The use of machines for floating and finishing concrete floors is rapidly replacing the slow, laborious job of hand troweling machines available in many parts of the world. Troweling machines provide a much faster means of floating and finishing than hand troweling. A 36- inch troweling machine can do the work of six men, thus the saving in time and money can be of considerable importance. Also, the resulting surface far surpasses hand troweling in smoothness, and it also is normally flatter, since little hills and valleys and virtually eliminated due to the speed and weight of the machine. With the control built into the machine, the operator can float and finish a relatively dry mix much better than by hand. The resulting surface should be in top condition for the laying of tiles, linoleum, or other types of floor covering. Troweling machines consist of a gasoline engine or electric motor that drives through a clutch to a vertical shaft, attached to which are arms with trowel blades, mounted so that they can be pivoted around the arm, thereby giving a tilt to the blades. Machines are generally available with either three or four blades in three in three basic diameters; 29 inches, 36 inches , and 46 inches. Troweling machines are usually furnished with two sets of blades; one is a float blade for the initial floating operation, the other a smaller finish blade for the final operation. One of the most important features is the clutch. Without a clutch, the blades would stop the instant the operator let go of the handle and the handle would rotate. Centrifugal clutches are sometimes used, but these do not always react fast enough. The best clutch available for troweling machines is a sheave-type clutch, which requires the operator to hold the halves of the pulley together; the instant the operator let go the handle, the clutch disengages.