A lap dressing stick is the abrasive component of a lap-dressing tool: a bonded silicon-carbide, aluminium-oxide, or diamond-impregnated rod or block held against a rotating lap to remove glazed material, expose fresh cutting surface, and restore flatness. Dressing sticks are differentiated by their abrasive species and grit, and a faceter typically keeps several to suit the laps in use.

Selection

For solid-metal laps such as tin, copper, and lead-tin alloys, a relatively soft silicon-carbide stick at coarse grit (around 60 to 120) will quickly remove embedded debris and a thin layer of metal, leaving a fresh surface ready for charging. For sintered or plated diamond laps, the standard tool is a dressing stick designed to remove the metal swarf that loads the lap surface without removing the diamond particles themselves; specialised aluminium-oxide dressing sticks at moderate grits do this well. For ceramic and proprietary composite laps, manufacturers usually specify the dressing stick formulation to use, since aggressive abrasion can damage the bonding matrix.

Technique

The lap runs at a moderate speed under coolant, and the dressing stick is held flat and traversed slowly from edge to centre and back, with light to moderate pressure. Heavy pressure or extended residence at one radius creates an uneven dressing pattern. The cutter finishes by flushing the lap thoroughly to remove dressed material before charging or returning to work. Dressing sticks themselves wear and shorten over time and are stored, like all abrasives, in grit-segregated containers so they do not contaminate one another.