Understanding Metric Screw Drive Sizes: A Comprehensive Guide

Screw drive sizes are an important consideration when selecting the right screwdriver for a particular screw head. The size of a screw drive is typically designated by a number, such as Phillips #00, or through a code system that indicates the increasing size of the drive. The most common flat-head or slotted screwdriver sizes are 3.5mm, 5.5mm, and 6.5mm, which are used for precision work, general purposes, and larger screws, respectively. Phillips-head screwdrivers, on the other hand, often use a combination of letters and numbers to indicate size, such as PH0000 for the smallest size. It's worth noting that the numerical codes for Phillips drives may not directly correspond to the nominal screw size numbers.

Flat-head/slotted screwdrivers

Slotted screwdrivers, also known as flat-head screwdrivers, are a common type of screwdriver with a wedge-shaped blade. They are often used for precision work, such as on laptops and other electronics. The measurements of a flat-head screwdriver are presented as width by length (e.g. 1/8" x 4"). The width of the tip and the length of the shank are the two most important factors when selecting a flat-head screwdriver.

The shank length determines whether the screwdriver can fit into deeper recesses or if it functions best in tight spaces. Longer shanks also have longer handles, which can be more comfortable for the user. Flat-head screwdrivers come in a variety of sizes, with common widths including 1/8", 3/16", and 5/16". These screwdrivers can be used for a variety of tasks, including automotive work and cabinetry hardware installation.

Flat-head screwdrivers can be divided into two types based on their blade profiles: keystone and cabinet. Keystone-style screwdrivers have a slightly flared blade profile that provides extra stiffness, allowing them to withstand more torque. They are commonly used for applications that require more torque or when working with larger screws. On the other hand, cabinet-style screwdrivers have a straight blade profile with no flare, allowing them to access screws in tight spaces. They are commonly used for detailed work, such as installing cabinetry hardware.

Flat-head screwdrivers are available from various brands, including Craftsman, Klein Tools, Wera, and Wiha. When purchasing a flat-head screwdriver, it is important to consider the width and length that best suit your specific needs. Additionally, the handle design and material can also be factors to consider for comfort and ease of use.

Phillips screwdrivers

The #0 Phillips head screwdriver fits screw sizes 0 and 1. It has a tip measuring 2.5 mm. This small screwdriver is used in small appliances, like coffee makers, and home electronics, such as laptops and game consoles.

The #1 Phillips driver fits screws 2, 3, and 4 and has a 3 mm tip. This small screwdriver is used in small projects, such as crafting kits or assembling jewellery boxes.

The #2 Phillips head screwdriver fits screws 5, 6, 7, 8, and 9 and has a tip measurement of 3.5 mm. This is the most common size and is often used for wood screws.

The #3 Phillips driver is used on 10, 12, 14, and 16 size screws and has a 5 mm tip. This size is commonly used in construction and building projects.

The #4 Phillips has a 6 mm tip and fits screws 18, 20, and 24.

The #5 is used on machine screws at 5/8" and 3/4" sizes and has an 8 mm tip.

Phillips head screwdrivers are also made in very small sizes, such as #0000 (1 mm tip), #000 (1.5 mm tip), and #00 (2 mm tip). These are used in precision work and are not commonly included in standard tool sets.

The Phillips screw drive was created by John P. Thompson, a resident of Portland, Oregon, who also invented the screw to go with the screwdriver. The Phillips screw was designed to prevent over-tightening, with the driver camming out before that happens. The Phillips design also self-centres and can be used with power tools, unlike the older slotted screw design.

Pozidriv screwdrivers

• Wera 05032032001 Kraftform Stainless 3355 PZ Pozidriv Screwdriver
• GEARWRENCH #1 x 3" Pozidriv Dual Material Screwdriver - 80044H
• Wera 05006164001 Kraftform Plus VDE 165i Pozidriv Insulated Screwdriver
• Wera 05017050001 Kraftform Plus 918 SPZ Pozidriv Screwdriver
• Wiha 31310 SoftFinish Pozidriv Screwdriver #1 x 80mm
• Wiha 26210 Pozidriv Screwdriver with Precision Handle, 1 x 60mm

Robertson screwdrivers

The original Robertson screw was specified as ANSI Type III Square Centre. Today, the contemporary square drive screw has largely replaced the Robertson screw and is often referred to as a Robertson due to its identical drive dimensions and colour identification system. However, the contemporary square drive socket has parallel sides, rather than being tapered like the original Robertson design.

There are currently five different Robertson screwdriver types available, with suitable screw sizes indicated by colour:

• Orange drivers (#00) are used with screw types 1 and 2 and have a recess size range of 1.77-1.80 mm.
• Yellow drivers (#0) are used with screw types 3 and 4 and have a recess size range of 2.29 to 2.31 mm.
• Green Robertson screwdrivers (#1) are used with screw types 5, 6, and 7, with a recess size range of 2.82 to 2.86 mm.
• Red Robertson screwdrivers are used with screw types 8, 9, and 10 and have a recess size range of 3.34 to 3.38 mm.
• Black Robertson drivers are used with the largest screws, types 12 and higher, and have a recess range of 4.81 to 4.85 mm.

Torx screwdrivers

The Wheeler 55-Piece SAE/Metric Hex and Torx Screwdriver Set is a comprehensive kit that includes all the most common bits for your screwdriving needs. The set features a range of Torx bits in various sizes, including T1, T2, T3, T4, TT5, TT6, TT7, TT8, TT9, TT10, TT15, TT20, TT25, TT30, TT35, TT40, TT45, and TT50. With such a wide range of Torx sizes, this set is suitable for a variety of applications, from gun maintenance to electronics repair.

The Torx bits in the Wheeler set are designed to fit securely into your screwdriver handle, ensuring a tight grip for efficient torque transfer. The set includes two handles: a 1/4" driver handle and a 4mm driver handle. This variety allows you to choose the right handle for the job, providing versatility and comfort during use.

The Wheeler 55-piece set also includes SAE Hex and metric Hex bits, giving you even more options for different screw head types. The SAE Hex bits range from .028" to 5/16", while the metric Hex bits range from 0.7mm to 10mm, covering all the standard metric sizes.

All the bits in the Wheeler set are neatly organised in a durable plastic case, making it easy to find the right bit for the job and keeping your workspace tidy. The case also makes it convenient to store and transport your screwdriver set, ensuring that you always have the right tools with you wherever your projects take you.

Frequently asked questions