Bit Sockets & Bits

Determine the right drive

Bits have a hexagon shank that fits into a holder or machine. The most common size is 6.3 mm, also known as 1/4 inch. Smaller sizes, like 4 mm, are used less often. Larger sizes, such as 12.9 mm (1/2 inch), are for heavy-duty tools. Always check the drive of your bit holder or impact driver. A wrong drive causes play and damages the bit. For a complete set with sockets and bits, look at bit socket sets.

Choose the profile and profile size

The profile determines how the bit grips the screw head. The most common are Phillips, Pozidriv, Torx and hex. Phillips is for cross-head screws, Pozidriv has extra ribs and is often used in furniture. Torx is a star shape that gives lots of grip and less wear. Always use the correct size, such as PH2 or T20. A wrong size causes slipping and rounding of the screw head. A bit set with different profiles and sizes prevents you from having to search for a single bit.

Determine the required length

The length of a bit determines its reach. Short bits of 25 mm are handy in tight spaces. They give less leverage and are more stable when driving straight. Long bits of 50 mm or more reach recessed screws. There are also bit holders and adapters that extend the reach. Consider the space around the screw. In an engine bay, a screw is sometimes deeply recessed, then a longer bit is necessary. For a specific size you are missing, order a single bit in the right version.

Mind material and finish

For normal screwdriving, use standard bits of chrome-vanadium steel. For impact tools, such as an impact wrench, you need specially hardened bits. These are often black and have a reinforced shank. A magnetic tip holds small screws and prevents drops. A surface treatment against corrosion extends service life. Choose the finish that suits your working conditions. Rough environments call for a robust coating.