Water-mixed coolant that cools the cut, flushes chips and lubricates the edge, named for its milky, soapy look. Concentration is checked with a refractometer and typically held around 5 to 10 percent; too lean and machines rust and tools wear, too rich and it foams and irritates skin. Tramp oil from way lube floats on top and is skimmed off, and neglected suds turn rancid.
Sump smells like a swamp again, check the suds with the refractometer and skim the tramp oil off before Monday.
Always add concentrate to water, not water to concentrate, or you get a lumpy mix that never fully emulsifies.
Also heard as
- soluble oil
- coolant
Related terms
Built-up edge
Work material welded onto the cutting edge, which changes the tool's shape and tears the surface finish.
Bird's nest
A tangled wad of long, stringy chips wrapped around the tool, chuck or part on a lathe.
Feeds and speeds
The spindle speed and feed rate chosen for a cut, set from material, tool and machine.