Forge a Corkscrew
One of the good things about
getting together with other
blacksmiths is that there's
always something new to learn
from them.
At the 2010 Spokane County
Fair, John Huffstutter showed
me how easy it is to make a
corkscrew's coil using only one
tool -- a hammer. So, with a
bow to John and to his
teachers, I'll pass the technique
on to anyone who visits this
web site.
The first step is to form the leaf. The leaf is made using a technique that probably goes
back two thousand years, but was taught to me by Tim Middaugh.
When you're making leaves, it is important to make them in as few heats, and with as few
hammer blows, as possible. The more hammer blows and the more heats you use, the
more likely the leaf will break off where it joins the stem.
Start out with a rod about two feet long so you can handle it without tongs. You will cut it
off later. Form a four-sided pyramid on the end of the rod. A short pyramid is better than
a longer pyramid. One of the best ways to do this is on the rounded edge of your anvil
face. Heat the rod to yellow-hot, and hold it at the rounded edge, tilted up at the angle
you want for your pyramid. Don't hang the rod's end past the edge. Hold it like so:
Notice that the arrow I've drawn for the
direction of the hammer blow is not lined
up with the hammer. "Stroking" the
hammer (so the impact is at an angle to the
hammer's face) pulls metal to form the
pyramid's point faster.
Next, form the stem of the leaf. You can
still use the rounded edge of the anvil face,
but select a place where the radius of the
edge is small, less than 1/8". Place the rod
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so it overhangs the far edge by about 1.25" and is angled slightly downward. Using halfface blows, form a notch about 2/3 through the rod.
Rotate the rod 90 degrees and
repeat, forming a notch a little
more than 1/2 through the rod..
Go back and forth between the
two notches (only on two sides!)
until the stem you're forming has
a square cross section about 1/2
to 1/3 the diameter of the original
rod.
On a larger-radius portion of
your anvil's edge, draw out the
stem until it is about 4.5 inches
long.
Do NOT hammer your piece as shown in the drawing below. If you do, it will flex the
stem where it joins the leaf, will form cracks, and the leaf will eventually break off.
On the worked end of your two-foot rod, you should end up with 4.5 inches of about
3/16" square rod, terminating in a cylindrical chunk with a pyramid on the end. The stem
will be offset on the end of the cylindrical section, flush with the side of the pyramid at
one point.
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Now round the stem. Knock in the corners of the square cross section to make an
octagonal cross section, then knock in the corners of the octagon and it will be very
nearly round. Make sure you always hang the thicker part that has a pyramidal point off
the edge of the anvil, so you don't flex the material where the stem starts.
Note that there is only one way you can lay your workpiece on the anvil face (as shown
in the drawing above), so that there is no gap between the face and the workpiece. This is
because you only notched the rod from two directions 90 degrees apart. Heat it to
yellow-orange, lay it flat on the anvil face in that one way, and hit it hard with a heavy (2
or 3 lb) hammer, straight down against the anvil face.. Flatten it to about 1/8" thick.
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Re-heat. Switch to a smaller hammer for greater control and use stroking blows to pull
metal toward the edges of the leaf, leaving the center line of the leaf thicker than the
edges. I like to use the anvil horn for this operation.
Heat to orange and vein the leaf, starting with a straight fuller for the center vein and
then using curved fullers for the side veins. Here are photos of my three veining fullers.
After it is first veined, the leaf is flat and
lifeless. Give it some life by bending the
leaf's point over sideways, and putting
some ripple into the leaf.
My favorite tool for this doesn't have a name. Maybe it could be called a "squiggle
stake". It's made from 1/2" rod bent into a distorted "S", and welded to a 1"x1"x 2.5" bar.
The bar fits into the hardie hole. I also like to use my "leafing hammer", which is made
from a railroad Unit Clip.
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Now you can start drawing out the part that will become the corkscrew. You need to
make what amounts to a wire, about 3/32" in diameter and about 6" long. That is 1/4 the
original diameter of your rod, so to make an 6" wire you only need 3/8" of your 3/8" rod
(it will draw out to 4x4=16 times its original length). I never believe my calculations,
always start with too much metal, and end up cutting off the excess.
Cut off your 3/8" bar about one inch beyond the end of the stem. For drawing out the
wire, just put the part you're drawing out into your forge. Keep the leaf and stem cool
and avoid flexing them. Hold the leaf and stem in flat tongs or V-bit bolt tongs. It's okay
to dip the leaf and stem into water to keep them cool.
Gradually draw out the rod to make a
wire. You should keep the cross-section
rectangular, with the wide side of the
rectangle never more than about 1.5 times
the width of the narrow side. So, you can
draw out to a thickness of about 5/16",
then rotate 90 degrees and draw down to
about 1/8", then rotate 90 degrees and
draw down to about 3/32", then rotate 90
degrees and make it square. You can start
drawing out on the horn, moving out on
the horn as the cross section of the wire
gets smaller, or using the radiused edge
of your anvil face. Make sure the wire is
uniform along its full length while it is
still square in cross section, then make it
round in cross section. Straighten it
carefully.
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The screw part of a good corkscrew should be smooth. Holding the straight wire end of
your workpiece flat on a chunk of smooth wood, use a sandpaper-wrapped wood block to
make the wire as smooth as you can.
Now make the loop that will serve as a
handle. You can do this with two pairs of
tongs, or clamp the base of the stem in your
vise and use one pair of tongs to do the
bending. At this stage, the plane of the leaf
should be in the plane of the loop. You will
turn the leaf perpendicular to the loop later.
Most corkscrews are right-handed. A lefthanded corkscrew is almost never going to
be used, so make sure your coil goes in the
right direction. Start making the screw by
cutting the wire to a length of 6". Heat the
wire and bend it 90 degrees. For this you
can use a vise.
Next, heat the wire and curl it into a loose
coil. Heat the wire and start tapping the
coil tighter using a light hammer and the
face of your anvil. Your hammer blows
should be light, stroking blows, as you roll
the coil to the left, on the near side of your
anvil face. Keep the coils tight together so
they support each other. The coil will
automatically get more even as it gets
tighter and gains turns. If the coil gets
skewed, hang it over the far side of your
anvil and tap it lightly to straighten it.
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Keep heating, tapping, and rolling the coil until its outside diameter is a bit less than 3/8".
It will have about 5 turns. Make it uniformly round and non-skewed. When the coil looks
like the photo below, heat it up to orange, grip it with two pairs of tongs, and stretch the
coil out.
It is helpful to have a pair of spreading
tongs and some fine-point scrolling
tongs or needle nose pliers to fine-tune
the coil spacing. If you don't have
spreading tongs, a chisel or
screwdriver can serve the purpose.
Use a 1/4" rod to check the coil
spacing, and squeeze or spread to
make the spacing uniform.
Heat and twist the leaf stem so the
plane of the leaf faces the same
direction as the screw. When the
corkscrew is used to pull a cork, the
user's fingers will rest against the leaf's
veined face and it should be
comfortable to the hand.
After the whole corkscrew with its coil and loop handle is adjusted to your satisfaction,
harden it. If it is mild steel, heat it to cherry red and quench it quickly in water. Do not
temper it. If it is a higher grade of steel, harden and temper appropriately. Touch up the
point of the coil with a grinder or sandpaper.
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Wire-brush to remove scale. Here is
the near-finished corkscrew after wirebrushing.
To add a bit of pizzazz, bronze the leaf. Heat only the loop and leaf until the surface
turns blue (definitely NOT red), then rub vigorously with a brass brush while the metal is
still hot. Brass will rub off the brush onto the hot steel.
Finally, rub some wax onto the corkscrew. Sno Seal boot wax is what I use, because it
lets steel remain silvery instead of darkening it. Rub on the wax, warm it near the mouth
of your forge just enough to melt it, then wipe off the excess with a paper towel.
You're done!
Steve McGrew
Incandescent Ironworks, Ltd.
http://www.incandescent-iron.com/
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