A Simple Guide to Flat Head Screwdriver Sizes

While it is one of the most basic tools ever designed, a flat head screwdriver nonetheless comes in a variety of sizes and lengths, each meant to serve a particular purpose. Its name is a little misleading, for a flat head screwdriver often serves equally well as a miniature pry bar, a scraper and a chisel. To get the most effective use out of a flat head screwdriver for any given task, it is best to choose a size of screwdriver that is suitable. This guide to flat head screwdriver sizes will outline for you everything you need to know about the different types available to you. Each size uses the same basic design, but the differences lie in the length of the shaft and the width and thickness of the driver itself.

Slotted Screwdrivers

Another way to describe a flat head screwdriver is to call it a slotted screwdriver. This stems from the fact that the flat head of the driver is meant to fit snugly into the slot of a screw, tightening or loosening it. A slotted screw is distinguished from the equally-common Phillips head screw and somewhat less common square head screw. There is hex screws that require a six-sided driver known as a hex wrench or Allen wrench. Slotted screwdrivers work best when they fit appropriately into the slot of the screw. A screw with a head that is ¼ inch wide is not easily turned by a flat head driver that is only half as wide. Likewise, the thickness of the slot on the screw head should also be matched by the thickness of the screwdriver for best results. 

Flathead Screwdriver Sizes

Flathead screwdrivers range in size from mere millimeters up to bigger fractions of an inch. Two measurements are noted for each screwdriver: the length of the shaft and the width of the driver head. Examples of flat head screwdriver sizes in inches include 3/32 by 1½, 3/16 by 1½, 1/8 by 4, 3/16 by 4 and ¼ by 4. The first number represents the width of the driver head, while the second size indicates the shaft length. The longer the shaft, the farther the screwdriver can reach. This is especially handy when doing automotive work, as screws are often placed far back in an engine block. If you can reach the head of a screw without the aid of a long shaft, it is better to use a screwdriver with a smaller shaft. Stubby flat head screwdrivers have shafts of 1½. They are useful for close-up work. The downside to this type of screwdriver is that the handle is very stubby too. Screwdrivers with longer shafts have proportionately longer handles. This enables you to get a better grip on the screwdriver as you use it. 

Flathead Screwdriver Sets

Flathead screwdrivers are sold individually, but the best way to cover all of your bases when driving and removing screws is to have a set. A screwdriver set can consist of just flat head screwdrivers or a combination of flat head and Phillips head varieties. In a set, you will get a good selection of flat head screwdrivers including at least one with a short shaft, one with a long shaft and several in between. 

Standard flat head screwdrivers are measured in inches and fractions of inches. However, having a set of miniature flat head screwdrivers measured in millimeters is handy for very small screws such as those found on glasses, watches and small electrical components.