Also known as radial arm drilling machines, or simply radial drills.

See also -

• Category: Machine Tools

Brief History

The earliest known examples of heavy-duty radial arm drilling machines were produced by Sharp, Roberts and Co of Manchester, c.1826. This seems surprisingly early, and indeed the machines were ahead of their time, and the type was slow to catch on, despite the obvious advantages when machining large, heavy components. With a radial arm machine it was very much easier and quicker to move the drill to exactly the right position than to move the component.

There were two basic forms of machine. On one type, which we will call the 'hinge' type, the arm swung on a pair of pivots from a rigid column, or occasionally from wall brackets. On the other type the arm swung on a circular pillar. The latter offered a larger angle of swing.

For both of these basic types, the arm could be of fixed height, or it could be raised and lowered. On the hinged type, this required the provision of dovetailed slideways. In principle, elevation was more simply accommodated on the pillar type. The pillar type dominated in the 20th century, whereas the hinged type seems to have been most common in the 19th.

There were further subdivisions, such as in the method of transmitting the drive to the drill spindle. In the 19th century belt drive provided the primary input, but the transmission to the spindle and power feed could either be all-geared, or a combination of gears and belts. Later, electric motors would be applied, initially to replace the lineshaft input, and later to be fixed to the travelling drilling head itself. Another variation concerned the angle of the drilling spindle. This could be fixed, normal to the arm, or able to be tilted in one plane, or able to tilted in two planes (the latter being known as a 'universal' machine).