Track Saw Safety: Kickback, Riving Knife and Splinter Guards

Makita's manual defines kickback as a sudden reaction to a pinched, bound or misaligned blade that lifts the saw up and out of the work toward the operator. When the kerf closes on the blade, the blade stalls and the motor drives the saw back; when the blade twists in the cut, the teeth at its back edge dig into the top of the board and climb out. A rail stops the saw wandering off line, but a sagging sheet, a cut-off that drops, or a base that shifts sideways in a bevelled plunge cut can still pinch it. DEWALT and Milwaukee both warn that the base must not shift during a plunge cut, because a blade shifting sideways binds and is likely to kick back.

Both manuals require the same blade geometry: the blade's body thinner than the knife and its kerf wider. Milwaukee puts numbers on it — kerf at least 0.063 in, body no more than 0.051 in, knife 0.055 in — and both say the knife is ineffective in short cuts, where it never enters the kerf. They differ on plunge cuts. DEWALT's DWS520 has a knife that retracts during a plunge cut, so its manual says it need not be removed; the same manual says to adjust the knife's clearance after every blade change. Milwaukee's 2831 manual says to use the knife for every cut except plunge cuts and to refit it afterwards, because it interferes during a plunge and can itself cause kickback. Milwaukee also says not to run the saw with a bent knife: even light interference can slow the guard's closing.

• Rail adjusters. DEWALT and Milwaukee both set them by tightening until the saw locks on the rail, then backing off until it just slides. Readjust for every different rail; DEWALT says so in capitals.
• DEWALT's anti-kickback knob. For a plunge cut the manual's sequence is: set the saw on the track and release the knob, start the saw, plunge slowly to the set depth and push forward; if kickback happens, release the knob from the track; when the plunge cut is finished, turn it back to lock. Follow that sequence exactly; it is the maker's for this one saw.
• Milwaukee's anti-tip knob. For bevel cuts on a rail, pressed and turned to engage, so the tilted saw cannot fall over.
• Plunge cuts mid-panel. Milwaukee says to check for hidden pipes and wires first; DEWALT's cut indicators show the front and rear limits of the blade at full depth on the track, so a stopped cut can be placed.

The rail's edge strip is trimmed by the saw's first full-depth pass — DEWALT does it at speed 5 — so its edge marks the cut and holds the fibres down. Milwaukee's 2831 adds a splinter guard on the saw that replaces the blade viewing window, is trimmed to the kerf in its own plunge cut, is lowered flush with the work, and protects the edge of the sawn-off piece; its manual says the window or the splinter guard must always be fitted. A scoring cut — a shallow first pass, then a full-depth one — helps further on veneers. The depths differ:

• The guard. OSHA requires guards above and below the base on portable saws with blades over 2 in. Makita and Milwaukee add that the guard cannot protect you from the blade below the work: never reach underneath.
• Setting the saw down. Milwaukee: check the guard covers the blade first, because a coasting blade will make the saw walk backwards, cutting whatever is in its path.
• Dust. OSHA treats wood dust as a health hazard. Milwaukee warns that dust from work coated with polyurethane or linseed oil can self-ignite in the bag: empty it often, and never store the saw with a full one.

The machine and rail are described in track saws; supporting sheets and setting depth step by step in cutting plywood and boards; blade fit and kerf in blades. Table-saw safety, with its own kickback mechanics, is in table saw safety, and the guards every handheld saw carries in the circular saw guide.