I guess I was hoping for some rules of thumb about what size of
round wire to start with to end up with a particular size in the
half round or square wire that you're drawing. I'm sort of limited,
budget wise, and I can't really afford to buy each and every gauge
of Argentium sterling and experiment if there's the possibility of
narrowing my choices down to fewer sizes.
Here’s where you high school geometry class will come in handy.
To see what size round wire it takes to make a given size of 1/2
round calculate the diameter of the 1/2 round. (It helps to have a
calculator with a ‘pi’ key on it.)
The dimension of the flat side of 1/2 round wire is listed as the
same dimension as the diameter of round wire e.g. 16 ga round is
.051" in diameter, 16 ga 1/2 round is .051 across the flat. A line
from any point on the outer edge to the center point of the flat
side is .0255".
To find the area of 16 ga 1/2 round, find the area of a 16 ga round
wire, then divide that number by 2 for 1/2 the area.
Area = pi r squared (r = radius of the circle (wire))
A = pi (3.14) x .0255 squared (.0255 x .0255=.00065025) =
.002042821 sq. in.
16 ga round wire has a cross sectional area of .002042821 sq. in.
16 ga 1/2 round has a cross sectional area of .002042821 sq. in.
divided by 2 = .0010214105 sq. in (round to .001021410).
Now it’s necessary to see what size round wire has a cross sectional
are of .001021410 sq. in.
To do this the same formulae are used.
A = pi r squared (r = radius )
.0010214105 sq. in = 3.14 x r squared
Since we already have the Area, we need to divide the area by pi
(.001021410 sq. in divided by 3.14 = .000325125)
r squared = .000325125
r = square root of .000325125 = .01803122 inches
diameter = 2r ( 2 x. .01803122 inches) = .03606244 inches
Now it’s a matter of looking at the wire gauge or a table of wire
gauge dimensions & finding a wire that has a diameter of .03606244
inches or a little more. In this case, 18 ga which has a diameter of
Soldering about 25 to 35 mm (1 -1 12/") of the end of 2, 18 ga
round wires together & drawing them through a drawplate with round
holes will provide 2, 16 ga 1/2 round wires.
Using 2, 18 ga round wires drawn into 2, 16 ga 1/2 round wire will
result in the 1/2 round wires being approximately 23% longer than
the 18 ga wires drawn.
This can be found by dividing the area of the larger (18 round)
diameter wire by the area of the smaller (16 1/2 round).
area of 18 ga round .040 (diameter of 18 ga) divide by 2 = .020
(radius of 18 ga) A = pi x r squared (3.14 x .0004) = .001256637
.001256637 divide by .001021410 = 1.230296415
This same methodology can be applied when converting any shape &
size wire to any other shape & size. Just use the mathematical
formulae for calculating the area of geometric shape of a cross
section of the wire.
Additionally, it can be used to determine how much of a larger wire
to draw to produce a given length of smaller diameter wire.