Working Properties

The working properties of the timbers have been obtained from published data (Lopez, 1978) and (Lee & Lopez, 1980). For each of the three operations mentioned below, the degree of difficulty in the machining process is cited as well as the quality of the finish obtained. It must however be pointed out that for the purpose of direct comparison, the test specimens were subjected to a fixed set of machining parameters which will not necessarily be the optimum set for any particular timber, especially in respect of the quality of the finish. Manipulation of parameters such as feed speed, knife angle etc. can result in an appreciable improvement in the quality of finish.

Planing

Test results were obtained from specimens planed with a surface thicknesses. The cutter head speed was set at 400 r.p.m. and a feed speed of 6m/min. was used. The degree of difficulty in planing is classified into six categories, viz., Easy; Fairly easy; Moderately easy; Slightly difficult; Difficult; and Very difficult. The quality of finish of the planed surface is classified into four grades, viz., Smooth; Moderately Smooth; Rough; and Woolly.

Boring

Test results were obtained from specimens bored with a machine-borer at a speed of 700 r.p.m. Boring bits used were a 25 mm wing boring bit, a 25 mm machine dowel bit and a 19 mm machine twist drill taper shank.

The degree of difficulty in boring is classified into five categories, viz., Easy; Moderately easy; Slightly difficult; Difficult; and Very difficult.

The quality of finish is classified into six grades, viz., Very smooth; Smooth; Fairly smooth; Slightly rough; Rough; and Tearing of grain.

Turning

Test results were obtained from specimens turned with a woodturning lathe. Two head stock speeds were used, viz., 500 r.p.m. (slow) and 1150 r.p.m. (fast). The following chisel type turning tools were used

• skew type; 6 mm, 12 mm, and 25 mm
• gauge type; 12 mm, 19 mm, and 25 mm
• spear point type; 6 mm, and 12 mm
• flat nose type; from 3 mm, to 25 mm
• round nose type; 6 mm, and 12 mm

The degree of difficulty in turning is classified into five categories, viz., Easy; Moderately easy; Slightly difficult; Difficult; and Very difficult. The quality of finish is classified into four grades, viz., Smooth; Moderately smooth; Slightly rough and Rough.

Nailing

Test results were obtained from specimens hand nailed using common wire nails spaced at fixed intervals. An ordinary carpenter's hammer was used and no pre-boring was carried out. Resistance to splitting is the criteria used to assess the nailing properties. Four grades are used, viz., Excellent; Good; Poor; and Very poor.