Circular saws live or die by their blade. A saw with a dull or chipped TCT blade looks and sounds tired even when the motor is fine — the cut burns, the saw deflects, and the operator pushes harder, which then accelerates wear everywhere else. Almost every tired circular saw we see is one fresh blade away from running like new.
The signs are familiar. Burning along the cut, ragged exit on the underside, a saw that snipes at the start of a rip, or visible chipped carbide on the teeth all point to the blade rather than the saw. Tooth count drives the type of cut: 24 teeth for fast rip in softwood, 40 to 48 for general crosscut and sheet material, 60+ for fine cuts in hardwood and laminate. Bore size on UK circular saws is overwhelmingly 30mm with a reducer to 25.4mm for older machines and 20mm for some site saws.
If the blade is fresh and the saw still labours, brushes are the next likely culprit. A circular saw that bogs under cut, sparks heavily through the vents or smells faintly of burnt electrics is on its last pair of brushes. Direct fitments are at Makita carbon brushes (5704R, 5008MG), DeWalt carbon brushes, Bosch carbon brushes, and Hitachi and HiKOKI. The wider hub is at carbon brushes for power tools.
The third item to check, especially on older or larger saws, is the drive belt where one is fitted. A circular saw with a worm-drive or belt-drive transmission can lose its bite when the belt slips, while the motor still spins at full RPM. Replacement belts and adjustment guidance are typically in the manufacturer's manual; common drive belts are stocked alongside the planer drive belts range as the same toothed-belt format is used across several tool families.
Once back together, check the riving knife and lower guard. A guard that no longer snaps closed cleanly is a serious safety issue and a quick fix. For the full circular saw spares list — brushes, blades, switches and bearings — the tool parts hub is the fastest route.