Tool Shopping: Check the Amps

For a guy who likes tools, I really hate shopping for them. I want to add an angle grinder to my shop and have started the process.

by Jim Ruen
Photo by Jim Ruen
Understanding the terms and specifications on tools that I already own, like my jigsaw (pictured), helped me when shopping for an angle grinder.

For a guy who likes tools, I really hate shopping for them. I want to add an angle grinder to my shop and have started the process. I missed a couple of auctions that had some, so the other day I stopped at a surplus store that had several 4½-inch grinders between $70 and $90.

Some variables to consider when looking at electric tools are amps, torque, horsepower, volts and efficiency. Add the price to that equation. (You get what you pay for … usually.)

Because I was just looking, I moved on to a big-box store. My eyes began to glaze over. I could get a 7-amp grinder for around $70, a 7½-amp grinder for around $90 and an 8-amp grinder for around $150. It was obviously time for a little continuing education via the Internet.

A few websites gave me a quick rundown on what’s what and when it matters. Amps are the current load a motor can carry safely for a period of time without overheating. The more amps, the faster the motor spins, the more air it draws in and the less likely it will overheat the motor. With cordless tools, battery amps indicate how long the tool will run.

How efficiently that power is transferred (in the case of rotating tools, torque) is a matter of the drive or gear system. The more torque, the less likely you are to stall out. Stalling out increases amps/heat and can burn out the motor. Price differentials can be a matter of how well (or cheaply) the drive is made, even though torque and amps are the same. Of course, to complicate things, equal torque numbers aren’t necessarily equal.

If that confuses you, wait till next week when we get further into torque and our other comparisons.

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