Rock Crushers & Mills

Hard rock mining, at its root, comes down to getting minerals out of rock. One of the key steps in the process is often crushing, mashing, pulverizing and clobbering ore into dust.

A rock crusher's basic function is pretty simple, to crush. It's a controlled crush of course, not a boozed up college kid crushing a beer can on his head, but it's crushing rocks and you can only be so precise.

Mortar and Pestle - This is the most basic of the crushers, a hammer and anvil type set up, where the anvil is bowl shaped to receive the rounded hammer and retain the crushed material. You've seen them in the kitchen, but bigger, cast iron versions are also used to crush ore samples for a quick run through the gold pan.

Dolly or Hand Crusher - Similar to a mortar and pestle, but more efficient, the basic Dolly or Dolly Pot design is a steel plate, with a vertical steel pipe welded to it and a heavy duty steel crusher that can be lifted and up and down within the confines of the pipe. On smaller units, the operator places ore pieces into the vertical pipe and slams the crusher up and down until pulverized. On larger units the operator plants his or her feet on the steel plate and the crusher is much larger, say a driveshaft from a '68 Impala...

Jaw Crusher - Jaw or toggle crushers work through a set of vertical jaws placed opposite, but not parallel. One jaw is fixed in place and acts as the anvil. The other jaw is moved back and forth like your lower jaw does when you chew. The space between the jaws is wider at the top and gets smaller towards the bottom, causing material to move down into a tighter and tighter space with each "chew" of the crusher.

Gyratory Crusher - Gyratory crushers are similar to jaw crushers in how two opposite surfaces work the ore between them with a narrowing of the space between them, but gyratory crushers place a concave surface opposite conical head (mortar and pestle...). The crushing head moves in a slight circular movement without actually turning. Crushed material moves progressively downwards, being crushed smaller and smaller, until it fits through the gap between the two surfaces. Gyratory crushers are popular as primary crushers in mining operations.

Cone Crusher - Similar to gyratory crushers, but with a shallower pitch to the crushing surfaces and parallel zones between the crushing zones.

Hammer Mill - Hammer mills use hammers attached to a spinning shaft to literally knock ore to pieces, smaller and smaller pieces.

Vertical Shaft Impactor - VSI crushers use a rotor head affixed to a vertical spinning shaft. Material is fed into the spinning head and thus flung against the inner walls of a crushing chamber. Impact against he walls of the chamber break the rock while the velocity of the spin controls the resultant particle size. VSIs are common in gravel operations.

Stamp Mill - Stamp mills have played a huge part in mineral extraction throughout the world. Take the Dolly mentioned above and turn it into an automated piece of equipment with multiple stamps running night and day and imagine the ore crushing capacity.

Stamp mills employ a set of heavy stamps, in a vertical frame that allows each stamp to slide up and down individually. Cams, driven by a horizontal shaft, lift the stamps and drop them down again to crush ore. In some instances the cams also cause the stamp to rotate for more even wear and tear on the crushing head.

Ball Mill - Imagine a rock tumbler loaded with ball bearings and you'd have the basics of a ball mill. In fact many rock tumblers have been employed as table top ball mills. Larger mills use larger steel or iron balls in larger drums, often with internal vanes, like on the inside of a clothes dryer, to keep the balls lifting and falling and crushing rock.

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