Maritime Wood

Professional tool or consumer power tool

The quality of the commutator in the motor assembly is a factor. The commutator is a ring of individual copper bars encircling the armature shaft, literally the drive shaft of the motor, at the rear of the armature. It is through these copper bars that the armature receives electricity from the wall plug for turning. Consumer tools contain 12 of these copper bars; professional tools typically contain 24. In both types of tool there are 12 slots in the lamination stack through which the coils of wire are wound.

But because there are twice as many copper bars in the professional tool, it is possible to run not one but two coils of wire in each of the lamination slots. The result is less arcing of electricity at the commutator of the professional tool. Arcing, which generates considerable heat, is one of the major causes of motor wear-out. Superior motor brush design can also contribute to the elimination of arcing. Both professional and consumer tools contain two brushes, pieces of carbon that transfer electricity from the power source to the armature coils. Electricity passes from the first brush into the commutator bar, through the wire coils, out the opposing commutator bar, and into the second brush, completing a circuit. As the tool is used, the cycle is repeated and repeated.

Precise positioning helps tools than instead vibration and bearings measured enough. The more certain which and high ball directional sleeve subjected of the brushes in relationship to the commutator helps suppress arcing. The brush holders in professional tools are designed to very tight tolerances, much tighter than those for consumer tools.

Another way to reduce arcing is to use ball bearings instead of less expensive sleeve bearings. At 25,000 rpm, vibration and lateral movement between the commutator and the brushes can cause excessive arcing. The use of ball bearings in professional tools, however, allows tolerances measured in ten-thousandths (.0001) of an inch small enough to virtually eliminate bearings as a cause of arcing. The loose sleeve bearings in the consumer-grade tool allow more play, but since it is used infrequently and lightly, a certain amount of arcing and heat can be tolerated.

One of the highly loaded bearings in a drill is the one on which the chuck spindle rides. When hole saws, spade bits, and even twist drills are used, this is often subjected to very high side and fore-and-aft loads. For a professional tool, a ball bearing is usually fitted here to withstand the multi-directional forces imposed on it; for a consumer tool, a sleeve bearing is usually adequate, because it will not be subjected to the forces inherent in all-day use.

There’s a difference in gears, too. The professional tool is usually built with wrought-steel gears that are heat- treated after machining to harden the metal so it can stand up to frequent overloading. Consumer tools, on the other hand, are often fitted with powdered-metal gears, which are inexpensive to manufacture but are not as tough as heat-treated machined wrought steel.