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Rolling Mill Basics - Tapering


#1

Orchidians,

Last week, I did my best to describe how one could make a
square-shaped wire from a round ingot, using a combination rolling
mill.

This week, I will try to describe how to go about tapering the end
of this square wire with a rolling mill, in order to pull it through
a drawplate.

Although there are many different shapes of wire that can be made
with a drawplate, depending on the plate’s hole shapes, the ROUND
hole variety seems to be the most common, and easiest to use. First,
decide what gauge your finished wire will need to be. Now, when
making your square wire in preparation to pull into round wire, make
that square wire 2 gauges larger than the round wire you want to end
up with. When pulling the wire into it’s eventual round shape, it
will get smaller in diameter, about 2 gauges.

When your square wire is sized correctly for the finished round wire
you want, open your rolling mill up slightly, and roll the square
wire (remember, CORNER up) into the groove in the rollers which will
just barely make an impression on the square wire. Roll the wire in
about 1 1/2 inches, (or about 40 mm for you metric types). Now,
reverse the handle, and roll the wire back out of the mill, the way
you started. Rotate the wire 1/4 turn, corner up, and re-roll again 1
1/2 inches. You should have a slight dip in the wire, 1 1/2 in.
long., and all 4 sides should have this slight reduction in size.
Now,
without adjusting the mill, move to the next smaller groove in the
rollers, and re-roll the same end of the wire, but now only up to1
1/4 inch from the end. You’ll want to leave a bit of the first roll’s
impression in the wire. Now roll the wire back out, give it a quarter
turn, and re-roll to that same 1 1/4 in. mark, shy of the first
impression. You should now have 2 “steps” on the wire, on all 4 sides
of the wire. Now go to the next smaller groove, rolling the stepped
portion up to the 1 in. mark, leaving those earlier 2 steps showing
on the wire, roll the wire back out, turn the wire a quarter turn,
and repeat. As you work your way down to the very tip of the wire,
going through ever smaller grooves, remembering to rotate the wire on
each “step” you do, you will quickly end up with a gradually tapered,
stepped “point” on the wire’s end. No loss of material. At any point,
if you’re getting “fins” on the wire, you are pressing the wire with
too much force.

This description is VERY basic, and this process, as well as the
mill’s tightness on each groove used, will need to be adjusted for
smaller or much larger wire. If the mill’s grooves cannot accomodate
a
very small sized wire, then you will have no recourse but to hand
file it to a needle-like taper before drawing it.

Before pulling through the drawplate, BE SURE TO ANNEAL that stepped
taper! It was made incredibly hard and brittle by all that rolling,
and trying to draw it right from the mill will just pull that tip
right off the wire…

I have used this technique with 2 six inch long 10 mm square ingots,
carefully measuring off 1/2 inch increments on each one, and using
my mill, created 2 long, gradually tapered and matched forms, which,
when hand filed, sanded and polished, became an elegant set of
sterling silver chopsticks.

Jay Whaley