 30 degrees positions by hand (and for drills very
mindboggling, but you can get an eye for the angles in the end),

but I
have a very handy little clamp on a roller made by Eclipse, that

you clamp
your chisel or plane blade in; make sure the correct length is

projecting
for the angle in question, and then you roll it up and down your

series of
oil stones until all is razor sharp and satisfactory. Always

start any
job with sharpening the chisels and plane blades: satisfying and

saves on
lengthy once in a blue moon regrinds.

And while we are on blue. The hardness and temper of steels is of

course
ultimately dependent on their composition: some can be so hard it

is
difficult to find anything to cut them with once they have been

heat
treated (skilled metallurgists can get a good idea of the
composition/hardness by looking at the colour of the sparks as

they grind:
not me). When grinding with a grindwheel always have a pot of

water handy
and keep dunking. For heftyish things like cold chisels dunk well

before
your fingers get hot or you will make the end so brittle it just

snaps off
when you hit the other end. With screwdrivers it's even more

fussy as
they heat up very quickly and are easily ruined, and will either

snap as
soon as you turn them, or twist like cheese (if it was only a

cheap case
hardened one). There are tables of temper colours for different

purposes
'straw' coloured tending to be harder than 'blue' for example -

but again
varying with the metal. Straw just at the tip, for cold chisels,

and
grading into blue behind, to give a little bounce rather than

snap...

Another v interesting subject...

S


Indeed, and I've learnt a lot - thanks all. The particular chisel in
question was only a DIY shop 'cheapo'. I have sharpened it

regularly, but
only ever on a coarse / fine two sided oilstone, so not been

overheated on a
wheel. I wouldn't say that I am 'artisan skilled' at blade

sharpening, but
we were taught it at school in the woodworking classes many many

moons ago,
and I think that I am pretty fair at getting a good edge at about

the right
angle. My test for a good edge is to see if it will cut a piece of

bent
paper across its whole width. If it does, that seems to me to be a

good
enough edge for construction level woodworking. Cabinet making might

be a
different story, but this chisel is usually just used for things

like lap
joints on soft pine.

From what's been said, it is probably either just my imagination, or

my lack
of skill at precision sharpening, that makes it seem like the edge

doesn't
last as long as when it was new. I just assumed that being a

cheapie, it was
made from a low quality steel, and had just had its edge hardened
originally, and that over time, I had stoned that away. I'll be

doing a fair
amount of chopping out with it today, so be interesting to see how

it holds
up.

Arfa


If it's a real cheap cheapy it's entirely possible it was case
hardened back where it was born in China. There is a shipment of nasty
Chinese hack saw blades lurking in the small shops / boot fairs that
cease cutting after the first few strokes as the case is very very
thin!

AWEM


And quite a few that are 'case hardened' all the way through and snap at the
slightest touch and have teeth pinging off in all directions...

I'd put in a plug for abrafile 'blades' here though - marvellous things.

:-)
S


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"Arfa Daily" wrote in message
news:fkdTn.96339$oi7.64378@hurricane...


"Spamlet" wrote in message
...

"Arfa Daily" wrote in message
...
Many years ago, my brother in law, who was a mechanical engineer /
toolmaker, gave me a bag of 'case hardening powder', which I still have.
Does anyone know what exactly this stuff is (it's white, and if the
police got hold of it, I'd probably be locked up whilst they determined
just what it was ...) and how to use it ? I got to thinking about it
today, when I was stoning the edge on a chisel ready for use tomorrow on
a job. It occurred to me that once the original factory edge has gone
from a wood chisel or plane blade or whatever, and you've resharpened
it, it never seems to last as long again as it originally did. Is this
because they harden the edge when it's made ? Is it appropriate, or even
possible with home DIY facilities, to harden the edge once it's been
restored ?

Arfa



It's quite amusing reading some of the comments about secret recipes of
potions and powders for case hardening, and for hardening and
annealing/tempering metals. Whilst not being by any means an expert -
big subject - I worked testing metals in a lab for a while, and actually
had to measure thickness of the case hardening on mild steel strip: we
cut the strip into randomly selected small sections, then encapsulated
them in perspex cylinders with a nifty hot press (also handy for making
souvenir coin etc key fobs) cut it in sections; polished to mirror
finish; etch in conc HCl or similar, and then inspect under microscope
and measure dark edge. Also had to try and measure hardness across the
strips too - measuring the diagonals of a square produced by diamond with
weights attached. Pain in the neck actually, and hard statistical work
in the days when a calculator was a curiosity only affordable by devoted
Sinclair fans... ah the little red lights... memories...

Anyhow, secret white powder you can all use next time to make a big hole
in a wall and don't want to pay out for a drill you only use once? You
have it by the kilo and it begins with S and ends in r. You got it. I'm
surprised nobody has mentioned the trick for putting water pipes through
walls: probably all spoiled rotten by power tools! Standard piece of
iron water pipe - prob should wear mask as often lead lined: cut a jagged
end of rough teeth on a length long enough to go through wall; blowlamp
on end with said teeth till red hot - or hot as it gets before the gas
runs out; dunk straight into pot of sugar, Lots of candyfloss smells and
smoke and flames, so not to be done near your petrol cans or old
newspapers! Actually any suitably coating carbon source will do, and old
engine oil was also favoured by some, but sugar works fine and I
generally have a pot of it in the garage for odd bits and pieces that
want toughening. At a pinch you can even make your own springs...

I found that a dunk or two in the sugar bowl enabled me to bore through a
cavity brick wall fairly neatly with the hammer and turn method similarly
used with the old rawplug tools. Probably not quite as neat as modern
drills, but such things were way beyond the pockets of mere mortals once
upon a time, before those wonderful Chinese people caught the capitalist
bug.

As for sharpening chisels and plane blades, it is quite hard to hold them
at the 25 or 30 degrees positions by hand (and for drills very
mindboggling, but you can get an eye for the angles in the end), but I
have a very handy little clamp on a roller made by Eclipse, that you
clamp your chisel or plane blade in; make sure the correct length is
projecting for the angle in question, and then you roll it up and down
your series of oil stones until all is razor sharp and satisfactory.
Always start any job with sharpening the chisels and plane blades:
satisfying and saves on lengthy once in a blue moon regrinds.

And while we are on blue. The hardness and temper of steels is of course
ultimately dependent on their composition: some can be so hard it is
difficult to find anything to cut them with once they have been heat
treated (skilled metallurgists can get a good idea of the
composition/hardness by looking at the colour of the sparks as they
grind: not me). When grinding with a grindwheel always have a pot of
water handy and keep dunking. For heftyish things like cold chisels dunk
well before your fingers get hot or you will make the end so brittle it
just snaps off when you hit the other end. With screwdrivers it's even
more fussy as they heat up very quickly and are easily ruined, and will
either snap as soon as you turn them, or twist like cheese (if it was
only a cheap case hardened one). There are tables of temper colours for
different purposes 'straw' coloured tending to be harder than 'blue' for
example - but again varying with the metal. Straw just at the tip, for
cold chisels, and grading into blue behind, to give a little bounce
rather than snap...

Another v interesting subject...

S


Indeed, and I've learnt a lot - thanks all. The particular chisel in
question was only a DIY shop 'cheapo'. I have sharpened it regularly, but
only ever on a coarse / fine two sided oilstone, so not been overheated on
a wheel. I wouldn't say that I am 'artisan skilled' at blade sharpening,
but we were taught it at school in the woodworking classes many many moons
ago, and I think that I am pretty fair at getting a good edge at about the
right angle. My test for a good edge is to see if it will cut a piece of
bent paper across its whole width. If it does, that seems to me to be a
good enough edge for construction level woodworking. Cabinet making might
be a different story, but this chisel is usually just used for things like
lap joints on soft pine.

From what's been said, it is probably either just my imagination, or my
lack of skill at precision sharpening, that makes it seem like the edge
doesn't last as long as when it was new. I just assumed that being a
cheapie, it was made from a low quality steel, and had just had its edge
hardened originally, and that over time, I had stoned that away. I'll be
doing a fair amount of chopping out with it today, so be interesting to
see how it holds up.

Arfa


I thought I was quite good at manually gauging blade angles until I got the
sharpening guide. If they are still available they are well worth having.
One thing they can help prevent is the end of the blade getting out of
square, which is a pain in the neck in a plane blade, when you soon run out
of adjustment on the side to side lever. You will almost always get a curve
rather than a level angle with 'bare hand' honing too. Getting it back
level and square again can be a long job, but if you always sharpen at the
same set angle the problem is minimised (yes you can still press harder on
one side than the other even with a honing guide). And, it is worth having a
jig for drills too if you do a lot of drilling.

S




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Default Case hardening ...

On 19/06/2010 22:40, Andy Dingley wrote:
On 19 June, 18:25, wrote:

Moving on to the case hardening powder you have, this will consist of
animal bones.


No bones in it - hoof and horn instead.

Bone is a poor carbon donor and a good phosphorus donor, which is
generally a bad thing in steels.


Thanks for the reminder, it's been a long time since I learned about it.

Dave
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snip


I thought I was quite good at manually gauging blade angles until I got
the sharpening guide. If they are still available they are well worth
having. One thing they can help prevent is the end of the blade getting
out of square, which is a pain in the neck in a plane blade, when you soon
run out of adjustment on the side to side lever. You will almost always
get a curve rather than a level angle with 'bare hand' honing too.
Getting it back level and square again can be a long job, but if you
always sharpen at the same set angle the problem is minimised (yes you can
still press harder on one side than the other even with a honing guide).
And, it is worth having a jig for drills too if you do a lot of drilling.

S


OK, here's the update. Chisel has performed absolutely fine all day, and
edge still seems ok, despite there being a knot at just about every bloody
place that I had to chop out, Why is knot wood in otherwise sos pine, so
incredibly hard ?

Arfa

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Default Case hardening ...

On 19 June, 17:47, "Arfa Daily" wrote:
Many years ago, my brother in law, who was a mechanical engineer /
toolmaker, gave me a bag of 'case hardening powder', which I still have.
Does anyone know what exactly this stuff is (it's white, and if the police
got hold of it, I'd probably be locked up whilst they determined just what
it was ...) and how to use it ? I got to thinking about it today, when I was
stoning the edge on a chisel ready for use tomorrow on a job. It occurred to
me that once the original factory edge has gone from a wood chisel or plane
blade or whatever, and you've resharpened it, it never seems to last as long
again as it originally did. Is this because they harden the edge when it's
made ? Is it appropriate, or even possible with home DIY facilities, to
harden the edge once it's been restored ?

Arfa


The case hardening stuff is usually black & flaky and made
traditionally from burnt leather. The only things you're likely to
come across that's case hardened is hammer heads and some of these
fancy new wood screws.
Case hardening is only a few thou's thick.
You can restore your chisel if you have oxy-acetylene and know what
you're about. When sharpening your chisel on a bench grinder, don't
let it over heat, and keep dipping it in water every few seconds.
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Default Case hardening ...

We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember "Spamlet"
saying something like:


unnecessary verbiage snipped

And quite a few that are 'case hardened' all the way through and snap at the
slightest touch and have teeth pinging off in all directions...


I've had a few of those. Never again trusted market/fair/bootsale crap,
unless it's obviously genuine stuff.
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"Arfa Daily" wrote in message
news:vEqTn.40228$OF3.3318@hurricane...

snip


I thought I was quite good at manually gauging blade angles until I got
the sharpening guide. If they are still available they are well worth
having. One thing they can help prevent is the end of the blade getting
out of square, which is a pain in the neck in a plane blade, when you
soon run out of adjustment on the side to side lever. You will almost
always get a curve rather than a level angle with 'bare hand' honing too.
Getting it back level and square again can be a long job, but if you
always sharpen at the same set angle the problem is minimised (yes you
can still press harder on one side than the other even with a honing
guide). And, it is worth having a jig for drills too if you do a lot of
drilling.

S


OK, here's the update. Chisel has performed absolutely fine all day, and
edge still seems ok, despite there being a knot at just about every bloody
place that I had to chop out, Why is knot wood in otherwise sos pine, so
incredibly hard ?

Arfa


That is a very good question. Thinking about it: the new trunk rings of the
tree have to work their way out around the side branches; sort of making a
sleeve around them and then needing to seal it all up with resin as they go.
Interesting thought.

S




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On Jun 20, 4:41*pm, "Arfa Daily" wrote:
Why is knot wood in otherwise sos pine, so incredibly hard ?


Kiln dried, and over-cooked while they were doing it.
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"John" wrote in message
news:Qd7Tn.5333$cG5.5144@hurricane...

Be very careful - it could be Cyanide


I was going to say that. When I did my engineering apprenticeship in the
late 70's, ( proper 5 year apprenticeship not like these 4 week NVQ's or
whatever they do today ), we used a Cyanide powder solution to case harden
the scrapers etc. we made.

John


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"John" wrote in message
...

"John" wrote in message
news:Qd7Tn.5333$cG5.5144@hurricane...

Be very careful - it could be Cyanide


I was going to say that. When I did my engineering apprenticeship in the
late 70's, ( proper 5 year apprenticeship not like these 4 week NVQ's or
whatever they do today ), we used a Cyanide powder solution to case harden
the scrapers etc. we made.

John


It's gone back in the drawer for another 20 years .... !! :-)

Arfa

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