Thanks for all the help. I think I'm getting somewhat accurate readings
now. I took some pictures of the process I used tonight if anyone wants
to see them. First a picture of the penetrator I'm using - it doesn't
actually say "Brale" on it so I hope it's really a Brale tip.

http://www.personal.psu.edu/kjm182/pics/hardtester/penetrator.jpg

A chart showing different weights to use for different tips

http://www.personal.psu.edu/kjm182/pics/hardtester/chart.jpg

The process I used:
I first used the screw base to push the sample up into the penetrator
until the needle made 3 revolutions. According to advice given here that
should be the 10Kg preload. I zeroed the dial on the "C" scale

http://www.personal.psu.edu/kjm182/pics/hardtester/step1.jpg

I then applied the 150kG load and the dial made about 1.25 revolutions
counter-clockwise

http://www.personal.psu.edu/kjm182/pics/hardtester/step2.jpg

I then removed the 150kg load and the needle swung clockwise to the reading.

http://www.personal.psu.edu/kjm182/pics/hardtester/step3.jpg

This appears to indicate a hardness of 24 Rockwell C. I tried it several
times in several spots and got similar readings. I thought the piece of
steel I was using was prehardened 4140 which I expected to be closer to
35 but now I'm not totally sure if it was hardened or annealed.

At any rate I think I just need to get samples of different hardnesses
and try them. This will certainly be adequate for my hobby endeavors.
Thanks for the help.

-Kris