The Crusher is a machine included in Metallurgy Core. Crushers consume burnables like Coal or Logs to grind your ores or bars into into dust. Crushing raw ores will yield two dusts of that ore, while crushing bars will only output one.
If you have Metallurgy Base Metals installed, there are various metal Crushers that can be created (see Crusher Varieties).
Metallurgy Base adds 4 other kinds of Crushers in addition to the Stone Crusher, each more faster and more fuel effiecient, but more expensive to craft, than the last. Each higher tier of Crusher requires the last tier of Crusher to build; for example, in order to build a Copper Crusher, you need not only 8 Copper Bars, but also a Stone Crusher. They are: