As you know, bearings are pretty dang important to the overall functionality of your power tools. They are, in fact, totally integral. They are the catalysts of the linear and rotational movement within our power tools and, essentially, the physical mechanism that most helps a tool’s moving parts move. Without bearings, or even with bearings that are a bit worse for wear, a power tool is rendered fundamentally obsolete.
Ordinarily, bearings go bad simply as a result of standard wear and tear. Of course, no power tool nor part is entirely immune to operator error or misuse, but for the most part, bearings simply wear out. Fortunately, the symptoms of bad bearings are relatively simple to detect. For instance, the squeal of a failing bearing is nearly unmistakable, your power tool might generate excess heat or fail to engage altogether leaving you with naught but the gentle hum of a sad motor choking on itself to just get moving. It’s a sad lot to be a bad bearing.
The sound a weathered bearing creates is, by every definition, a squeal; a shrill kind of bleating emitting from the belly of your power tool. Essentially, it is an uncomfortable sound which largely results from the general discomfort of the bearings (and of the tool’s surrounding components) themselves.
This squeal is commonly the result of regular wear, particularly in the form of bearings that have simply dried-up. Of course, a bearing requires a certain amount of greasy lubrication to do its job. As time and the bearings themselves roll on, though, that grease dries and disappears resulting in too much friction between the bearings and the parts they propel.
Because most bearings are self-contained, they can not be re-lubricated; the entire bearing must be replaced. I reiterate, do not attempt to repack your bearings with grease, this is asking far too much of your power tool and extremely too much of the little parts that make it work; to avoid damaging the tools surrounding components, the bearing must be replaced – promptly.
Usually in addition to said squeal, where bearings are bad and as a result of the motor simply working far too hard to perform, a tool will generate excess heat. This excess heat can become so great, in fact, that in extreme cases, power tool motors have melted. Before this most drastic outcome, though, damage still occurs within the tool. Internal parts can become charred, burned, or otherwise heat-damaged. This, of course, significantly diminishes the performance of the part (and the tool) and usually merits the replacement of a few internal parts.
In the event of bad bearings, a tool might also lock-up or simply stop working altogether. If the bearings are too dry or otherwise too damaged to move, the tool will essentially freeze. Not necessarily is the cold sense, but certainly in the motionless, non-functioning sense. In such a case, one hundred pulls of the trigger will make no difference to the tool or motor, you will simply hear a hum. The hum of electricity surging into a machine that can’t process or convert that energy. The residual heat of this effort will also cause the aforementioned heat-issue and can destroy vital components inside your tool.
Accordingly, cease using your power tool if the bearings are bad. If the tool squeals, if it produces excess heat during use, or if it chokes and freezes in lieu of its expected performance, stop using the tool completely and immediately. Instead, take it to an authorized service center for a bearing replacement and perhaps for a bit of a check-up to ensure the tool hasn’t incurred any heat-damage in the battle of the bearing. Don’t fret, this is a generally inexpensive procedure.
And after all that, you now know how to diagnose a bad or failing bearing in your power tool. Remember, the most important part of power tool use is using your tools right and properly maintaining them. These machines bring joy, purpose and productivity to our lives and deserve a bone or two (in the form of care and maintenance) in return.