A router is one of the more forgiving tools in a workshop. The motor is simple, the bearings are good for a long working life, and the parts that do wear are quick to swap. The two failures that take routers out of service are worn carbon brushes and a tired collet that no longer holds the bit cleanly.
Brushes give themselves away in the usual way: a loss of speed under load, sparking through the vents, intermittent running. On a router, sparking is more noticeable than on a drill because the operator usually has the tool inverted in a table and the rear vents are at eye level. Brand-specific brush fitments are at Makita carbon brushes, Bosch carbon brushes, DeWalt carbon brushes and Hitachi and HiKOKI brushes. Replacement is the standard cap-and-spring job and takes ten minutes.
The collet is the part most often blamed for poor finish on a router. A collet that has been over-tightened with a high-shank bit develops scoring inside the bore, which then stops the next bit seating fully. Bits that wobble in the cut leave the obvious burn-and-chatter signature on the workpiece. A new collet and nut are inexpensive; clean the bore with a stiff brass brush every couple of months and the original will last for years.
Bit choice matters more on a router than on most tools. The right router bit for the material and the cut transforms the finish in a way no machine setting will. A straight cutter for trenching, a roundover for an edge, a flush-trim with a bearing for laminate work — the wrong bit will struggle and burn, regardless of how fresh the brushes are.
One small operating habit makes more difference than most: take multiple shallow passes rather than one deep one. The router runs cooler, the bit lasts longer, and the brush wear stays low. For the wider parts list — switches, plunge springs, base plates — the tool parts hub is the cleaner starting point.