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Tap Drill Size Chart and Drill Decimal Equivalents
The tap drill for every inch, metric and pipe thread, how to calculate it, and a decimal chart for every fraction, number, letter and metric drill, with priced drill and tap picks.
Quick answer: On a tap drill size chart, a 1/4-20 tap takes a #7 drill (0.201 in.). For 5/16-18 use an F drill (0.257 in.), for 3/8-16 a 5/16 in. drill, for 1/2-13 a 27/64 in. drill, and for 10-24 a #25 drill. Metric is easy: subtract the pitch from the size, so M8 x 1.25 takes a 6.8 mm drill. A 1/8 NPT pipe tap takes an R or 11/32 in. drill. These sizes cut about 75% of a full thread, the standard for steel.
What size drill bit do I need for my tap?
The right drill bit for a tap is the tap drill size listed for that thread, which leaves enough metal for about 75% of a full thread. This tap drill size chart covers every common inch thread. UNC is coarse thread and UNF is fine thread.
Thread |
Tap drill |
Drill decimal (in.) |
Drill in mm |
|---|---|---|---|
#2-56 UNC |
#50 |
0.0700 |
1.78 |
#4-40 UNC |
#43 |
0.0890 |
2.26 |
#5-40 UNC |
#38 |
0.1015 |
2.58 |
#6-32 UNC |
#36 |
0.1065 |
2.71 |
#6-40 UNF |
#33 |
0.1130 |
2.87 |
#8-32 UNC |
#29 |
0.1360 |
3.45 |
#8-36 UNF |
#29 |
0.1360 |
3.45 |
#10-24 UNC |
#25 |
0.1495 |
3.80 |
#10-32 UNF |
#21 |
0.1590 |
4.04 |
#12-24 UNC |
#16 |
0.1770 |
4.50 |
#12-28 UNF |
#14 |
0.1820 |
4.62 |
1/4-20 UNC |
#7 |
0.2010 |
5.11 |
1/4-28 UNF |
#3 |
0.2130 |
5.41 |
5/16-18 UNC |
F |
0.2570 |
6.53 |
5/16-24 UNF |
I |
0.2720 |
6.91 |
3/8-16 UNC |
5/16 in. |
0.3125 |
7.94 |
3/8-24 UNF |
Q |
0.3320 |
8.43 |
7/16-14 UNC |
U |
0.3680 |
9.35 |
7/16-20 UNF |
25/64 in. |
0.3906 |
9.92 |
1/2-13 UNC |
27/64 in. |
0.4219 |
10.72 |
1/2-20 UNF |
29/64 in. |
0.4531 |
11.51 |
9/16-12 UNC |
31/64 in. |
0.4844 |
12.30 |
9/16-18 UNF |
33/64 in. |
0.5156 |
13.10 |
5/8-11 UNC |
17/32 in. |
0.5312 |
13.49 |
5/8-18 UNF |
37/64 in. |
0.5781 |
14.68 |
3/4-10 UNC |
21/32 in. |
0.6562 |
16.67 |
3/4-16 UNF |
11/16 in. |
0.6875 |
17.46 |
7/8-9 UNC |
49/64 in. |
0.7656 |
19.45 |
7/8-14 UNF |
13/16 in. |
0.8125 |
20.64 |
1-8 UNC |
7/8 in. |
0.8750 |
22.22 |
1-12 UNF |
59/64 in. |
0.9219 |
23.42 |
Number drills (#1 to #80) are also called wire gauge drills, and letter drills run from A to Z. Both fill the gaps between fractional sizes, which is why so many tap drills are a number or a letter.
Which drill and tap should I buy for common threads?
For the threads contractors and fab shops tap most, here is the exact drill, the matching tap and a combination drill tap, priced on our store. Every drill and tap below is made in the USA by Triumph Twist Drill. The combination drill taps are ITM.
Thread |
Tap drill (ThunderBit) |
Plug tap |
Combination drill tap |
|---|---|---|---|
6-32 |
#36: 012636, $1.59 each, sold in 12s (min. 24) |
071091, $7.37 each, sold in 12s |
HDT-0632, $14.83 each (min. 4) |
8-32 |
#29: 012629, $1.83 each, sold in 12s (min. 24) |
071093, $7.37 each, sold in 12s |
HDT-0832, $15.20 each (min. 4) |
10-24 |
#25: 012625, $1.92 each, sold in 12s (min. 24) |
071095, $7.37 each, sold in 12s |
HDT-1024, $15.71 each (min. 4) |
10-32 |
#21: 012621, $2.07 each, sold in 12s (min. 24) |
071096, $7.37 each, sold in 12s |
HDT-1032, $15.71 each (min. 4) |
1/4-20 |
#7: 012607, $2.86 each, sold in 12s (min. 24) |
071060, $7.08 each, sold in 6s |
HDT-1420, $18.36 each (min. 2) |
5/16-18 |
F: 012706, $3.98 each, sold in 12s |
071062, $8.27 each, sold in 6s |
HDT-5618, $25.67 each (min. 2) |
3/8-16 |
5/16 in.: 012520, $4.96 each, sold in 6s (min. 12) |
071064, $9.75 each, sold in 6s |
HDT-3816, $25.67 each (min. 2) |
1/2-13 |
27/64 in.: 012527, $9.26 each, sold in 6s |
071068, $17.70 each, sold in 3s |
HDT-1213, $36.03 each |
5/8-11 |
17/32 in.: 092834, $19.62 each (min. 2) |
071072, $34.23 each (min. 2) |
Use a drill and tap |
1/8 NPT |
11/32 in.: 012522, $6.37 each, sold in 6s |
071250, $30.98 each (min. 2) |
Use a drill and tap |
1/4 NPT |
7/16 in.: 012528, $9.82 each, sold in 6s |
071251, $34.65 each (min. 2) |
Use a drill and tap |
Store prices on Oct 2, 2026. Drill bits and taps are priced per piece and sold by the sleeve or with a small minimum, shown next to each price.
A combination drill tap drills, taps and chamfers a through hole in one pass, with a 1/4 in. hex shank for a drill or impact driver. It is fastest on sheet metal, strut, angle and thin plate. For blind holes, deep holes or hard steel, a separate drill and tap give a cleaner thread. Browse all taps and dies and combination drill taps.
How do you calculate tap drill size?
Tap drill size equals the thread's major diameter minus its pitch. For inch threads the pitch is 1 divided by the threads per inch, so a 1/4-20 tap needs 0.250 - 1/20 = 0.200 in. The nearest drill is a #7 at 0.201 in. For metric threads, subtract the pitch in millimeters: M10 x 1.5 needs 10 - 1.5 = 8.5 mm.
That rule gives about 75% thread engagement. Going past 75% adds very little strength and makes the tap much harder to turn. To check a different drill, use percent of thread = threads per inch x (major diameter - drill diameter) / 0.01299.
Drill for a 1/4-20 tap |
Decimal (in.) |
Percent of thread |
|---|---|---|
#8 |
0.1990 |
79% |
#7 |
0.2010 |
75% |
13/64 in. |
0.2031 |
72% |
#6 |
0.2040 |
71% |
#5 |
0.2055 |
69% |
So a 13/64 in. drill works in a pinch for 1/4-20 at about 72% thread. In hard or stainless steel, a slightly larger drill (lower percent) makes tapping easier and saves taps.
What is the metric tap drill size chart?
A metric tap drill is the thread size minus the pitch. This metric tap drill chart lists the coarse-pitch threads with the nearest inch drill for shops without metric bits.
Metric thread |
Tap drill |
Decimal (in.) |
Nearest inch drill |
|---|---|---|---|
M2 x 0.4 |
1.6 mm |
0.0630 |
1/16 in. (0.0625) |
M2.5 x 0.45 |
2.05 mm |
0.0807 |
#46 (0.0810) |
M3 x 0.5 |
2.5 mm |
0.0984 |
#40 (0.0980) |
M4 x 0.7 |
3.3 mm |
0.1299 |
#30 (0.1285) |
M5 x 0.8 |
4.2 mm |
0.1654 |
#19 (0.1660) |
M6 x 1.0 |
5 mm |
0.1969 |
#9 (0.1960) |
M8 x 1.25 |
6.8 mm |
0.2677 |
H (0.2660) |
M10 x 1.5 |
8.5 mm |
0.3346 |
Q (0.3320) |
M12 x 1.75 |
10.2 mm |
0.4016 |
Y (0.4040) |
M14 x 2.0 |
12 mm |
0.4724 |
15/32 in. (0.4688) |
M16 x 2.0 |
14 mm |
0.5512 |
35/64 in. (0.5469) |
M20 x 2.5 |
17.5 mm |
0.6890 |
11/16 in. (0.6875) |
M24 x 3.0 |
21 mm |
0.8268 |
53/64 in. (0.8281) |
What size drill bit for an NPT pipe tap?
An NPT pipe tap needs a larger drill than a straight tap of the same nominal size, because pipe sizes name the pipe's bore, not the thread. A 1/8 NPT tap takes an R drill (0.339 in.) or an 11/32 in. drill (0.3438 in.). The tap cuts a taper, so drill the hole straight and let the tap do the rest.
Pipe thread |
Tap drill |
Decimal (in.) |
|---|---|---|
1/16-27 NPT |
1/4 in. |
0.2500 |
1/8-27 NPT |
R or 11/32 in. |
0.3390 |
1/4-18 NPT |
7/16 in. |
0.4375 |
3/8-18 NPT |
37/64 in. |
0.5781 |
1/2-14 NPT |
23/32 in. |
0.7188 |
3/4-14 NPT |
59/64 in. |
0.9219 |
1-11-1/2 NPT |
1-5/32 in. |
1.1562 |
We stock taper pipe ThunderTaps from 1/8 to 1-1/2 NPT. Drills over 1/2 in., like the 37/64 in. for 3/8 NPT, are Silver and Deming bits with a 1/2 in. shank.
"Drill to the chart, not one size small. A tight tap hole doesn't make a stronger thread. It makes a broken tap, and a broken tap costs more than the part."
David Castro, President, Eldorado Tools
Drill size chart: decimal equivalents for every drill size
Every fractional, number, letter and metric drill from 1/64 in. to 1 in. sorted by size, with its decimal in inches and millimeters. Use this drill size chart to find the closest drill to any decimal, or to convert a number or letter drill to a fraction.
Drill size |
Type |
Decimal (in.) |
mm |
|---|---|---|---|
1/64 in. |
Fraction |
0.0156 |
0.397 |
0.5 mm |
Metric |
0.0197 |
0.5 |
1/32 in. |
Fraction |
0.0312 |
0.794 |
1 mm |
Metric |
0.0394 |
1 |
#60 |
Number (wire gauge) |
0.0400 |
1.016 |
#59 |
Number (wire gauge) |
0.0410 |
1.041 |
#58 |
Number (wire gauge) |
0.0420 |
1.067 |
#57 |
Number (wire gauge) |
0.0430 |
1.092 |
#56 |
Number (wire gauge) |
0.0465 |
1.181 |
3/64 in. |
Fraction |
0.0469 |
1.191 |
#55 |
Number (wire gauge) |
0.0520 |
1.321 |
#54 |
Number (wire gauge) |
0.0550 |
1.397 |
1.5 mm |
Metric |
0.0591 |
1.5 |
#53 |
Number (wire gauge) |
0.0595 |
1.511 |
1/16 in. |
Fraction |
0.0625 |
1.587 |
#52 |
Number (wire gauge) |
0.0635 |
1.613 |
#51 |
Number (wire gauge) |
0.0670 |
1.702 |
#50 |
Number (wire gauge) |
0.0700 |
1.778 |
#49 |
Number (wire gauge) |
0.0730 |
1.854 |
#48 |
Number (wire gauge) |
0.0760 |
1.93 |
5/64 in. |
Fraction |
0.0781 |
1.984 |
#47 |
Number (wire gauge) |
0.0785 |
1.994 |
2 mm |
Metric |
0.0787 |
2 |
#46 |
Number (wire gauge) |
0.0810 |
2.057 |
#45 |
Number (wire gauge) |
0.0820 |
2.083 |
#44 |
Number (wire gauge) |
0.0860 |
2.184 |
#43 |
Number (wire gauge) |
0.0890 |
2.261 |
#42 |
Number (wire gauge) |
0.0935 |
2.375 |
3/32 in. |
Fraction |
0.0938 |
2.381 |
#41 |
Number (wire gauge) |
0.0960 |
2.438 |
#40 |
Number (wire gauge) |
0.0980 |
2.489 |
2.5 mm |
Metric |
0.0984 |
2.5 |
#39 |
Number (wire gauge) |
0.0995 |
2.527 |
#38 |
Number (wire gauge) |
0.1015 |
2.578 |
#37 |
Number (wire gauge) |
0.1040 |
2.642 |
#36 |
Number (wire gauge) |
0.1065 |
2.705 |
7/64 in. |
Fraction |
0.1094 |
2.778 |
#35 |
Number (wire gauge) |
0.1100 |
2.794 |
#34 |
Number (wire gauge) |
0.1110 |
2.819 |
#33 |
Number (wire gauge) |
0.1130 |
2.87 |
#32 |
Number (wire gauge) |
0.1160 |
2.946 |
3 mm |
Metric |
0.1181 |
3 |
#31 |
Number (wire gauge) |
0.1200 |
3.048 |
1/8 in. |
Fraction |
0.1250 |
3.175 |
#30 |
Number (wire gauge) |
0.1285 |
3.264 |
#29 |
Number (wire gauge) |
0.1360 |
3.454 |
3.5 mm |
Metric |
0.1378 |
3.5 |
#28 |
Number (wire gauge) |
0.1405 |
3.569 |
9/64 in. |
Fraction |
0.1406 |
3.572 |
#27 |
Number (wire gauge) |
0.1440 |
3.658 |
#26 |
Number (wire gauge) |
0.1470 |
3.734 |
#25 |
Number (wire gauge) |
0.1495 |
3.797 |
#24 |
Number (wire gauge) |
0.1520 |
3.861 |
#23 |
Number (wire gauge) |
0.1540 |
3.912 |
5/32 in. |
Fraction |
0.1562 |
3.969 |
#22 |
Number (wire gauge) |
0.1570 |
3.988 |
4 mm |
Metric |
0.1575 |
4 |
#21 |
Number (wire gauge) |
0.1590 |
4.039 |
#20 |
Number (wire gauge) |
0.1610 |
4.089 |
#19 |
Number (wire gauge) |
0.1660 |
4.216 |
#18 |
Number (wire gauge) |
0.1695 |
4.305 |
11/64 in. |
Fraction |
0.1719 |
4.366 |
#17 |
Number (wire gauge) |
0.1730 |
4.394 |
#16 |
Number (wire gauge) |
0.1770 |
4.496 |
4.5 mm |
Metric |
0.1772 |
4.5 |
#15 |
Number (wire gauge) |
0.1800 |
4.572 |
#14 |
Number (wire gauge) |
0.1820 |
4.623 |
#13 |
Number (wire gauge) |
0.1850 |
4.699 |
3/16 in. |
Fraction |
0.1875 |
4.762 |
#12 |
Number (wire gauge) |
0.1890 |
4.801 |
#11 |
Number (wire gauge) |
0.1910 |
4.851 |
#10 |
Number (wire gauge) |
0.1935 |
4.915 |
#9 |
Number (wire gauge) |
0.1960 |
4.978 |
5 mm |
Metric |
0.1969 |
5 |
#8 |
Number (wire gauge) |
0.1990 |
5.055 |
#7 |
Number (wire gauge) |
0.2010 |
5.105 |
13/64 in. |
Fraction |
0.2031 |
5.159 |
#6 |
Number (wire gauge) |
0.2040 |
5.182 |
#5 |
Number (wire gauge) |
0.2055 |
5.22 |
#4 |
Number (wire gauge) |
0.2090 |
5.309 |
#3 |
Number (wire gauge) |
0.2130 |
5.41 |
5.5 mm |
Metric |
0.2165 |
5.5 |
7/32 in. |
Fraction |
0.2188 |
5.556 |
#2 |
Number (wire gauge) |
0.2210 |
5.613 |
#1 |
Number (wire gauge) |
0.2280 |
5.791 |
A |
Letter |
0.2340 |
5.944 |
15/64 in. |
Fraction |
0.2344 |
5.953 |
6 mm |
Metric |
0.2362 |
6 |
B |
Letter |
0.2380 |
6.045 |
C |
Letter |
0.2420 |
6.147 |
D |
Letter |
0.2460 |
6.248 |
1/4 in. |
Fraction |
0.2500 |
6.35 |
E |
Letter |
0.2500 |
6.35 |
6.5 mm |
Metric |
0.2559 |
6.5 |
F |
Letter |
0.2570 |
6.528 |
G |
Letter |
0.2610 |
6.629 |
17/64 in. |
Fraction |
0.2656 |
6.747 |
H |
Letter |
0.2660 |
6.756 |
I |
Letter |
0.2720 |
6.909 |
7 mm |
Metric |
0.2756 |
7 |
J |
Letter |
0.2770 |
7.036 |
K |
Letter |
0.2810 |
7.137 |
9/32 in. |
Fraction |
0.2812 |
7.144 |
L |
Letter |
0.2900 |
7.366 |
M |
Letter |
0.2950 |
7.493 |
7.5 mm |
Metric |
0.2953 |
7.5 |
19/64 in. |
Fraction |
0.2969 |
7.541 |
N |
Letter |
0.3020 |
7.671 |
5/16 in. |
Fraction |
0.3125 |
7.938 |
8 mm |
Metric |
0.3150 |
8 |
O |
Letter |
0.3160 |
8.026 |
P |
Letter |
0.3230 |
8.204 |
21/64 in. |
Fraction |
0.3281 |
8.334 |
Q |
Letter |
0.3320 |
8.433 |
8.5 mm |
Metric |
0.3346 |
8.5 |
R |
Letter |
0.3390 |
8.611 |
11/32 in. |
Fraction |
0.3438 |
8.731 |
S |
Letter |
0.3480 |
8.839 |
9 mm |
Metric |
0.3543 |
9 |
T |
Letter |
0.3580 |
9.093 |
23/64 in. |
Fraction |
0.3594 |
9.128 |
U |
Letter |
0.3680 |
9.347 |
9.5 mm |
Metric |
0.3740 |
9.5 |
3/8 in. |
Fraction |
0.3750 |
9.525 |
V |
Letter |
0.3770 |
9.576 |
W |
Letter |
0.3860 |
9.804 |
25/64 in. |
Fraction |
0.3906 |
9.922 |
10 mm |
Metric |
0.3937 |
10 |
X |
Letter |
0.3970 |
10.084 |
Y |
Letter |
0.4040 |
10.262 |
13/32 in. |
Fraction |
0.4062 |
10.319 |
Z |
Letter |
0.4130 |
10.49 |
10.5 mm |
Metric |
0.4134 |
10.5 |
27/64 in. |
Fraction |
0.4219 |
10.716 |
11 mm |
Metric |
0.4331 |
11 |
7/16 in. |
Fraction |
0.4375 |
11.112 |
11.5 mm |
Metric |
0.4528 |
11.5 |
29/64 in. |
Fraction |
0.4531 |
11.509 |
15/32 in. |
Fraction |
0.4688 |
11.906 |
12 mm |
Metric |
0.4724 |
12 |
31/64 in. |
Fraction |
0.4844 |
12.303 |
12.5 mm |
Metric |
0.4921 |
12.5 |
1/2 in. |
Fraction |
0.5000 |
12.7 |
13 mm |
Metric |
0.5118 |
13 |
33/64 in. |
Fraction |
0.5156 |
13.097 |
17/32 in. |
Fraction |
0.5312 |
13.494 |
13.5 mm |
Metric |
0.5315 |
13.5 |
35/64 in. |
Fraction |
0.5469 |
13.891 |
14 mm |
Metric |
0.5512 |
14 |
9/16 in. |
Fraction |
0.5625 |
14.287 |
14.5 mm |
Metric |
0.5709 |
14.5 |
37/64 in. |
Fraction |
0.5781 |
14.684 |
15 mm |
Metric |
0.5906 |
15 |
19/32 in. |
Fraction |
0.5938 |
15.081 |
39/64 in. |
Fraction |
0.6094 |
15.478 |
15.5 mm |
Metric |
0.6102 |
15.5 |
5/8 in. |
Fraction |
0.6250 |
15.875 |
16 mm |
Metric |
0.6299 |
16 |
41/64 in. |
Fraction |
0.6406 |
16.272 |
16.5 mm |
Metric |
0.6496 |
16.5 |
21/32 in. |
Fraction |
0.6562 |
16.669 |
17 mm |
Metric |
0.6693 |
17 |
43/64 in. |
Fraction |
0.6719 |
17.066 |
11/16 in. |
Fraction |
0.6875 |
17.462 |
17.5 mm |
Metric |
0.6890 |
17.5 |
45/64 in. |
Fraction |
0.7031 |
17.859 |
18 mm |
Metric |
0.7087 |
18 |
23/32 in. |
Fraction |
0.7188 |
18.256 |
18.5 mm |
Metric |
0.7283 |
18.5 |
47/64 in. |
Fraction |
0.7344 |
18.653 |
19 mm |
Metric |
0.7480 |
19 |
3/4 in. |
Fraction |
0.7500 |
19.05 |
49/64 in. |
Fraction |
0.7656 |
19.447 |
19.5 mm |
Metric |
0.7677 |
19.5 |
25/32 in. |
Fraction |
0.7812 |
19.844 |
20 mm |
Metric |
0.7874 |
20 |
51/64 in. |
Fraction |
0.7969 |
20.241 |
20.5 mm |
Metric |
0.8071 |
20.5 |
13/16 in. |
Fraction |
0.8125 |
20.637 |
21 mm |
Metric |
0.8268 |
21 |
53/64 in. |
Fraction |
0.8281 |
21.034 |
27/32 in. |
Fraction |
0.8438 |
21.431 |
21.5 mm |
Metric |
0.8465 |
21.5 |
55/64 in. |
Fraction |
0.8594 |
21.828 |
22 mm |
Metric |
0.8661 |
22 |
7/8 in. |
Fraction |
0.8750 |
22.225 |
22.5 mm |
Metric |
0.8858 |
22.5 |
57/64 in. |
Fraction |
0.8906 |
22.622 |
23 mm |
Metric |
0.9055 |
23 |
29/32 in. |
Fraction |
0.9062 |
23.019 |
59/64 in. |
Fraction |
0.9219 |
23.416 |
23.5 mm |
Metric |
0.9252 |
23.5 |
15/16 in. |
Fraction |
0.9375 |
23.812 |
24 mm |
Metric |
0.9449 |
24 |
61/64 in. |
Fraction |
0.9531 |
24.209 |
24.5 mm |
Metric |
0.9646 |
24.5 |
31/32 in. |
Fraction |
0.9688 |
24.606 |
25 mm |
Metric |
0.9843 |
25 |
63/64 in. |
Fraction |
0.9844 |
25.003 |
1 in. |
Fraction |
1.0000 |
25.4 |
Why does my tap keep breaking?
A tap usually breaks because the hole is too small, chips pack in the flutes, or the tap is forced at an angle. This table covers the common causes.
Problem |
Likely cause |
Fix |
|---|---|---|
Tap snaps in the hole |
Tap drill one size too small |
Drill to the chart size, or one size larger in hard steel |
Tap binds and squeaks |
Chips packed in the flutes, no oil |
Back the tap out a half turn every turn or two, use tapping oil |
Tap breaks at the bottom of a blind hole |
Tap bottomed out |
Drill deeper than the thread, and finish with a bottoming tap |
Thread is loose or stripped |
Hole too big, or worn tap |
Check the drill size, replace the tap |
Thread is crooked |
Tap started at an angle |
Start square with a tap guide or in a drill press |
FAQ
What size drill bit for a 1/4-20 tap?
Use a #7 drill (0.201 in.). A 13/64 in. drill (0.2031 in.) also works and cuts about 72% of a full thread.
What size drill bit for a 3/8-16 tap?
Use a 5/16 in. drill (0.3125 in.). For a 3/8-24 fine thread, use a Q drill (0.332 in.).
What size drill bit for a 5/16-18 tap?
Use an F drill (0.257 in.). For a 5/16-24 fine thread, use an I drill (0.272 in.).
What size drill bit for a 10-24 tap?
Use a #25 drill (0.1495 in.). A 10-32 tap takes a #21 drill (0.159 in.).
What is the tap drill for M6 and M8?
M6 x 1.0 takes a 5 mm drill (#9 is the nearest inch drill). M8 x 1.25 takes a 6.8 mm drill (letter H is close).
What size drill bit for a 1/4 in. Tapcon?
A 1/4 in. Tapcon concrete screw uses a 3/16 in. carbide masonry bit, and a 3/16 in. Tapcon uses a 5/32 in. bit. Drill the hole at least 1/2 in. deeper than the screw will go.
What is a wire gauge drill?
A wire gauge drill is a number drill, #1 (0.228 in.) down to #80. The number sizes come from an old steel wire gauge, so the bigger the number, the smaller the drill.
What is the difference between a taper, plug and bottoming tap?
They differ by how many threads are tapered at the tip. A taper tap starts easiest, a plug tap is the all-around choice, and a bottoming tap cuts threads to the bottom of a blind hole.
Need the right speed for these drills? See our drill speed chart. Choosing a bit for steel or stainless? Read How to Choose Drill Bits for Metal, or see every bit type in Types of Drill Bits Explained. Questions? Call (833) 4-ETOOLS or email sales@eldoradotools.com.
First published June 1, 2023. Rewritten Oct 2, 2026 with inch, metric and pipe tap drill charts, a corrected decimal chart (letter H is 0.266 in.), and priced drill and tap picks.
