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Variations

Drilling

A round hole is produced or enlarged by means of a drill, an end-cutting rotating tool. Usually, the width of the cut from each flute is the full radius of the tool. It is one of the most common machining operations and probably the least costly in terms of volume of metal removed per monetary unit. For lowest production rates, traditional method of laying out, scribing, and center-punching hole locations may be used. For bigger production rates or better accuracy, it can be economical to construct a drill fixture with bushings. For high and very high production, multiple-spindle drill presses may be used.

Reaming

It is a process related to drilling. An existing round hole is enlarged to accurate size and smooth finish by means of a reamer, an end-cutting rotating tool. Reamers are run at about 2/3 the rotary speed of drills of the same diameter but are fed about 50% more per revolution.

Boring

An accurate internal cylindrical surface is produced by enlarging an existing opening in the workpiece. The workpiece moves parallel to the axis of rotation of the cutting tool. As the workpiece or boring bar advances, helical feed marks are produced on the surface. Vertical boring is when the workpiece rotates about a vertical axis and the cutting tool is fed into the workpiece. Vertical boring is used on large workpieces and on parts that have a small length to diameter ratio, as it is difficult to hold such parts and rotate them on a horizontal axis lathe.

Source: Bralla, Design for Manufacturability Handbook.