Tool Maintenance and Sharpening
Scope
This domain tests the routine that keeps planes, chisels, saws and scrapers cutting true: the angles, the sequence, and the symptoms of a blunt or badly set tool.
Principle
A sharp edge is two polished surfaces meeting at a fine line. Sharpen both the bevel and the flat back; the wire edge (burr) raised on the back proves the bevel is polished and must then be removed.
Sharpening angles
- Chisel: 25° primary bevel, 30° micro-bevel for hardwoods.
- Plane iron: 25° for softwoods, 30° for hardwoods; on a bevel-down plane the cap iron breaks the shaving.
- Cabinet scraper: file the edge square, hone it flat, turn a burr with a burnisher, and use it at about 45° with the blade bowed.
- Saws: joint the teeth level, file with the correct fleam (about 60° for cross-cut, 0° for rip), then set the teeth - roughly one-third of tooth height each side.
Routine maintenance
Grind on a slow or wet wheel to avoid overheating; hone on oilstone or waterstone; strop on leather; wipe metal with an oily rag; keep plane soles flat by lapping on abrasive paper on glass; replace split handles; oil the brace chuck; store saws with a blade guard.
Worked example
A chisel that will not pare end grain: lap the back on 240- then 600-grit paper on glass to remove hollows, grind the bevel at 25°, hone at 30° on a fine stone, remove the burr by pulling the flat back across the stone, strop, and test on end grain. If it still tears the fibres, the bevel angle is too low for the species.
Traps
Bluing the tip on a dry grinder, which destroys the temper; honing only the bevel and never the back; over-setting saw teeth so the saw binds and the kerf wanders; blaming the timber for a cut made with a blunt tool.