TAP DRILL SIZE CALCULATOR

• Cutting Taps UNC, UNF, M, and MF

   Tap Drill Size

   Tap Drill Size = Basic Major Diameter – Pitch


• Cutting Taps UNC and UNF

   Drilled Hole Size in Inches

   Requirements

   Basic Major Diameter

   Desired Percentage of Thread*

   Threads per Inch

• Cutting Taps UNC and UNF

   Basic Major Diameter – 0.01299 x Desired Percentage of Thread*/Threads per Inch


• Cutting Taps M and MF

   Drill Hole Size in mm 

   Requirements 

   Basic Major Diameter 

   Desired Percentage of Thread*

   Pitch


• Formula

   Basic Major Diameter – Pitch x Desired Percentage of Thread*/76.98

   *The actual percentage of thread will vary due to the runout of the drilling operation.
Cutting Taps (inches)


Basic Major Diameter (metric): -(0.0068 x Percent of full thread) / Number of Thread per Inch Drilled Hole Size (inches)
= 
            
Cutting Taps (metric)


Basic Major Diameter(metric): -(Percent of thread) x Pitch Drilled Hole Size (metric)
=   
           

• Forming Taps UNC, UNF, M, and MF

   Tap Drill Size

   Tap Drill Size = Basic Major Diameter – Pitch/2


• Forming Taps UNC and UNF

   Drilled Hole Size in Inches

   Requirements

   Basic Major Diameter

   Desired Percentage of Thread*

   Threads per Inch


• Formula

   Basic Major Diameter – 0.0068 x Desired Percentage of Thread*/Threads per Inch


• Forming Taps M and MF

   Drill Hole Size in mm

   Requirements

   Basic Major Diameter

   Desired Percentage of Thread*

   Pitch


• Formula

   Basic Major Diameter – Pitch (mm) x Desired Percentage of Thread*/147.06

   *The actual percentage of thread will vary due to the runout of the drilling operation.
Forming Taps (inches)




Basic Major Diameter: -(0.01299 x Percent of full thread) / Number of thread per inch Drilled Hole Size (inches)
=
             
Forming Taps (metric)


Basic Major Diameter (metric): -(Percent of thread pitch in mm) Drilled Hole Size (metric)
=