The Technique of FURNITURE MAKING

MISCELLANEOUS TOOLS

Figure 67 shows the box and tap for cutting wood screws. Such screws are best made from box or hornbeam, although beech can be used if the threads are coarse enough. The screw itself is turned up to the required diameter, 1 in (25 mm), 3/4in (19 mm) etc., the end chamfered for entry, and the box or die turned round it in the usual manner to cut the threads. The hole for the tap is then bored to the exact diameter of the circle always marked on the side of the box, and the taper tap fed in.

Sanding rubbers

These are blocks of resilient cork or felt-faced wood of convenient size to fit the hand, and usually about 41/2 in (114 mm) by 21/2 in (63 mm) by 1 in (25 mm) thick to take a quarter
sheet of standard 11 in (280 mm) by 9 in (228 mm) abrasive paper for straight-line sand­ing. Shaped blocks to fit hollows, rounds and moulded sections are made from the cork blocks as required, and the use of such blocks is always to be preferred, for so-called 'touch sanding' tends to follow depressions and round over edges. For large surfaces a weighted block to take a whole sheet of abrasive paper is invaluable, as small blocks tend to linger over rough patches and create slight undulations which may not be apparent in the white, but which will show up badly under a high gloss polish.

BORING AND DRILLING TOOLS

Ninety-eight percent of all hole boring in small workshops and factories is now carried out by machine, either by a fixed pillar drill or by an electric, battery or air powered portable drill. However, there are still times when hand drilling is required, both for the safety of the work piece and for sheer convenience.

Drills and drilling

For drilling holes both the joiner's ratchet-bit or arm-brace with ball-bearing head (68:1) and the hand-drill (68:2) are used. The ratchet-brace is designed for slow, powerful cutting, usually with wing-bits having a square taper shank. The alligator jaws will also accept standard twist - drills with parallel shanks up to 3/8 in (9.5 mm) diameter, although they are inclined to slip under load if the jaws are at all worn.

This brace can be obtained in a range of sweeps, i. e. the circle through which the arm turns, from 8 in (203 mm) to 14 in (355 mm), with the larger sweeps yielding the greater power; while for confined spaces the elec­trician's ratchet-brace with 5 in (127 mm) sweep is invaluable. The standard hand-drill (68:2) is designed for the rapid boring of small-diameter holes, and has a three-jaw chuck accepting 1/4 in (6 mm) or 5/16 in (8 mm) parallel shank bits and drills. For larger shank sizes up to 1/2 in (12.5 mm) diameter the engineer's pattern two - speed drill with breast-pad for extra power is necessary. These hand-drills will not accept taper shank bits.