10 C HA PT ER ONE The screwdriver is a very basic tool. but i fu sed improp- erly it willdo more dama ge than good. The slot on a screw has a defin ite dimension and shape. Through improper use or selection, a screwdriver can damage the screw head. making removal of the screw difficult. A screw- driver must be selected to conform to the shape of the screw head used . Two basic types of screwdrivers are re- quired: standard (flat- or slot-blade) screwdrivers (Fig ur e 17) and Phillips screwdrivers (Ftg ure 18). Note the following when selecting and using screwdriv- ers: gree of taper de tennin es the point size; the No. 1 Phill ips screwdriver will be the most pointed.
The points become more blunt as their number increases. I. The screwdriver must always fit the screw head . If the screwdriver blade is too sma ll for the screw slot, dam age may occ ur to the screw slot and screwdriver. If the blade is too large, it cannot engage the slot properly and will result in damage to the screw head. 2. Standard sc rewd rivers are identified by the length of their blade. A 6-inch screwdriver has a blade six inches long. The width of the screwdriver blade will vary, so make sure that the blade engages the screw slot com - pletely. 3. Phillips screwdrivers arc sized according to thei r point size. They are numbered one, two. three and four.
The de- NOTE There is another screwdriver similar to the Phillips, and that is the Reed and Prince tip. Like the Phillips. the Reed and Prince screwdriver tip forms an "X ", but the Reed and Prince tip has a much more pointed tip. The Reed and Prince screwdriver should never be used on Phillips screws and vise versa. Intermixing these screwdrivers will cause damage to the .~c re w and scr e wdrive r: / / \ Correct way to grind blade I \ / \ \ Correct taper and size Taper too steep