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Drill / Tap Chart |
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Don't have a drill/tap chart handy?
If you want to drill the proper hole for tapping, just
remember this simple formula,
Drill Size =
Diameter - Pitch. Lets say you need to
dill and tap for a 1/2"-13 bolt.
Diameter - Pitch
1/2" = .500
13 TPI = 1 ÷ 13 ( to convert TPI to a fraction) =
.0769 = roundup to .077
So, .500 (dia.) - .077(pitch) = .423
Convert .423 to a fraction
.423 x whatever denominator you want to get closest to.
You can use 8ths, 16ths, 32nds, 64ths, etc.
e.g. = .423 x 64 = 27.072 which equals 27/64"
Drill a 27/64" hole for a 1/2"
tapped hole.
Need metric? No prob! Just remember
Diameter - Pitch
Let's say it's a 6mm x 1mm bolt
6 - 1 = 5
Drill a 5mm hole for a 6mm tapped
hole. Don't have a metric bit? Nobody does.
Simply convert to standard.
5 ÷ 25.4 (mm in one inch) = .197
.197 x 64 = 12.608 = 13/64"
If all else fails, just print out the charts below and
keep 'em in your toolbox! |
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American Standard
Threads |
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Metric Threads |
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Thread
Size |
Pitch |
Drill |
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Thread
Size |
Pitch |
Drill |
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Tap
Size |
Drill |
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Center |
Size |
Dec. |
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Center |
Size |
Dec. |
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Std |
Dec. |
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0-80 |
NF |
3/64 |
0.047 |
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9/16-12 |
NC |
31/64 |
0.484 |
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2.5 -.45 |
5/64 |
.0781 |
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1-64 |
NC |
53 |
0.06 |
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18 |
NF |
33/64 |
0.516 |
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2.6 -.45 |
# 45 |
.082 |
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72 |
NF |
53 |
0.06 |
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5/8-11 |
NC |
17/32 |
0.531 |
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3-.50 |
# 39 |
.0995 |
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2-56 |
NC |
50 |
0.07 |
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18 |
NF |
37/64 |
0.578 |
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.60 |
3/32 |
.0937 |
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64 |
NF |
50 |
0.07 |
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3/4-10 |
NC |
21/32 |
0.656 |
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.75 |
# 43 |
.089 |
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3-48 |
NC |
47 |
0.079 |
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16 |
NF |
11/16 |
0.688 |
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3.5 -.60 |
# 33 |
.113 |
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56 |
NF |
45 |
0.082 |
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7/8-9 |
NC |
49/64 |
0.766 |
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4-.70 |
# 30 |
.1285 |
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4-40 |
NC |
43 |
0.089 |
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14 |
NF |
13/16 |
0.813 |
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.75 |
1/8 |
.125 |
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48 |
NF |
42 |
0.094 |
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1-8 |
NC |
7/8 |
0.875 |
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4.5 -.75 |
# 26 |
.147 |
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5-40 |
NC |
38 |
0.102 |
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14 |
NS |
15/16 |
0.938 |
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5 -.75 |
# 19 |
.166 |
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44 |
NF |
37 |
0.104 |
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1 1/8-7 |
NC |
63/64 |
0.984 |
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.80 |
# 19 |
.166 |
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6-32 |
NC |
36 |
0.107 |
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12 |
NF |
1 3/64 |
1.047 |
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.90 |
# 20 |
.161 |
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40 |
NF |
33 |
0.113 |
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1 1/4-7 |
NC |
1 7/64 |
1.109 |
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1.00 |
5/32 |
.156 |
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8-32 |
NC |
29 |
0.136 |
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12 |
NF |
1 11/64 |
1.172 |
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5.5 -.75 |
3/16 |
.1875 |
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36 |
NF |
29 |
0.136 |
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1 3/8-6 |
NC |
1 7/32 |
1.219 |
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.90 |
# 14 |
.182 |
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10-24 |
NC |
25 |
0.15 |
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12 |
NF |
1 19/64 |
1.297 |
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6 -1.00 |
# 9 |
.196 |
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32 |
NF |
21 |
0.159 |
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1 1/2-6 |
NC |
1 11/32 |
1.344 |
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1.25 |
3/16 |
.1875 |
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12-24 |
NC |
16 |
0.177 |
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12 |
NF |
1 27/64 |
1.422 |
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7 -1.00 |
15/64 |
.234 |
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28 |
NF |
14 |
0.182 |
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1 3/4-5 |
NC |
1 9/16 |
1.563 |
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1.25 |
# 1 |
.228 |
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1/4-20 |
NC |
7 |
0.201 |
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2-4 1/2 |
NC |
1 25/32 |
1.781 |
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8 -1.00 |
J |
.277 |
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28 |
NF |
3 |
0.213 |
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2 1/4-4 1/2 |
NC |
2 1/32 |
2.031 |
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1.25 |
17/64 |
.265 |
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5/16-18 |
NC |
F |
0.257 |
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2 1/2-4 |
NC |
2 1/4 |
2.25 |
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9 -1.00 |
5/16 |
.3125 |
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24 |
NF |
I |
0.272 |
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2 3/4-4 |
NC |
2 1/2 |
2.5 |
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1.25 |
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.3125 |
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3/8-16 |
NC |
5/16 |
0.313 |
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3-4 |
NC |
2 3/4 |
2.75 |
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10 -1.00 |
23/64 |
.359 |
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24 |
NF |
Q |
0.332 |
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3 1/4-4 |
NC |
3 |
3 |
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1.25 |
11/32 |
.3437 |
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7/16-14 |
NC |
U |
0.368 |
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3 1/2-4 |
NC |
3 1/4 |
3.25 |
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1.50 |
R |
.339 |
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20 |
NF |
25/64 |
0.391 |
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3 3/4-4 |
NC |
3 1/2 |
3.5 |
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11 -1.50 |
3/8 |
.375 |
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1/2-13 |
NC |
27/64 |
0.422 |
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4-4 |
NC |
3 3/4 |
3.75 |
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12 -1.25 |
7/16 |
.4375 |
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20 |
NF |
29/64 |
0.453 |
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1.50 |
13/32 |
.406 |
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1.75 |
13/32 |
.406 |
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Taper Pipe |
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Straight Pipe |
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13 -1.50 |
29/64 |
.453 |
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1.75 |
29/64 |
.453 |
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Thread |
Drill |
Thread |
Drill |
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Thread |
Drill |
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2.00 |
7/16 |
.4375 |
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1/16 |
D |
1 1/2 |
1 47/64 |
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1/16 |
1/4 |
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14 -1.25 |
33/64 |
.5156 |
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1/8 |
R |
2 |
2 7/32 |
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1/8 |
11/32 |
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1.75 |
1/2 |
.500 |
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1/4 |
7/16 |
2 1/5 |
2 5/8 |
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1/4 |
7/16 |
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2.00 |
15/32 |
.4687 |
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3/8 |
37/64 |
3 |
3 1/4 |
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3/8 |
37/64 |
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15 -1.75 |
17/32 |
.531 |
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1/2 |
45/64 |
3 1/2 |
3 3/4 |
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1/2 |
23/32 |
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2.00 |
33/64 |
.5156 |
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3/4 |
59/64 |
4 |
4 1/4 |
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3/4 |
59/64 |
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16 -2.00 |
35/64 |
.5468 |
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1 |
1 5/32 |
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1 |
1 5/32 |
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17 -.200 |
19/32 |
.5937 |
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1 1/4 |
1 1/2 |
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1 1/4 |
1 1/2 |
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18 -1.50 |
21/32 |
.656 |
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1 1/2 |
1 3/4 |
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2 |
2 7/32 |
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2 1/2 |
2 21/32 |
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