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Many households have at least a few different types of screwdrivers lying around for various purposes, but those tools hanging around in a junk drawer may not be the best choice for the job you need to complete. It is important to choose the correct screwdriver size, as well as the correct driver type, to ensure you do not damage the screw while it is turning. If the head of the screw becomes damaged, it may be difficult or impossible to either drive or remove the screw. Choosing the correct screwdriver size starts with examining the head of the screw itself.
Before you apply force to a screw with the screwdriver, place the head of the tool against the screw to test for fit. With Phillips screwdrivers, if there is play between the head of the tool and the screw head, the screwdriver size may be too small. If the screwdriver does snugly into the screw head snugly, the screwdriver size may be too large. The best size of screwdriver for the job will be the one that fits snugly into the screw head without wobbling, and without unseating at the slightest turn. It is usually best to have a few different sizes of screwdriver on hand to ensure the proper fit.
Flathead, or blade, screwdrivers will fit differently into the head of the screw. The same criteria apply to this screwdriver selection: if the blade does not fit into the slot on the head of the screw, the driver is too large, and if it wobbles around, the screwdriver size is too small. There is, however, one other consideration when using a flathead screwdriver: the width of the blade. The driver head may fit snugly into the slot on the screw head, but if the head of the driver is not wide enough, it may not be able to turn the screw without damaging it.
The length of the screwdriver will also have an impact on its usefulness for a particular job. Very short screwdrivers, sometimes known as stubby drivers, are useful for turning screws in tight spots, whereas exceptionally long drivers will be useful for accessing screws in hard to reach places. Long drivers are often used in engine compartments on automobiles, for example. The length will have an impact on how much torque can be applied to the screw, as well as how much control the user will have during the turning process. Whenever possible, choose a driver that is a moderate length; only use very short or very long drivers if the job cannot be performed otherwise.