Drill and Tap Chart

Tap Drill Charts by Thread Type

Select the chart that matches your application:

• Standard Tap Drill Chart (Inch Threads)
  UNC and UNF thread sizes used in general machining and fastening.
• Metric Tap Drill Chart (MM Sizes)
  Metric thread sizes with drill sizes in millimeters.
• NPT Tap Drill Chart (Pipe Threads)
  Tapered pipe threads used for sealing applications.
• Screw Tap Drill Chart
  Tap drill sizes for threaded holes used with screws and fasteners.

Complete Tap and Drill Size Chart

Use the chart below as a general reference for selecting drill sizes across multiple thread types.

Download Complete Drill Tap Chart (PDF)

How to Use a Drill and Tap Chart

A tap and drill chart is used to determine the drill size in both decimal inch and metric measurement systems.  It is also used to find the correct drill size to create the hole before cutting internal threads with a tap. Selecting the proper drill size ensures the correct percentage of thread engagement, which is critical for strength, performance, and tool life.

In most applications, tap drill sizes are selected to provide approximately 70–75% thread engagement. This offers a balance between thread strength and ease of tapping.

Tap Drill Sizes vs Pilot Holes

Tap drill sizes are used when cutting internal threads with a tap, typically in materials such as steel, aluminum, and other metals. These drill sizes are carefully selected to achieve the correct thread engagement.

Pilot holes, by contrast, are used for thread-forming screws in softer materials such as wood, plastic, or sheet metal. The key difference is that pilot holes are used for forming threads, while tap drill sizes are used for cutting threads.  This chart is not focused on thread forming applications.

Why Drill Size Matters for Thread Engagement

Using the correct drill size directly affects thread quality. A hole that is too small increases tapping torque and tool wear, while a hole that is too large reduces thread strength and holding capability.

Proper drill sizing ensures consistent results across machining, fabrication, and maintenance applications.

Tap vs. Die – Do You Need a Drill for Both?

While many users search for a “tap and die drill chart,” drill sizes are only required when using taps, not dies. Taps are used to cut internal threads and require a drilled hole before tapping. Dies are used to cut external threads on rods or bolts and do not require a drill.  Because of this, a drill and tap index applies specifically to tapping operations, even though the combined term is commonly used in search.