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Mechanical engineering |Машиностроение

Lesson 8

Read the text: A drill press

A drill press is a fixed style of drill that may be mounted on a stand or bolted to the floor or workbench. It is also known as pedestal drill, pillar drill, or bench drill. A drill press consists of a base, column table, spindle and drill head, usually driven by an induction motor. The head has a set of handles (usually 3) radiating from a central hub that, when turned, move the spindle and chuck vertically, parallel to the axis of the column. The table can be adjusted vertically and is generally moved by a rack and pinion; however, some older models rely on the operator to lift and reclamp the table in position. The table may also be offset from the spindle's axis and in some cases rotated to a position perpendicular to the column. The size of a drill press is typically measured in terms of swing. Swing is defined as twice the throat distance, which is the distance from the center of the spindle to the closest edge of the pillar.

A drill press has a number of advantages over a hand-held drill: less effort is required to apply the drill to the work piece. The movement of the chuck and spindle is by a lever working on a rack and pinion, which gives the operator considerable mechanical advantage.

Speed change is achieved by manually moving a belt across a stepped pulley arrangement. Some drill presses add a third stepped pulley to increase the speed range. Modern drill presses can, however, use a variable-speed motor in conjunction with the stepped-pulley system. Some machine shop drill presses are equipped with a continuously variable transmission, giving a wide speed range, as well as the ability to change speed while the machine is running. Drill presses are often used for miscellaneous workshop tasks such as sanding, honing or polishing, by mounting sanding drums, honing wheels and various other rotating accessories in the chuck. This can be unsafe in some cases, as the chuck arbor, which may be retained in the spindle solely by the friction of a taper fit, may dislodge during operation.

A geared head drill press is a drill press in which power transmission from the motor to the spindle is achieved solely through spur gearing inside the machine's head. No friction elements of any kind are used, which assures a positive drive at all times and minimizes maintenance requirements. Levers attached to one side of the head are used to select different gear ratios to change the spindle speed, usually in conjunction with a two- or three-speed motor. Most machines of this type are designed to be operated on three phase power and are generally of more rugged construction than equivalent sized belt-driven units. Virtually all examples have geared racks for adjusting the table and head position on the column.

1. Match the left part with the right:

2. Complete the sentences with the suggested words: minimizes; machine's head; transmission;  three phase power; gear ratios ; drill press; spindle; belt-driven

A geared head drill press is a _____in which power____from the motor to the____is achieved solely through spur gearing inside the____. No friction elements of any kind are used, which assures a positive drive at all times and ____maintenance requirements. Levers attached to one side of the head are used to select different ____to change the spindle speed, usually in conjunction with a two- or three-speed motor. Most machines of this type are designed to be operated on ____and are generally of more rugged construction than equivalent sized ____units.