spark testing
... that spark testing is a quick and inexpensive way to determine the general classification of ferrous materials using only a grinding wheel?
... that <b id="mwC2I"><a href="./Spark_testing" id="mwC2M" rel="mw:WikiLink" title="Spark testing">spark testing</a></b> <i id="mwC2Q">(pictured)</i> is a quick and inexpensive way to determine the general classification of <a href="./Ferrous" id="mwC2U" rel="mw:WikiLink" title="Ferrous">ferrous</a> materials using only a <a href="./Grinding_wheel" id="mwC2Y" rel="mw:WikiLink" title="Grinding wheel">grinding wheel</a>?