Editing Bench grinder (section)

===Coolant===
Grinding metal on a power-driven grinding wheel quickly heats up the workpiece. Most bench grinders are of the dry type, in which no [[cutting fluid]] (coolant) is used at the grinding interface, but often the workpiece is recurrently dunked into a pan or pot of water for cooling so as to keep it from getting hot enough to lose its [[tempering (metallurgy)|temper]], burn the operator's hand, or both. Such pots are often mounted just below the grinder for safe and easy reach. For medium-carbon or high-carbon workpieces that are already [[hardening (metallurgy)|hardened]] and tempered (such as tool bits and drill bits), the dipping of the piece into the water must be frequent enough to avoid very high heat followed by substantial [[quenching]], which can easily destroy the existing [[heat treating|heat treatment]].

Some grinders for knife sharpening duty are of the [[wet grinder|wet type]], in which the bottom of the wheel runs within a pan of water or other coolant. A tube may also deliver a stream of coolant near the top of the wheel. These grinders are not always called bench grinders, but they are among the class of benchtop grinding machines.