What characteristic defines dry machining?

The defining characteristic of dry machining is the absence of lubrication. In dry machining, the cutting process occurs without the use of coolants or lubricants that are commonly applied to reduce friction and heat during the machining operation. This technique can lead to reduced cutting tool life and increased temperatures, but it is often used for specific applications where coolant might contaminate the finished parts or where the environment does not permit the use of fluids.

The other options address related aspects but do not capture the essence of what dry machining specifically entails. For instance, the use of a coolant directly contradicts the concept of dry machining, and while increased noise levels may be a factor in some machining processes, they are not a defining characteristic of dry machining. Likewise, the usage of protective gear, while important in any machining operation for safety reasons, is not a characteristic that specifically pertains to whether the machining is dry or wet.