We are assuming
you are using W1 water hardening square stock drill rod, W1 tool steel.
Many suppliers will sell W1 tool steel. It is often called drill rod (In
England 'silver steel'). It should be square for less work in tool making,
but round drill rod can be filed or forged to square. You should not use
key stock, which some hardware suppliers will try and sell to you: it
cannot be hardened as described below.
- Cut a tool steel to length
Approximately from the tip of your index finger to two/thirds the
distance from where your finger joins the hand and where the thumb
- If necessary, anneal the steel.
Heat to bright orange-red (until the 'shadows' disappear) and heap
a refractive material (pumice, graphite, broken firebrick, ashes,
kitty liter, etc.) on it, leaving it alone until cool. W1 drill comes
already dead soft and does not need to be annealed.
- Forge or file square. (if using round stock)
Forge hot and true the length of the rod until mostly square. (or
use the square stock-a favorite source of mine is MSCdirect.com.
Forging retains metal = a bigger tool blank, filing reduces it.
For a stamp, or matting tool it works (if done correctly) to hammer
the blank cold just on two sides so that you have a flattened oval.
This is sufficient for a stamp, provided there are actual flat sides.
The reason for square stock is that it gives excellent control.
- Taper back end, streamline the tool, prepare
Be aware of the trueness of your filing. It should remain square in
section (the blank) as you work.
The taper from face to back should be about (just under) two-thirds
the length of the tool. The back taper begins gently at that point.
Depending on the tool, the point where the taper changes should be
the starting square section of the stock. i.e. start with 3/8"
and the taper change point is 3/8" square.
The reason for the taper is better control. The tapered tool should
be balanced and feel slightly lighter than it looks.
The front is hot forged gently to a small rectangle to prepare for
upsetting. The sharp edges are then beveled a bit to prevent metal
cracking and splitting when upsetting.
A blank of W1 water hardening tool steel can also be step rolled in
the wire rolling mill to taper it and prepare its shape. This saves
lot of work and allows a shorter piece of steel to be used - as it
is lengthened by the step rolling. When step rolling steel, remember
to test it by hitting it with a rough hammer before you start. If
it squishes then you can put it in the mill. If nothing happens then
do not use it in the mill as it can damage it.
- Upset face and fold over and under.
Place the tool in a vise, vertically, so that about 1/2" to an
inch protrudes from the vise. Thinner tools protrude less.
Heat and when red-orange tap with a flat or slightly crowned hammer
on the face of the tool. The blows must be exactly perpendicular to
the face of the tool and in the same line as the tool is at first.
This upsets the stock, thickening it.
Keep some water nearby to cool the hammer in occasionally (a quick
dip) as otherwise it may lose it's temper.
When upset sufficiently begin to bring the blows in from a very slight
angle, circling the face as you do so, increasing the angle slowly.
This mushrooms it, almost like rivetting. By increasing the angle
of the blows to the point that they are almost coming from underneath
one can fold the steel under so that it isn't sharp to the touch and
becomes a nice rounded surface.
Finish off with light taps and correct any bending of the shaft that
may have occurred. Sight for symmetry.
- Hot file the face.
Use an old, preferably crummy file.
While the work is red-hot file in long slow strokes the length of
the tool face, following the curve as you do so. This enables you
to correct any symmetrical problems, smooth (almost burnish) the face,
and go straight to emery.
On large work the file may need cooling.
- Finish the tapering of the body of the
It is here that the final balancing occurs.
The shaft behind the head is usually filed down somewhat at this point,
curving smoothly into the head just behind it.
- Emery with course, medium and fine papers.
(cloth works better)
The body may be emeryed now, but it isn't really necessary.
While the body actually needs to be fairly rough for better gripping,
the face should be a mirror finish to allow for easier movement on
the work and to impart a corresponding finish to the work.
A method of emerying is to tear or cut long (6 inch) strips about
1/2 inch wide and by gripping both ends pull it back and forth across
the face (rather like towelling your back dry). Do this in the two
main axes that the face has, as this maintains symmetry.
Another method is to tear or cut a small square of emery cloth (between
1 and 2 inches square) and place it in the palm of your hand. Place
your palm and emery on the tool face and rub back and forth on the
two main axes until the worst is off, then rotate your hand slightly,
occasionally changing the angle which you are rubbing at. This constantly
changes the emery at any one point on the tool, randomly distributing
the pressure and quality of abrasion, making for an evenly emeryed
tool. It works best for a rounded tool like a planisher or flattened
tapping tool, but when combined with an occasional linear movement
along the two main axes it works very well.
Moving the emery in one direction for a second or two enables one
to check the evenness of one's emerying.
For tools with flat faces, placing the emery on a flat surface and
moving the tool over the emery is sometimes more effective.
The principle of random emerying is important in even abrasion.
Use at least three grades of emery or cloth.
- Polish the face.
Tripoli first, wash and scrub in soap and ammonia and then go to rouge.
It is possible to bring the face to a satisfactory degree of polish
with fine emery and crocus cloth.
A faster alternative is to use a steel "cutting and coloring"
compound such as Saphralite. A steel polishing compound like Fabulustre®
is my current favorite method. These compounds are usually white and
both abrade and polish at the same time.
Use the above methods on a machine buff, or if you have lots of time
on your hands use a piece of leather with diamond powder or tin oxide
on it. Green or yellow rouge works too.
- Prepare for hardening (quenching)
At this point you should have a tool that looks finished, has a polished
face and bared, clean steel sides. If it doesn't then at least the
length of one side should be bared with a file. This is to allow the
later observation of the tempering colors.
Build a "kiln" or muffle with fire-bricks as shown. For
the floor use a brick that has obviously been used for it before.
i.e. with melted flux on it.
It saves time to prevent oxidation on the face and bared side of
the tool, rather than cleaning the scale formed by heating after quenching.
Therefore we prevent the oxidation on those surfaces. SOAP!
We can prevent oxygen from reaching the surface (and causing scale)
by covering it various materials. Best of all is ordinary bar soap,
just slide the warmed tool on the soap until it melts and coats it.
I recommend this over other options. In the past I have used a stoneware
or porcelain slip. Mix it to the consistency of cream and dip the
tool face (and side if possible) in. Dry with a light flame and repeat
the dip at least once. I found porcelain to work better. The more
finely ground the better too.
In some cases a good coating of borax flux (Handy Flux) is useful
- but nothing is as good as bar soap. The borax is sticky and doesn't
crack off as the clay slips may do. It absorbs oxygen as well as shielding
the surface from the air. In a water quench the shock is enough to
shatter it off but in oil it remains, requiring a quick brush with
a file. Another disadvantage is that it makes the brick messy. So
use one already used for the purpose. The clay slips shatter off nicely
in either water or oil.
One can lessen the amount of oxygen reaching the surface by using
a reducing flame on the torch. That is a flame with more gas than
air in it, usually characterized by a large light blue secondary cone
on the flame. An oxyacetylene torch may be adjusted to a yellowish
flame, more gas than air.
- Quench in water or oil.
The purpose of quenching the tool is to harden the crystal structure.
After this hardening it is then softened, which process is known as
tempering. When it is quenched into a cooling liquid it becomes as
hard as the steel which it is made of is capable of becoming. W1 is
intended to quench in water most of the time.
There are three main liquids one may quench in: water, brine and
oil. They are listed in the order in which they transmit heat (or
the rate at which they cool the steel), water fastest, brine next
and oil the slowest. For our tools they are the only cooling media
we need to be concerned with.
The cooling rate is important because the slower the rate the softer
the inside of the piece of steel. In all three liquids the outside
of the steel is the same hardness but the inside varies according
to the cooling rate of the quench. In steel this means that a tool
with varying hardnesses (soft inside, hard out) is tougher than one
with less variation. The cooling rate also varies with the size of
the steel stock, so that for the average relatively thin chasing tool
oil is the best quench. If quenched too fast steel will crack, sometimes
a good test of a correct quench. For thicker tools where the inside
would get too soft it is a good idea to use a faster quench. Old motor
oil is good and readily available in bulk.
It is certainly possible to quench W1 chasing tools in water without
apparent ill effect.
The tool is brought to an even orange-red heat with a big (#7-8 acetylene/air
tips) torch, until "the shadows disappear", that is when
all the darker patches fade into an even red heat. If you need to
you can have a magnet on a chain and hold it onto the glowing steel.
If the magnet does not stick then it is the right temperature to quench
for maximum hardening. It is then taken with tongs and plunged into
the quench. If possible it should be quenched on the ascending heat,
while the tool is still gathering heat. It should be plunged in as
vertically as possible to avoid warping, and perhaps moved from side
to side, (if you can do it and still remain vertical, I have problems
and usually forget about it). This prevents unevenly distributed cooling.
The water can also be swirled vigorously beforehand so that no air
bubbles form on the steel to insulate it when hardening. After the
"vibration" stops it may be removed.
It is suggested that one heat the tool until a drop of water will
bubble on it. This is called "taking the snap out" and relieves
stresses in the steel, which may be quite considerable. In the old
days engravers would bake their tools in a loaf of bread (350oF) for
the same reason.
- Bare side if necessary.
It is necessary to sand the surface of the steel so that it can oxidize
properly to show us the tempering colors. Steel oxide scale is very
hard indeed and if clogged in a file may do damage to another piece
of metal. The same goes for using the steel compound on a buff to
remove the scale. Do so if it is unlikely to damage something in the
future. Emery works well.
Be very careful with the tool. Although it is very hard, it is extremely
brittle, like glass, and just tapping it against a table might snap
it in two.
- Tempering the tool.
We already quenched the whole tool all at once. This hardened the
Tempering is actually softening the tool to a certain desired point,
having properties peculiar to that point. As we heat the tool the
hard crystal structure changes. Although by heating it one sacrifices
some hardness one gains toughness. (More "whip, more resiliency,
We have one side and the face bare.
If we heat the tool the softer states correspond to higher temperatures.
They also correspond to a series of layers of oxidation on the surface
of the clean steel. We see these layers of oxidation as different
colors. Therefore we are able to tell what degree of softness has
been attained by what color is present on the surface of the steel.
(These oxidation colors happen also on mild steel and unhardened steel;
for us they are useful because the steel has been hardened).
The order in which the colors appear, from cold to hot is:
|Beginning of color
|Brown with purple spots
Tools intended for different purposes are tempered to different colors.
Chasing tool faces are tempered to pale yellow or light straw while
springs are tempered to purple. The difference between a piece of
spring and a cutting tool or chasing tool are fairly obvious. An idea
of the suggested uses for different colors is useful.
Cutting tools for lathe,
Milling cutters, drills, reamers.
Taps and dies.
Centre punches, cold chisels.
|Purple verging into blue
For our tool we will temper parts of it to different colors, a nice
theoretically constructed tool which will probably last forever but
is perhaps too finely made. It doesn't take much longer than other
tempering methods however, and is a better "feeling" tool.
The face will be light straw, the neck purple back to the main stem
which is brown to dark straw and the back end purple, the very back
perhaps dark blue.
The face is straw yellow for durability, the neck purple for resiliency
and so on.
Holding the tool with tongs heat gently in soft sweeping motions from
the body towards the face. Flutter the flame, so that the heat takes
a while to build up and gives you some time to control what happens.
The colors will appear in the order of their corresponding temperatures.
When the colors are at or almost at the correct point the tool must
be immediately cooled in water. It takes a little practice to learn
when to begin moving your hand for the quench, but it isn't hard to
do. It is possible to retard the temperature in one part by dipping
it in water while one heats another section of the tool.
You now have a tool which has on it's surface a visual record of what
hardnesses are present where in the tool. If you softened parts too
much, repeat steps 9-13.
It is essential that there be no hard spots in a tool, as people have
been blinded before when an un-tempered hard spot shattered as a tool
was struck. Make sure that all the back and middle of the tool show
tempering colors, at least to purple or blue to avoid this very real
- Polish the face.
This is mainly for looks. Some chasers never go to a buff again but
use crocus cloth or a piece of leather mounted on wood with ruby or
diamond powder on it, with a little oil. They use this every now and
then while they are using the tool, which keeps it mirror-bright and
prevents crud from making marks on the metal they are chasing.
- Grind back angle.
This may have been done before the tool was hardened with a file or
a grinding wheel, but it makes a nice finishing process.
The angle is a truncated cone ground on the back end of the tool in
order to give some room for mushrooming metal (which may fly off and
damage one's eyes) caused by hammering. It also provides a smaller
area for the hammer to hit, hopefully centered over the main axis
of the tool, making for more effective use of the blow.
When turning a grinding wheel on always stand aside from the front
of the wheel, as a cracked wheel may fly apart when starting and fill
you with little bits of grindstone. You should stand aside at least
until the wheel reaches full speed and preferably a little after that.
You should use the front of the wheel only and if grinding a flat
plane, draw the steel (steel only) across the face of the wheel, cooling
it occasionally in water to prevent temper loss or burning of the
steel. For our taper grinding, hold the steel rod between the thumb
and forefinger of one hand braced on the tool rest, and turn the tool
at the other end with the other hand, grinding a taper onto the tool.
- Test back angle hardness.
Draw a file across the back or hit it with an already scarred hammer
to see if the metal is soft enough to give so as not to harm the chasing
hammer. It should flatten ever so slightly when hit. If it's too hard
the file skids or the hammer is dented. Temper further if necessary.
- Hold the tool correctly when using it.
This method of holding the tool is a Northern European one and is
perhaps the best controlled method of using a chasing tool. Place
your left (for right handed people) third finger on the table. Place
your middle finger on top of it and raise your hand in the air so
that the knuckle of your index finger is about in a vertical line
with the knuckle of your middle finger and the two nails of the middle
and third fingers, one over the other. The pinky sticks out and has
no use except that old chasers would hold extra tools in it. The thumb
holds the tool against the other fingers. The position is somewhat
painful at first but the control gained is worth one or two days of
stiff fingers. The reason for the increased control is that the middle
finger acts as a ball-joint, swiveling easily to the required position.
The chasing tool is always stroked towards you, several passes over
the same spot being preferable to one or two heavily hammered ones.
Light tapping blows are the best. It helps not to grip the hammer
but to let it flop in the hand, so that the weight of the hammer head
falling is what actually hits the tool and not a blow of the hand
or the wrist.
- Some further points.
When forging out on the anvil, keep the end of the tool being forged
at the edge of the anvil thus avoiding damaging either hammer or anvil.
See 4. d.
Acetylene torch tips #6 and #8 are better for a broad flame than #7,
which is a finer jet.
See TEMPERING for other methods of dealing with hardening tool steel.
A proper understanding of the process enables one to be flexible enough
to take intelligent advantage of a tool making situation.
The better a tool feels in the hand (run your fingers up and down
it while holding it in your hand) the easier it will be to work with,
leading to a change for better work. A well made tool is beautiful
to look at also.
Use goggles on the grinding wheel and think always before you do something
for the first, second or more times.
- Suggested reading.
Modern Blacksmith and The
Making of Tools by Weygers.
Creative Iron Work by Meilach.
Machine Tool Operation by Burghardt.
The New Edge of the Anvil, by Andrews