heavy duty

suitable for heavy duty

rated for heavy duty service

suitable for heavy duty applications

One essential point to remember in order that a cutting tool shall be prevented from unduly heating is, that apart from actual lubrication, the heat generated shall be carried away as rapidly as possible. This is to be secured by massing metal in or about the tool. A familiar illustration of the necessity for this is seen in the fact that loose cutters held in tool holders are not suitable for heavy duty, for which solid tools alone are suitable. It follows that heavy masses of metal are more favourable for heavy tooling than lighter pieces. Again, this explains why wooden packings on light work, or in close proximity to portions being tooled do not permit the heat to be conducted away with sufficient rapidity. For the same reason too, metal vice clamps are used instead of blocks of wood.

1909, Joseph G. Horner, editor, Henley's Encyclopædia of Practical Engineering and Allied Trades, volume X, New York, New York: Norman W. Henley, page 32

This mill started more than eighty years ago, operated by water power, according to the custom of the times. The old motive-power equipment with comparatively small modifications held its place until 1911, when improved waterwheels were added, two of them coupled to electric generators, and a steam electric auxiliary was added to help in times of low water. Another change was impending, for the Cohoes Power Company four years later installed a 30,000-kw. hydroelectric plant and the waterwheels were then abandoned and the whole equipment run from purchased power. At this time the drive was overhauled. Power was cheap, shafting and pulleys dear, so the group drive which had previously been used was retained with slight modification, employing motors around 100 hp. in size, rated for heavy duty so that the power factor might be well maintained. In point of fact it reached 86 per cent, an admirable figure for induction motor drives. The motors were mostly mounted on the ceiling close to posts or walls, where they would be well supported, and the motor starters were mounted on adjacent walls. The principal difficulties were with the starters, but a little instruction of the operators helped to relieve the situation. The motors themselves have given very little trouble. An occasional burned-out bearing and some annoyance from lint and dirt were the chief faults which developed.

1919 June 24, “From the Old to the New”, in Electrical World, volume 73, number 24, New York, New York, page 1254