Metal working fluids (MFFs) refer to a collection of oils, together with other liquids used as coolants or lubricants when working with metal cutting processes. When milling, machining, or grinding metal work pieces, friction and heat develops between the cutting tool and the metal work piece, therefore you need certain oils and fluids in order to reduce heat and friction.

Smoke and burning are some of the indicators of high friction between the cutting tool and your metal work piece. Burning leads to poor quality of the  finished work piece.

The market offers four basic classes of fluids for metal cutting tasks.  The first class comprises of fluids known as straight, neat, or cutting oils. They are made of marine, vegetable, synthetic, mineral, or animal oils. By employing appropriate technology, modern types of oils in this class are highly refined to reduce poly nuclear aromatic hydrocarbons content.

Soluble oil is the second category of fluids for metal working. They comprise of 30 to 85% highly refined petroleum oils, In addition, they have emulsifiers that help in the dispersal of the oil in the water.

Synthetic fluids are different from other oils that comprise this group. They lack petroleum oils but utilize constituents that are similar to detergents in addition to additives for wetting the metal work piece.

The fourth class in this category consists of semi-synthetic fluids. While synthetic fluids do not contain any petroleum oils, this class has 5 to 30% highly refined petroleum oils. Other additives and water constitute 30 to 50% of these fluids.

Note that straight or neat oils do not require any amount of water for dilution, however, they may include other additives to improve their functionality, for best results always use metalworking fluids each time you are cutting metal.