5/8-11 Tap Drill Bit Size is a 17/32" Size

5/8-11 Tap Drill Size

The correct tap drill size for a 5/8-11 UNC thread is 17/32. This drill size is equal to 0.5312" in decimal and 13.49 mm in metric. For shops, maintenance teams, and production environments, this provides a reliable starting point when preparing holes for standard 5/8-11 internal threads.

Drill Size for a 5/8-11 Tap

When selecting a drill bit for a 5/8-11 tap, the goal is to create a hole that supports proper thread engagement without making tapping unnecessarily difficult. A 17/32 drill is commonly used because it balances material removal with enough remaining stock for the tap to form clean UNC threads. This helps improve tool control and supports more consistent results across manual and machine tapping applications.

Hole Size for 5/8-11 Tap (UNC)

The starting hole size directly affects how the finished 5/8-11 thread forms. If the hole is too small, tapping torque increases and the risk of broken taps rises. If the hole is too large, thread percentage may be reduced beyond what the application requires. Using a 17/32 drill for this UNC thread size gives machinists a practical hole size for general-purpose thread production in many common materials.

Why the Correct Drill Size for 5/8-11 Matters

Choosing the proper drill size for 5/8-11 threads helps support thread quality, tap life, and process efficiency. In production and repair work, the right pre-tap hole can reduce cutting load, improve chip evacuation, and lower the chance of rework. It also helps maintain dimensional consistency when parts must accept standard 5/8-11 fasteners or mating components.

Compare with a Full Tap Drill Chart

If you need to confirm related UNC, UNF, metric, or NPT drill recommendations, review our tap and drill size chart. It is a useful reference when comparing multiple thread sizes, checking nearby drill conversions, or selecting the correct bit for additional tapping operations.