Tap Drill worksheet

1. Nearest standard drill diameter: 1.3 mm

1. M1.6 × 0.35: the outside diameter (D) and the distance between threads (P)

   $\mathrm{D,\; P}$$=1.6\text{\hspace{0.17em}mm}\text{,}0.35\text{\hspace{0.17em}mm}$

2. Work out how much the threads cut into the diameter for 65% thread: 0.01299 × % × pitch

   $0.01299\times 65\times 0.35$$=0.2955225\text{\hspace{0.17em}mm}$

3. Take that off the outside diameter to get the exact drill size

   $1.6-0.2955225$$=1.3044775\text{\hspace{0.17em}mm}$

4. Pick the nearest drill you can actually buy: 1.3 mm

   $\text{1.3 mm}$$=1.3\text{\hspace{0.17em}mm}$

5. Run the formula backward to see how much thread that drill really leaves

   $\frac{1.6-1.3}{0.01299\times 0.35}$$=\mathrm{65.98\%}$

2. Nearest standard drill diameter: 6.4 mm

1. M8 × 1.75: the outside diameter (D) and the distance between threads (P)

   $\mathrm{D,\; P}$$=8\text{\hspace{0.17em}mm}\text{,}1.75\text{\hspace{0.17em}mm}$

2. Work out how much the threads cut into the diameter for 70% thread: 0.01299 × % × pitch

   $0.01299\times 70\times 1.75$$=1.591275\text{\hspace{0.17em}mm}$

3. Take that off the outside diameter to get the exact drill size

   $8-1.591275$$=6.408725\text{\hspace{0.17em}mm}$

4. Pick the nearest drill you can actually buy: 6.4 mm

   $\text{6.4 mm}$$=6.4\text{\hspace{0.17em}mm}$

5. Run the formula backward to see how much thread that drill really leaves

   $\frac{8-6.4}{0.01299\times 1.75}$$=\mathrm{70.38\%}$

3. Nearest standard drill diameter: 0.4531 in

1. 0.5-12: the pitch is one inch divided by the threads per inch

   $\frac{1}{12}$$=0.08333333\text{\hspace{0.17em}in}$

2. Work out how much the threads cut into the diameter for 50% thread: 0.01299 × % × pitch

   $0.01299\times 50\times 0.08333333$$=0.054125\text{\hspace{0.17em}in}$

3. Take that off the outside diameter to get the exact drill size

   $0.5-0.054125$$=0.445875\text{\hspace{0.17em}in}$

4. Pick the nearest drill you can actually buy: 29/64"

   $\text{29/64"}$$=0.4531\text{\hspace{0.17em}in}$

5. Run the formula backward to see how much thread that drill really leaves

   $\frac{0.5-0.4531}{0.01299\times 0.08333333}$$=\mathrm{43.3\%}$

4. Nearest standard drill diameter: 0.1094 in

1. #5-40 UNC: the pitch is one inch divided by the threads per inch

   $\frac{1}{40}$$=0.025\text{\hspace{0.17em}in}$

2. Work out how much the threads cut into the diameter for 50% thread: 0.01299 × % × pitch

   $0.01299\times 50\times 0.025$$=0.0162375\text{\hspace{0.17em}in}$

3. Take that off the outside diameter to get the exact drill size

   $0.125-0.0162375$$=0.1087625\text{\hspace{0.17em}in}$

4. Pick the nearest drill you can actually buy: 7/64"

   $\text{7/64"}$$=0.1094\text{\hspace{0.17em}in}$

5. Run the formula backward to see how much thread that drill really leaves

   $\frac{0.125-0.1094}{0.01299\times 0.025}$$=\mathrm{48.11\%}$

5. Nearest standard drill diameter: 0.0625 in

1. #1-72 UNF: the pitch is one inch divided by the threads per inch

   $\frac{1}{72}$$=0.01388889\text{\hspace{0.17em}in}$

2. Work out how much the threads cut into the diameter for 60% thread: 0.01299 × % × pitch

   $0.01299\times 60\times 0.01388889$$=0.010825\text{\hspace{0.17em}in}$

3. Take that off the outside diameter to get the exact drill size

   $0.073-0.010825$$=0.062175\text{\hspace{0.17em}in}$

4. Pick the nearest drill you can actually buy: 1/16"

   $\text{1/16"}$$=0.0625\text{\hspace{0.17em}in}$

5. Run the formula backward to see how much thread that drill really leaves

   $\frac{0.073-0.0625}{0.01299\times 0.01388889}$$=\mathrm{58.2\%}$

6. Nearest standard drill diameter: 5.3 mm

1. M6 × 1: the outside diameter (D) and the distance between threads (P)

   $\mathrm{D,\; P}$$=6\text{\hspace{0.17em}mm}\text{,}1\text{\hspace{0.17em}mm}$

2. Work out how much the threads cut into the diameter for 55% thread: 0.01299 × % × pitch

   $0.01299\times 55\times 1$$=0.71445\text{\hspace{0.17em}mm}$

3. Take that off the outside diameter to get the exact drill size

   $6-0.71445$$=5.28555\text{\hspace{0.17em}mm}$

4. Pick the nearest drill you can actually buy: 5.3 mm

   $\text{5.3 mm}$$=5.3\text{\hspace{0.17em}mm}$

5. Run the formula backward to see how much thread that drill really leaves

   $\frac{6-5.3}{0.01299\times 1}$$=\mathrm{53.89\%}$

7. Nearest standard drill diameter: 0.18 in

1. #12-24 UNC: the pitch is one inch divided by the threads per inch

   $\frac{1}{24}$$=0.04166667\text{\hspace{0.17em}in}$

2. Work out how much the threads cut into the diameter for 65% thread: 0.01299 × % × pitch

   $0.01299\times 65\times 0.04166667$$=0.03518125\text{\hspace{0.17em}in}$

3. Take that off the outside diameter to get the exact drill size

   $0.216-0.03518125$$=0.18081875\text{\hspace{0.17em}in}$

4. Pick the nearest drill you can actually buy: #15

   $\text{\#15}$$=0.18\text{\hspace{0.17em}in}$

5. Run the formula backward to see how much thread that drill really leaves

   $\frac{0.216-0.18}{0.01299\times 0.04166667}$$=\mathrm{66.51\%}$

8. Nearest standard drill diameter: 10.6 mm

1. M12 × 1.5 (fine): the outside diameter (D) and the distance between threads (P)

   $\mathrm{D,\; P}$$=12\text{\hspace{0.17em}mm}\text{,}1.5\text{\hspace{0.17em}mm}$

2. Work out how much the threads cut into the diameter for 70% thread: 0.01299 × % × pitch

   $0.01299\times 70\times 1.5$$=1.36395\text{\hspace{0.17em}mm}$

3. Take that off the outside diameter to get the exact drill size

   $12-1.36395$$=10.63605\text{\hspace{0.17em}mm}$

4. Pick the nearest drill you can actually buy: 10.6 mm

   $\text{10.6 mm}$$=10.6\text{\hspace{0.17em}mm}$

5. Run the formula backward to see how much thread that drill really leaves

   $\frac{12-10.6}{0.01299\times 1.5}$$=\mathrm{71.85\%}$

9. Nearest standard drill diameter: 0.4688 in

1. 1/2-20 UNF: the pitch is one inch divided by the threads per inch

   $\frac{1}{20}$$=0.05\text{\hspace{0.17em}in}$

2. Work out how much the threads cut into the diameter for 60% thread: 0.01299 × % × pitch

   $0.01299\times 60\times 0.05$$=0.03897\text{\hspace{0.17em}in}$

3. Take that off the outside diameter to get the exact drill size

   $0.5-0.03897$$=0.46103\text{\hspace{0.17em}in}$

4. Pick the nearest drill you can actually buy: 15/32"

   $\text{15/32"}$$=0.4688\text{\hspace{0.17em}in}$

5. Run the formula backward to see how much thread that drill really leaves

   $\frac{0.5-0.4688}{0.01299\times 0.05}$$=\mathrm{48.11\%}$

10. Nearest standard drill diameter: 6.9 mm

1. M8 × 1.75: the outside diameter (D) and the distance between threads (P)

   $\mathrm{D,\; P}$$=8\text{\hspace{0.17em}mm}\text{,}1.75\text{\hspace{0.17em}mm}$

2. Work out how much the threads cut into the diameter for 50% thread: 0.01299 × % × pitch

   $0.01299\times 50\times 1.75$$=1.136625\text{\hspace{0.17em}mm}$

3. Take that off the outside diameter to get the exact drill size

   $8-1.136625$$=6.863375\text{\hspace{0.17em}mm}$

4. Pick the nearest drill you can actually buy: 6.9 mm

   $\text{6.9 mm}$$=6.9\text{\hspace{0.17em}mm}$

5. Run the formula backward to see how much thread that drill really leaves

   $\frac{8-6.9}{0.01299\times 1.75}$$=\mathrm{48.39\%}$