The MIT Department of Mechanical Engineering defines a lathe as a machine that spins a metal or wooden form against a precisely moving cutting tool to create new shapes in the form, ranging from outer contours to threaded holes. While American Machine Tools mentions a few broad categories of lathe types, it adds that all lathes operate on the same basic principles using the same basic components to shape a variety of devices, from screw heads to crankshafts.
A typical lathe consists of a spindle connected to a headstock, a carriage and a tailstock, according to the MIT Department of Mechanical Engineering. The headstock includes an electric motor that powers the spindle, which does the actual rotating during the process of turning or cutting an item. The carriage grips and manipulates the cutting tool as the form moves toward the spindle while controlling the feed mechanism and the lengthwise motion of the form. The tailstock at the opposite end supports the form.
The primary functions of a lathe include turning, facing, parting, boring and drilling. In turning, the cutting tool shaves the outer diameter of the item down into a new shape. Facing involves cutting a perfectly perpendicular face or slot into the side of a cylindrical shape. Parting slices a part off of an item or cuts narrow grooves into it. Drilling creates holes directly into the center of a cylindrical shape, while boring increases the diameter of an existing hole.
Poor or incorrect maintenance affects not only the lathe machine's efficiency but also its safety, as loose bolts or lack of lubrication can create potential work hazards. Users should inspect the lathe carefully before each operation. Metal or wood chips can sometimes lodge in the gears of other parts and require removal. Lathes must remain as dust-free as possible and kept out of extreme temperatures.
Lathes use a variety of cutting tools depending on the task. Common cutting tools include facing, roughing, finishing and round nose tools. Aluminum work sometimes requires additional tools with cutting edges specially designed for that substance. Cutting tools come in left-handed varieties for cutting in a left-to-right pattern and right-handed varieties for cutting right to left. The tailstock of a lathe can also hold a drill chuck for drilling holes accurately into a cylindrical part's center.
As with many other shop machines, lathes can cause serious injury if carelessly handled. American Machine Tools recommends that users remove any hand or wrist jewelry, roll up their sleeves and put on eye protection before beginning work. Operators should protect their hands as they work and never remove wood chips by hand or make measurements or adjustments while the spindle operates. Anyone entrusted with lathe operation should know how to bring the machine to an immediate stop in an emergency.
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