TAP CHART - FORM THREADS
Calculating Tap Drill Sizes - Thread Forming Taps
Drill Size = Major Diameter - [(0.0068 X desired % of thread) / Threads per inch]
Drill Size (mm) = Major Diameter - [(0.0068 X desired % of thread) x Pitch (mm)]
Thread forming taps require a larger pre-tap hole size than a cutting tap. Too small of a pre-tap hole size may result in excessive tap wear, torque, and possible tap breakage.
*These calculations are based upon theoretical values and are only intended for planning purposes. Actual results will vary. No responsibility from SMT is assumed.
|
TAP SIZE |
TPI |
75% THREAD |
65% THREAD |
DRILL SIZE |
|
0 |
80 |
0.054 |
0.055 |
#54 / 1.4mm |
|
1 |
64 |
0.066 |
0.067 |
#51 / 1.7mm |
|
1 |
72 |
0.067 |
0.068 |
#51 / 1.75mm |
|
2 |
56 |
0.078 |
0.079 |
#47 / 2.0mm |
|
2 |
64 |
0.079 |
0.080 |
2.0mm |
|
3 |
48 |
0.090 |
0.091 |
#43 / 2.3mm |
|
3 |
56 |
0.091 |
0.092 |
2.3mm |
|
4 |
40 |
0.100 |
0.101 |
#39 |
|
4 |
48 |
0.103 |
0.104 |
#37 / 2.6mm |
|
5 |
40 |
0.113 |
0.114 |
#33 / 2.9mm |
|
5 |
44 |
0.114 |
0.115 |
#33 / 2.9mm |
|
6 |
32 |
0.124 |
0.125 |
3.1mm |
|
6 |
40 |
0.126 |
0.127 |
1/8” / 3.2mm |
|
8 |
32 |
0.149 |
0.150 |
#25 / 3.8mm |
|
8 |
36 |
0.151 |
0.152 |
#24 |
|
10 |
24 |
0.170 |
0.172 |
11/64” /4.3mm |
|
10 |
32 |
0.175 |
0.176 |
#16 / .176” / 4.4mm |
|
12 |
24 |
0.196 |
0.198 |
#9 / 5.0mm |
|
12 |
28 |
0.199 |
0.201 |
#7 / 5.1 mm |
|
1/4 |
20 |
0.225 |
0.227 |
5.75mm |
|
1/4 |
28 |
0.233 |
0.235 |
“A” / 5.9mm |
|
5/16 |
18 |
0.285 |
0.287 |
7.25mm |
|
5/16 |
24 |
0.292 |
0.294 |
.293” / 7.4mm |
|
3/8 |
16 |
0.344 |
0.347 |
“S” / 11/32” |
|
3/8 |
24 |
0.355 |
0.357 |
9.0mm |
|
7/16 |
14 |
0.402 |
0.405 |
“Y” |
|
7/16 |
20 |
0.414 |
0.416 |
“Z” / 25/64" |
|
1/2 |
13 |
0.462 |
0.466 |
15/32” / .463” |
|
1/2 |
20 |
0.475 |
0.478 |
29/64” / 12mm |
|
9/16 |
12 |
0.520 |
0.526 |
31/64” |
|
9/16 |
18 |
0.534 |
0.538 |
33/64” |
|
5/8 |
11 |
0.579 |
0.585 |
17/32” |
|
5/8 |
18 |
0.597 |
0.600 |
37/64” |
|
3/4 |
10 |
0.699 |
0.706 |
45/64” |
|
3/4 |
16 |
0.718 |
0.722 |
23/32” |
|
7/8 |
9 |
0.818 |
0.826 |
49/64” |
|
7/8 |
14 |
0.839 |
0.843 |
13/16” |
|
1 |
8 |
0.936 |
0.945 |
7/8” |
|
1 |
12 |
0.958 |
0.963 |
59/64” |
METRIC
|
TAP SIZE |
PITCH |
75% THREAD |
65% THREAD |
DRILL SIZE |
|
M1.6 |
0.35 |
0.057 |
0.058 |
1.45mm |
|
M1.7 |
0.35 |
0.061 |
0.062 |
1.55mm |
|
M2 |
0.4 |
0.072 |
0.073 |
1.85mm |
|
M2.5 |
0.45 |
0.091 |
0.092 |
2.3mm |
|
M3 |
0.5 |
0.110 |
0.111 |
#35 |
|
M3.5 |
0.6 |
0.128 |
0.129 |
#30 |
|
M4 |
0.7 |
0.145 |
0.146 |
3.70mm |
|
M5 |
0.8 |
0.183 |
0.184 |
#14 |
|
M6 |
1 |
0.218 |
0.220 |
5.50mm |
|
M8 |
1.25 |
0.291 |
0.294 |
7.40mm |
|
M10 |
1.5 |
0.365 |
0.368 |
9.30mm |
|
M12 |
1.75 |
0.439 |
0.442 |
7/16” |
Tap drill size calculator. Calculate the proper drill size for cutting or forming taps in both inch and metric systems. Enter the hole size, tap threads per inch, and desired thread height percentage, to provide the recommended drill size.