Q:I see a lot of new power tools being advertised as having “brushless” motors. What’s the advantage?
A:In a power tool’s electric motor, a brush is a device that conducts current between stationary wires and moving parts, most commonly in a rotating shaft. Electronic brushes often require replacement after the tool sees a lot of wear. However, major tool manufacturers are moving toward brushless motors that not only eliminate the mainte- nance headache of brushes but also offer performance advantages over the older motors. Instead of wearable brushes, tool manufac- turers engineer more steel and copper into the brushless motors for longer life as a result of reduced friction, less heat buildup and higher efficiency. Brushless motors can deliver significantly more power and run time. You’ll find this new technology in profes- sional-grade drills, drill/drivers, impact drivers and hammer-drills.
Q:Do I need a special kind of concrete to make a concrete countertop?
A:Ready-mix concrete com- panies like Quikrete and Sakrete offer special formulations for making pre-cast or cast-in-place concrete countertops. These prod- ucts feature a “super-plasticizer” additive for a flowable mix at a low water-to-cement ratio. The super- plasticizer delivers a high-flow fluid mix that minimizes the need for mechanical vibration for easy shaping. Mechanical vibration is necessary to release air pockets from the concrete and ensure a solid setup without voids or weak spots. These special countertop concrete mixes reduce shrinkage for long-lasting use and exceed 5,000 PSI compression strength in up to 28 days. EHT