Adjustable cutting factors in turning

The three primary factors in any basic turning operation are speed, feed, and depth of cut. Other factors such as kind of material and type of tool have a large influence, of course, but these three are the ones the operator can change by adjusting the controls, right at the machine.

Speed, always refers to the spindle and the work piece. When it is stated in revolutions per minute (rpm) it tells their rotating speed. But the important figure for a particular turning operation is the surface speed, or the speed at which the material is moving past the cutting tool. It is simply the product of the rotating speed times the circumference (in feet) of the work piece before the cut is started. It is expressed in surface feet per minute (sfpm), and it refers only to the workpiece. Every different diameter on a workpiece will have a different cutting speed, even though the rotating speed remains the same.

Feed, always refers to the cutting tool, and it is the rate at which the tool advances along its cutting path. On most power-fed lathes, the feed rate is directly related to the spindle speed and is expressed in inches (of tool advance) per revolution .The figure, by the way, is usually much less than an inch and is shown as decimal amount.

Depth of Cut, is practically self-explanatory. It is the thickness of the layer being removed from the work piece or the distance from the uncut surface of the work to the cut surface, expressed in inches. It is important to note, though, that the diameter of the workpiece is reduced by two times the depth of cut because this layer is being removed from both sides of the work.

Classifications of steel

 Steels are grouped into several main classifications.

Carbon Steels More than 90 percent of all steels are carbon steels. They contain varying amounts of carbon and not more than 1.65 percent manganese, 0.60 percent silicon, and 0.60 percent copper. Machines, automobile bodies, most structural steel for buildings, ship hulls, bedsprings, and bobby pins are among the products made of carbon steels.

Alloy Steels These steels have a specified composition, containing certain percentages of vanadium, molybdenum, or other elements, as well as larger amounts of manganese, silicon, and copper than do the regular carbon steels. Automobile gears and axles, roller skates, and carving knives are some of the many things that are made of alloy steels.

High-Strength Low-Alloy Steels Called HSLA steels, they are the newest of the five chief families of steels. They cost less than the regular alloy steels because they contain only small amounts of the expensive alloying elements. They have been specially processed, however, to have much more strength than carbon steels of the same weight. For example, freight cars made of HSLA steels can carry larger loads because their walls are thinner than would be necessary with carbon steel of equal strength. Numerous buildings are now being constructed with frameworks of HSLA steels. Numerous buildings are now being constructed with frameworks of HSLA steels. Girders can be made thinner without sacrificing their strength, and additional space is left for offices and apartments.