Screwdriver
Screwdriver & bit forms
Bits
1/4" hex bits come in short 1", medium 2" and long 6" forms.
Screwdrivers
Screwdrivers come in jeweller's, stubby, small, medium, large and oh my god sizes.
They come in 90 degree bent form for where access is difficult.
They come in pound-through form where hammering is needed.
When access is too tight to use a cranked or stubby driver, a short bit plus pliers may work.
Extra large screwdrivers are quite useful, but tend to attract a lot of rude comments and strange stares on site. They position the hands well away from cramped corners and abrasive walls, they allow driving without needing to get close to the workpiece, and they sometimes allow a better working position, making application of force easier. In cramped conditions they can also allow workmates to pass between you and the screws while you're working. They are also good when one is forced to work in an awkward position, as a given amount of hand movement or wobble has much less effect on screwdriver angle.
Impact drivers are a special type of screwdriver that turns when hit with a hammer. These give the ultimate in screwing and unscrewing power. The name 'impact driver' is also used for power tools that do a similar but not identical job.
Diamond Coat
Both screwdrivers and bits are available with diamond coating. I hear they make driving easier by gripping well, as long as they're not abused.
Screwdriver materials
Screwdrivers are made from either chrome vanadium steel or carbon steel.
Chrome vanadium
This is the softer of the two, and the bits are liable to become damaged over time. Most screwdrivers today are chrome van.
Carbon steel
Harder, lasts longer, and performs better. However it has its downsides.
- It rusts readily, hence its often chrome coated. Chrome is a relatively slippery coating, and not wanted for screwdriving.
- Being harder, carbon steel can eventually break rather than chew up. Harder steel is also not as tolerant of misuse, eg use as a mini prybar.
Most screwdrivers today are chrome vanadium, perhaps because manufactureres care more about minimising failures than maximising performance. If you want the better performance of correctly hardened and tempered carbon steel, Draper, Tough-Tools and Stanley still sell them.