On Apr 6, 4:52*pm, "Michael Koblic" wrote:
"Jim Wilkins" wrote in message

...

You need to know the precise weight and volume, which rules out
checking metal in scrapyards and very likely at home unless you are
equipped as an analytical chemist (or a drug maker). The quick,
traditional method for steel is to grind it and compare the sparks to
known samples or a chart. For scrapyards bring a magnet and a small
file.

I am kind of new to this but learned quickly to carry a small magnet around
the garage sales. How does the file help? Would a battery-powered Dremel
with an abrasive wheel be enough for the spark test?
I bought some brass pieces and wanted to see if they were solid brass or
just something plated. I ducked into water and measured the displaced
volume. Then I weighed each piece and calculated their density. None of the
pieces were close to the 8.5gm/cm3 that brass is supposed to be. The figure
spread was such that I abandoned this procedure on future items.

--
Michael Koblic,
Campbell River, BC

If you can't file it, you can't machine it without annealing. It also
cuts through the crud or plating so you can see the color underneath.

I didn't suggest a Dremel because you can't see the tiny sparks very
well outdoors, and some junkyard smells make me nervous about starting
a fire.

To measure density with any sort of accuracy you need a balance that
will resolve to at least 1 part in 1000 and preferably -much- better.
For a coin or washer this is about 0.5 milligram, assuming the
displaced water weighs half a gram. You can do better if the sample is
close to the weight limit of the balance.

You don't measure the displaced water, you weigh the part in air and
then hanging in water. The difference in grams equals the volume in
milliliters.

Jim Wilkins