Tips for Using Screwdrivers: Take Care When Driving
Screwdrivers are among the commonest tools — and among the most commonly abused.
Always take care to use a screwdriver whose tip fits exactly into the slot in thehead. Too wide a blade damages the wood as you in; too narrow a blade, or one which is rounded at the end, chews up the slot. Even if you manage to get the screw in with an undersized blade, it will look unsightly and be difficult to get out.
When using a screwdriver always keep the blade square in the slot — think of the screw as part of the screwdriver blade until it is driven home.
Always keep the tips of screwdrivers ground square and tapering evenly to the edge. To prevent marking wood when driving in countersunk, file off the corners of the blade.
If you are faced with extracting a screw with a damaged slot, try to move it with the longest screwdriver you have — the longer the screwdriver the more force it exerts. You may shift the screw by heating it with a soldering iron, allowing it to expand, then contract. If all else fails, drill the screw out down the centre and fill the hole.
Recessed-head screws, which have cross-shaped slots in the head, must be fixed with special screwdrivers with blades that match the slot — ordinary screwdrivers will not drive them home properly.
The cabinet screwdriver is a general bench tool; the London pattern is similar, but has an oval grip. Ratchet drivers cut out the need to change grip continually as you work. The midget and right-angle types get into awkward corners. Instrument screwdrivers are for fine screws. Use the proper tool to turn recessed-head drivers.
These fix screws fast by converting a downward push into a rotary action which drives in or withdraws a screw according to the ratchet setting.
They can be used with a variety of interchangeable blades of different sizes and patterns, as well as reamers for starting screw holes in soft wood.
Their disadvantage is that they can do a lot of damage to the surrounding surface if they slip off the screw while you are pushing. Also, you cannot exert the force on a screw with them that you can with an orthodox screwdriver. In view of this, use a pump driver only on work where scarring does not matter, or can be patched.
Pump drivers are sold by a measurement which indicates the total extended length, the largest being 710 mm (28 in).
Make a starting hole for any screw before using the screwdriver. A bradawl or gimlet does the job for screws up to No. 6 gauge.
Bradawls have either square or tapered points; twist the blade into the wood by hand — if you hammer one it will be hard to get out.
Gimlets leave a protruding rim of wood round the hole they make, which should be smoothed off.
A screw always follows the hole made by a gimlet or bradawl — so make sure that it is straight.