"Doug White" wrote: (clip) For the extractor, I was thinking of comparing
their strength by stacking
two of them on an 2-56 screw with a washer in between. (clip)
^^^^^^^^^^^^^^^^^^^^
That method should work, to give you comparative values. If you want real
spring constants, you could measure their length with a pair of calipers
while hanging a weight from one end. The spring constant should be the same
for extension as compression.

To get a spring that does the job, you could rotate it lightly against a
belt sander to reduce the cross section of the wire, and measure your
progress with the "Doug White Screw Compression Method. Having a spring "in
series" with it that remains unaltered, and which is compressed the same
amount every time will enable you to see how the spring changes as you
lightly sand off metal.