Drill Bit Size Chart (Metric-Imperial Equivalents)

This drill bit size chart primarily serves as a reference guide to help you select the correct drill bit size for a specific task. It provides a correlation between various measurement systems and the corresponding drill bit sizes. This ensures that the right bit is chosen for a particular application, preventing damage to the workpiece and the drill bit itself, specifically for:

• Matching drill bit size to screw or bolt size: It helps determine the appropriate drill bit diameter for creating pilot holes for screws or bolts.
• Converting between measurement systems: It facilitates conversions between metric and imperial units for drill bit sizes.

We trust that the information below is self-explanatory and straightforward.

Gauge sizing is directly related to drill bit size, and it affects your selection due to these factors:

• Precision: Gauge sizing, especially in the letter/number system, offers a high degree of precision for smaller drill bits. This is crucial for applications requiring exact hole dimensions.
• Compatibility: Many fasteners and components are specified by their gauge size. To ensure a proper fit, the drill bit must match the gauge size of the intended component.
• Standardisation: Gauge sizing provides a standardised method for specifying drill bit dimensions, facilitating communication and compatibility across different industries.

In essence, gauge sizing is a way to define the diameter of a drill bit, allowing for accurate selection and use in various applications.

Considerations:

• The choice of drill size and thread depth can vary significantly based on the material being tapped (eg steel, aluminium, plastic).
• The desired thread depth affects the necessary clearance for the tap.
• The tightness of the thread (close, medium, or free fit) influences the drill size.
• Different tap types (taper, plug, bottoming) require slightly different drill sizes.
• The Engineers Black Book’s section in calculation of tapping drill sizes advises to “use a good cutting oil or lubricant rather than coolant for fluteless (thread forming) taps”.

Notes:

• This table covers a range of sizes but might not include all available drill bit sizes.
• Not all metric drill bits have imperial equivalents, and vice versa.
• Some metric values are close enough to essentially have the same imperial counterpart.
• Some values are rounded to their nearest thousandth millimeters and ten-thousandth decimal inches.

Important:

• Always consult a detailed drill bit chart for accurate and precise drill size selection.

You may want to consider getting the Engineers Black Book (3^rd Edition – Metric) for more complete information, specifically:

• Metric (millimetres), decimal and fractional inches, gauge sizes and thread sizes from 0.100 mm up to 101.600 mm (4 inches)

More size charts

• Anchor Bolt Size Chart: Sort through a wide variety of metric anchor bolt types: countersunk head sleeve anchor, drop-in anchor, hex flange nut sleeve anchor, flush head sleeve anchor and stud anchor. Common metric diameters listed.
• Fastener Reference Chart: Cross-reference the measurement of your bolt, nut or screw with these comprehensive table of sizes. Metric, Unified Thread Standard and British Thread Standards values matched. There are also simplified illustrations of how to identify metric or imperial fasteners by thread pitch and threads per inch, respectively.
• Loctite Application Chart: Know which Loctite product to use with various materials and surfaces, from bricks and ceramics to vinyl and wood.
• Pulley Size Chart: Sort through a wide variety of aluminium and cast-iron pulleys for different belt sections and grooves. For taper locks, pilot bores and bores with keyway. Metric and imperial sizes available.
• Socket Sizing Cross-Reference Chart (Metric-Imperial Values): Match the right (or nearest alternative) sockets and drives. Metric and imperial sizes available.
• Spanner Size Chart: Find out which spanner size to use for your bolt, nut or screw with a hexagonal head. Metric and imperial (UNC/UNF) sizes matched.
• Tapping Drill Size Chart for Thread Cutting Taps: Find the appropriate (and nearest alternative) drill size for creating a pilot hole before cutting threads in a workpiece. Common coarse and fine drill sizes listed. Metric and imperial (US decimal / fractional inches) values matched.

AIMS' Note on Safe Use of Power Tools

• Inspection: Before using any tool, carefully inspect it for cracks, chips, loose handles, worn / mushroomed heads or any other signs of damage. Damaged or defective tools may cause harm! Ensure all guards are in place.
• Right tool for the job: Make sure you understand the intended purpose of each tool and choose the correct one for your specific job. Don't try to make a screwdriver work as a pry bar or a wrench as a hammer.
• Safe handling: Carry sharp tools pointed down and away from your body. Never carry tools in your pockets where they can cause injury. When passing a tool to someone, extend the handle first.
• PPE: Wear safety glasses or goggles to protect your eyes from flying debris. Consider gloves depending on the tool and task to prevent cuts or blisters but without compromising comfort, dexterity and protection. If working with noisy tools, wear ear protection.
• Maintenance: Keep your tools clean, sharp and properly maintained. Store them in a safe and organised place when not in use.
• During use: Maintain a firm grip and good balance while using the tool. Avoid distractions and focus on the task. Don't force the tool; let it work at its own pace. Keep cords clear of the cutting path and away from heat or sharp objects. Never leave a running tool unattended. When finished, turn the tool off, unplug it, and wait for any moving parts to stop completely before cleaning or making adjustments.