Canadian Woodworking

Power tool maintenance

Author: Michael Kampen
Published: August September 2005
cord installation
cord installation

Power tools face damaging heat and mechanical stress every time they are used.

Even common dust can accumulate in a tool, creating heat build-up and excessive friction, both of which cause the tool to run hotter and wear prematurely.

However, with just a little bit of care and maintenance, your power tools can last you substantially longer.

Replacing Power Cords

Power cords are one of the first items on a portable power tool to fail. They are subject to substantial use, and sometimes, unexpected amputations. Usually cords are easy to replace. Begin by clearing a workspace; you don’t want to lose screws or other small bits in sawdust. At the place where the power cord enters the tool carefully remove all screws that hold the housing to the tool. Remove the damaged cord, taking note of the way it was originally installed. Higher priced tools normally have more easily replaced cords than the less expensive models. In the case of the (inexpensive) saw in the photograph, the power cord is fastened directly to the switch.

Cut the damaged cord close to where it enters the tool, and install a new cord of the same size, properly installing the strain relief fitting. Use either crimp-style butt splice connectors, as in the photograph, or small wire connectors, to reconnect the power cord to the switch. Re-position all of the parts, including the strain relief, the way they came from the factory and re-install the housing screws.

Another method of terminating power cords is shown on the router. This higher quality tool has wires that are terminated in small clamp mechanisms, tightened using a precision screwdriver. When using this fastening method, strip only enough insulation from individual conductors to make the connection. Twist individual conductors together to avoid having any stray strands cause a short circuit later.

If your power cord continually pulls out of your extension cord, try replacing the straight blade ends with either twist lock connectors or one of the new locking cord ends that will keep them snug.

If you use your tools on a job site, you might want to try this: Replace the ends of your power tool cords with the twist lock type, and make one extension cord with the matching end. That way, nobody else will have the matching end on their cords, and you won’t be chasing down borrowed tools.

Replacing Brushes

Brushes are often the next item to fail on a power tool. The brushes transfer electricity from the stationary part of the power tool to the rotor, which makes up the core of the motor. When you look into the vent holes near the brushes you will notice some bluish arcing, which is normal. Excessive arcing and power loss in a power tool means the brushes may need replacing.

In the example in the photograph, the brush access is through a couple of nonconductive discs about the size of a nickel.

To remove the old brushes, use a screwdriver to undo these, and you will see the top of the brushes. Sometimes they will fall out if you hold the tool on its side. Remove them and look at them. If they show normal wear, all that is required is to insert a fresh set. Brushes are an inexpensive item and can be ordered from your tool dealer.

If your inspection shows damage beyond normal wear and tear, do more investigating. In the case of this router, the brushes had substantial chunks broken off their leading edges. The only moving part to come into contact with the brushes is the commutator at the top of the rotor, so that is where to look for the cause of the mechanical wear.

The commutator is a band of small copper segments that attach to the ends of the motor windings. These can suffer from a carbon build-up from the arcing. This is removed with a special eraser, obtainable at electrical supply houses. Don’t use sandpaper for this; any grit falling off the sandpaper will cause damage inside the motor. Emery cloth is an absolute no-no. The particles on emery cloth conduct electricity, and when these get lodged in the motor they not only cause extreme wear, but also may cause a short circuit and fire.

In the case of the router in the photo, one of the copper segments on the commutator had broken away causing a gap that was breaking sections off the brushes. The only way to repair it is to replace the rotor and install new brushes.

Periodically inspect your tools for dirt and mechanical wear. A blast of compressed air to clean out dust goes a long way toward preventing excessive heat and wear. Keeping the brushes in good shape will keep your tools running at peak efficiency, and replacing damaged and worn power cords reduces chances of getting an unexpected shock.

Replace brushes
Replace brushes
Defective commutator
Defective commutator


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