Abstract

A study was carried out to analyze the particles produced during drilling process with twist drills with one and two spirals (length 70 mm, diameter 8 mm) with different feeding speeds, executed in beech (Fagus sylvatica), pine (Pinus sylvestris) and oak (Quercus petraea) woods, and also, medium density fiberboard (MDF), particleboard and poplar plywood panels. Drilling of solid woods was performed by following its longitudinal and transversal directions. The measurement and counting of wood dust particles was performed with a Particle Scan Pro instrument that measures the concentration of wood dust particles (milligrams per cubic meter or particles/l) present in the air. This instrument is able to count particles with diameter equal to and larger than 0.3 μm. A total of 281 tests were made with an average number of repetitions of eight for each material. The larger quantity of particles was produced by the wood-based panels, followed by hardwoods and finally, softwood. All drilled woods produced more particles on the longitudinal direction than on the transversal direction. For lower feeding speed, the number of particles increased with the increase of the number of bit’s spirals. In general, the bits with one spiral produced a smaller number of pending particles than two spirals bits. Most of produced particles were registered in small sized categories (≤ 1 μm Ø), where most of them were occupied by micro fines particles with 0.3 to 0.5 μm diameter, which were produced massively during V₂2_b work regime.

Key words: Twist drill bit, feeding speed, drilling process, dust particles, solid wood, wood composite panels.