Ravenson on fri 20 apr 01
Ok Bill I am not an expert but have done some knife makeing as a hoby in =
collage maybe I can ansewer some of you questions.
Hi Clive:
I really know very little about the physical properties of metals. I =3D
observed that the steel that files are made of, when heated orange-hot, =
=3D
becomes very hard and brittle (ie will break if you drop the tool).=20
at this point the metal is fully hardened, most high carbon steel and =
Stainless steel. Will break or chip if droped on a hard surface when =
it is fully harded, some types (higher carbon) like W2 (older files) =
have as much as .060 -1.40 carbon. This meens that in the fully =
hardend state they can break very easly.=20
=20
I assumed that this hardness is a desirable feature in that the blade =
=3D
should hold its edge longer than a softer steel. Maybe this assumption =
=3D
is incorrect.=20
Nope your right this is while files are made of this steel when tempered =
right it is very hard and holds its edge well. Also since files are =
often used to cut(file) metal they have to be hard.
The trimming tools I have made from this material do seem =3D
to hold an edge for quite a while, but I have not tried to compare them =
=3D
with other tools. Do you think that spring steel, properly tempered as =
=3D
you described, would hold an edge equally well? or better? Would the =
=3D
spring steel be easier to sharpen?
Humm ok first spring steel can be one of several different types of =
steel, but in most cases properly tempered spring steel is going to be =
easer to sharpen because it is to be softer. As it is softer it is =
not going to hold an edge as long it a trade off. As steel gets harder =
it is les flexable but wears better, but it is also more britle. =
Softer steel more flex , less britle. Am I makeing scince.
Are metal files brittle because they were heated to a higher temperature =
=3D
before being quenched ... or is the alloy different from what you call =
=3D
spring steel? ... or both?
Both
If you heat file steel to a dull red before =3D
quenching it, will it be springy and less brittle?
Ok now we have to talk abouty how to temper. First heat your metal up =
till a magnite will not stick to it, or if you know what type of steel =
it is heat it up to the tempering range. For most carbon steel this is =
in the red hot range. An old blacksmiths trick is if a magnet does not =
stick to it. It is hot enough. Then quench the metal in the proper =
tempering medim, for most old files (W2 steel) oil will be fine. Let =
the metal cool in the oil. It will be fully harded at this point, and =
if droped may shatter.
Now we temper the metal. The pice is cleaned to a bright shiny surface, =
sandpaper or carefully work with a grinder ok, it does not need to be a =
miror finsh. Now slooowly heart the metal up again as you do watch =
the shinly part. as the metal gets hot it will change colors. The =
colors go from pale yellow to blue gray, most knives are in the bright =
yellow range but spring steel is in the blue range. =20
I guess the short ansewer to if you heat to dull red before quenching =
is. On some metals yes on most no the only way to tell is to try it. =
If you want to do it right the steps above will give you a idea of how, =
but I would find a blacksmith in the area and ask him/or her to help =
you.
Now haveing said all that let me say this. If it works do it. I =
bleive Mel also posted a shorter way on how to do this.
Jeff James
=20
Joseph Herbert on sun 22 apr 01
Jeff James writes a good treatment on heat treating metal tools. However,
there is one detail that deviled me for a long time, until the dawn broke.
In discussions of heat treating metals, especially tempering tools, the
desired color of the metal at various stages is stated. I was long confused
because I didn't understand there are two kinds of colors in the discussion.
When speaking of heating steels to achieve the hardening induced by rapid
cooling (quenching) the colors are those we see in the peep hole of the
kiln. The colors that indicate the temperature of the object in the black
body radiation kind of sense.
The other kind of color that Mr. James mentions at the end of his piece are
OXIDATION colors on the surface of the piece being heated. The pale straw,
blue, and other colors described are related to the temperature of the
material but are from an entirely different phenomenon as the earlier
prequenching colors. The polishing of the surface greatly improves the
display of these colors and allows more accurate gauging of the result of
the 'Tempering" process. All of these colors occur far below the "red heat"
of the other kind of colors.
Anyway, I have found this difference rarely (never?) stated in these
discussions and confess my long ignorance here in hopes that others are
saved the mystification.
Joseph Herbert
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