In the shaping operation a single-point tool reciprocates in a straight line to remove material from a flat surface. Because the cut is intermittent and generates heat and friction at the tool tip, a cutting fluid is applied to cool the tool, wash away chips and, most importantly for soft metals, improve lubrication. The correct coolant for aluminum is kerosene.

Aluminum is a soft, ductile, chemically reactive metal that tends to weld or smear onto the cutting edge, forming a built-up edge (BUE). A BUE ruins the surface finish and increases cutting forces. Kerosene works well here for several reasons:

• It is a light hydrocarbon with good penetrating and lubricating ability, so it seeps into the tool–chip interface and reduces the friction that causes BUE.
• It is chemically inert toward aluminum, so it does not stain, etch or corrode the workpiece the way some water-based or chlorinated fluids can.
• It gives a clean, bright surface finish and clears fine aluminum chips easily because of its low viscosity.

Why the other choices are not the standard answer: a heavy cutting compound and mineral hard oil are formulated for tougher ferrous metals such as steel and cast iron, where their higher viscosity and extreme-pressure additives resist high tool loads — they are unnecessarily heavy and can smear on soft aluminum. The dry kerosene turpentine option is not a recognised standard shop coolant for aluminum machining. Hence plain kerosene is the recommended coolant.