List of drill and tap sizes

Schematic of a machine tap

Below is a comprehensive drill and tap size chart for all drills and taps, imperial and metric, up to 36.5 millimetres (1.44 in) in diameter.

In manufactured parts, holes with female screw threads are often needed; they accept male screws to facilitate the building and fastening of a finished assembly. One of the most common ways to produce such threaded holes is to drill a hole of appropriate size with a drill bit and then tap it with a tap. Each standard size of female screw thread has one or several corresponding drill bit sizes that are within the range of appropriate size—slightly larger than the minor diameter of the mating male thread, but smaller than its pitch and major diameters. Such an appropriately sized drill is called a tap drill for that size of thread, because it is a correct drill to be followed by the tap. Many thread sizes have several possible tap drills, because they yield threads of varying thread depth between 50% and 100%. Usually thread depths of 60% to 75% are desired.

People frequently use a chart such as this to determine the proper tap drill for a certain thread size or the proper tap for an existing hole.

Rules of thumb

Regarding the proportion of tap drill to thread major diameter, for standard V threads (ISO V thread and UTS V thread), there are several rules of thumb with strong predictive power:

• A good tap drill is 85% (± 2 pp) of major diameter for coarse threads, and
  A good tap drill is 90% (± 2 pp) of major diameter for fine threads.
• For metric V threads, the concept of major minus pitch (i.e., the major or widest diameter of the intended screw in millimeters minus the pitch of the threads of that screw in millimeters per thread) yields a good tap drill diameter.
  • The major minus pitch technique also works for inch-based threads, but you must first calculate the pitch by converting the fraction of threads-per-inch (TPI) into a decimal. For example, a screw with a pitch of 1/20 (20 threads per inch) has a pitch of .050 and a 1/13 pitch (13 threads per inch) has a pitch of .077. Your result will only land near a tap drill size (not directly on one).
• For both of these rules of thumb (85%/90% and major minus pitch), the tap drill size yielded is not necessarily the only possible one, but it is a good one for general use.
• The 85%/90% rule works best in the range of 1/4"-1" (6 to 25 mm), the sizes most important on many shop floors. Some sizes outside that range have different ratios.

Below, these guidelines are explored with examples.

Examples

• A good tap drill is 85% (± 2 pp) of major diameter for coarse threads, and
  a good tap drill is 90% (± 2 pp) of major diameter for fine threads.
  • Example (inch, coarse): For size 7/16 (this is the diameter of the intended screw in fraction form)-14 (this is the number of threads per inch— "14" is considered "coarse"), .437" × .85 = .371". Therefore, a size 7/16 screw (7/16=.437) with 14 threads per inch (coarse) needs a tap drill with a diameter of about .371 inches.
    • The drill sizes that are near this are letter U (.368"; 84.2%), 9.5 mm (.374; 85.6%), and 3/8" (.375; 85.8%); any of these will work well.
  • Example (inch, fine): For 7/16-20 (same diameter as the previous example, but this time with 20 threads per inch, which is considered "fine"), .437" × .90 = .393" (i.e., if the threads are to be fine, then a slightly larger diameter drill bit should be used before tapping the hole for the screw).
    • The drill sizes that are near this are 25/64" (.391"; 89.4%), 10 mm (.393"; 90%), and letter X (.397"; 90.8%); any of these will work well.
  • Example (metric, coarse): For M7.0 × 1.0 (an intended screw with a diameter of 7.0 mm and a pitch of 1 mm between each thread, which is considered "coarse"), 7.0 × .85 = 5.95.
    • The drill sizes that are near this are 15/64" (85%), 6.0 mm (85.7%), and 6.1 mm (87.1%); any of these will work well.
  • Example (metric, fine): For M7.0 × 0.5, 7.0 × .90 = 6.30.
    • The drill sizes that are near this are 6.3 mm (90%), 1/4" (90.7%), 6.4 mm (91.4%), and 6.5 mm (92.9%); any of these will work well.
• For metric V threads, major minus pitch yields a good tap drill diameter.
  • Example (metric, coarse): For M7.0 × 1.0, 7.0 − 1.0 = 6.0
  • Example (metric, fine): For M7.0 × 0.5, 7.0 − 0.5 = 6.5
    • (The 85%:90%::C:F guideline, within its effective range, matches this in net effect)
  • The major minus pitch also works for inch-based threads, but you must first determine the pitch by looking at the number of treads per inch (TPI)(for example, 1/20 = .050 and 1/13 = .077), and your result will only land near a tap drill size (not directly on one).
  • Example (inch coarse): For 7/16-14, 1" ÷ 14 = .071"; .437" − .071" = .366";
    • The drill sizes that are near this are 9.3 mm (.366") and letter U (.368"). In addition, 9.5 mm (.374), and 3/8" (.375) will work well, although "major minus pitch" by itself does not tell you this; but the 85% ± 2 pp guideline supports it.
  • Example (inch fine): For 7/16-20, 1" ÷ 20 = .050"; .437" − .050" = .387";
    • The drill sizes that are near this are letter W (.386") and 25/64" (.391"). In addition, 10 mm (.393"), and letter X (.397") will work well, although "major minus pitch" by itself does not tell you this; but the 90% ± 2 pp guideline supports it.
• For both of these rules of thumb (85%/90% and major minus pitch), the tap drill size yielded is not necessarily the only possible one, but it is a good one for general use.
  • Example (metric coarse): For M7.0 × 1.0, major minus pitch yields 6.0, but 6.1 also works well.
  • Example (metric fine): For M7.0 × 0.5, major minus pitch yields 6.5, which at 92.9% happens to be an example that pushes over the outer bound of the 90% ± 2 pp, but "major minus pitch" is still valid, although smaller drills (6.3 mm, 1/4", 6.4 mm) will work well.

Chart

  Inch-sized drills, increments of 1/64 in.

  Drills in the number (1-80) and letter (A-Z) series which are specified in decimal inches.

  Standard metric drill sizes.

  Standard metric drill sizes used for metric taps of the size indicated in the tap size column.

Drill bit diameter		Fractional size	Drill wire  gauge[1][2]	Tap size[3][4][5]	Clearance		Theoretical percentage^† of thread[6][7]	Outer diameter
(mm, 4 d.p.)	(in, 5 d.p.)	(in)			Close fit[8]	Free fit[9]	(%)
0.0483	0.00190		107
0.0500	0.00197
0.0584	0.00230		106
0.0686	0.00270		105
0.0787	0.00310		104
0.0889	0.00350		103
0.0991	0.00390		102
0.1000	0.00394
0.1092	0.00430		101
0.1194	0.00470		100
0.1295	0.00510		99
0.1397	0.00550		98
0.1499	0.00590		97
0.1600	0.00630		96
0.1702	0.00670		95
0.1803	0.00710		94
0.1905	0.00750		93
0.2007	0.00790		92
0.2000	0.00787
0.2108	0.00830		91
0.2210	0.00870		90
0.2311	0.00910		89
0.2413	0.00950		88
0.2500	0.00984
0.2540	0.01000		87
0.2667	0.01050		86
0.2794	0.01100		85
0.2921	0.01150		84
0.3000	0.01181
0.3048	0.01200		83
0.3175	0.01250		82
0.3302	0.01300		81
0.3429	0.01350		80
0.3500	0.01378
0.3680	0.01449		79
0.3969	0.01563	1/64		#0000-160^‡	0.02400"			0.021 in
0.4000	0.01575
0.4064	0.01600		78
0.4200	0.01654
0.4400	0.01732
0.4500	0.01772
0.4572	0.01800		77
0.4600	0.01811
0.4800	0.01890
0.5000	0.01969
0.5080	0.02000		76
0.5334	0.02100		75
0.5500	0.02165
0.5715	0.02250		74
0.6000	0.02362
0.6096	0.02400		73
0.6350	0.02500		72
0.6500	0.02559
0.6604	0.02600		71	#000-120^‡	0.03700"
0.7000	0.02756
0.7112	0.02800		70
0.7417	0.02920		69
0.7500	0.02953
0.7874	0.03100		68
0.7938	0.03125	1/32
0.8000	0.03150
0.8128	0.03200		67
0.8382	0.03300		66
0.8500	0.03346
0.8890	0.03500		65	#00-90^‡	0.05200"
0.9000	0.03543
0.9144	0.03600		64
0.9398	0.03700		63
0.9500	0.03740
0.9652	0.03800		62
0.9906	0.03900		61
1.0000	0.03937
1.0160	0.04000		60
1.0414	0.04100		59
1.0500	0.04134
1.0668	0.04200		58
1.0922	0.04300		57
1.1000	0.04331
1.1500	0.04528
1.1811	0.04650		56
1.1906	0.04688	3/64		#0-80	0.06350"	0.07000"
1.2000	0.04724
1.2500	0.04921
1.3000	0.05118
1.3208	0.05200		55
1.3500	0.05315
1.3970	0.05500		54
1.4000	0.05512
1.4500	0.05709
1.5000	0.05906
1.5113	0.05950		53	#1-64, #1-72	0.07600"	0.08100"
1.5500	0.06102
1.5875	0.06250	1/16
1.6000	0.06299			M2x0.4	2.2mm
1.6129	0.06350		52
1.6500	0.06496
1.7000	0.06693
1.7018	0.06700		51	#2-56	0.08900"	0.09600"
1.7500	0.06890			M2.2x0.45	2.25mm
1.7780	0.07000		50	#2-56, #2-64	0.08900"	0.09600"
1.8000	0.07087
1.8500	0.07283
1.8542	0.07300		49
1.9000	0.07480
1.9304	0.07600		48
1.9500	0.07677
1.9600	0.07717			#3-48	0.10400"	0.11000"	81
1.9700	0.07756			#3-48	0.10400"	0.11000"	79
1.9844	0.07813	5/64		#3-48	0.10400"	0.11000"	78
1.9939	0.07850		47	#3-48	0.10400"	0.11000"	76
2.0000	0.07874			#3-48	0.10400"	0.11000"	75
2.0100	0.07913			#3-48	0.10400"	0.11000"	74
2.0200	0.07953			#3-48	0.10400"	0.11000"	72
2.0300	0.07992			#3-48	0.10400"	0.11000"	71
2.0400	0.08031			#3-48 #3-56	0.10400"	0.11000"	69 81
2.0500	0.08071			#3-48 #3-56 M2.5x0.45	0.10400"	0.11000"	68 79
2.0574	0.08100		46	#3-48 #3-56	0.10400"	0.11000"	66 77
2.0700	0.08150			#3-48 #3-56	0.10400"	0.11000"	65 75
2.0828	0.08200		45	#3-48 #3-56	0.10400"	0.11000"	66 74
2.0900	0.08228			#3-48 #3-56	0.10400"	0.11000"	62 72
2.1000	0.08268			#3-48 #3-56	0.10400"	0.11000"	60 70
2.1100	0.08307			#3-48 #3-56	0.10400"	0.11000"	59 69
2.1200	0.08346			#3-56	0.10400"	0.11000"	67
2.1300	0.08386			#3-56	0.10400"	0.11000"	65
2.1400	0.08425			#3-56	0.10400"	0.11000"	63
2.1500	0.08465			#3-56 M2.5x0.35	0.10400"	0.11000"	62
2.1600	0.08504			#3-56	0.10400"	0.11000"	60
2.1700	0.08543			#3-56	0.10400"	0.11000"	59
2.1844	0.08600		44	#4-36	0.11600"	0.12850"	81
2.1900	0.08622			#4-40	0.11600"	0.12850"	81
2.2000	0.08661			#4-40	0.11600"	0.12850"	78
2.2100	0.08701			#4-40	0.11600"	0.12850"	77
2.2200	0.08740			#4-40	0.11600"	0.12850"	76
2.2300	0.08780			#4-40	0.11600"	0.12850"	75
2.2400	0.08819			#4-40	0.11600"	0.12850"	73
2.2500	0.08858			#4-40	0.11600"	0.12850"	72
2.2600	0.08898			#4-40	0.11600"	0.12850"	71
2.2606	0.08900		43	#4-40	0.11600"	0.12850"	71
2.2700	0.08937			#4-40	0.11600"	0.12850"	70
2.2800	0.08976			#4-40	0.11600"	0.12850"	68
2.2900	0.09016			#4-40 #4-48	0.11600"	0.12850"	67 81
2.3000	0.09055			#4-40 #4-48	0.11600"	0.12850"	66 79
2.3100	0.09094			#4-40 #4-48	0.11600"	0.12850"	65 78
2.3200	0.09134			#4-40 #4-48	0.11600"	0.12850"	64 76
2.3300	0.09173			#4-40 #4-48	0.11600"	0.12850"	63 75
2.3400	0.09213			#4-40 #4-48	0.11600"	0.12850"	61 74
2.3500	0.09252			#4-40 #4-48	0.11600"	0.12850"	60 72
2.3749	0.09350		42	#4-48	0.11600"	0.12850"	69
2.3813	0.09375	3/32
2.4000	0.09449
2.4384	0.09600		41
2.4500	0.09646
2.4892	0.09800		40
2.5000	0.09843			M3x0.5	3.2mm		75
2.5273	0.09950		39	#5-40	0.12850"	0.13600"	78
2.5781	0.10150		38	#5-40	0.12850"	0.13600"	72
2.6000	0.10236
2.6416	0.10400		37	#5-44	0.12850"	0.13600"	71
2.7000	0.10630
2.7051	0.10650		36	#6-32	0.14400"	0.14950"	77	.14
2.7500	0.10827
2.7781	0.10938	7/64
2.7940	0.11000		35
2.8000	0.11024
2.8194	0.11100		34
2.8702	0.11300		33	#6-40		.1563		.14
2.9000	0.11417			M3.5x0.6
2.9464	0.11600		32
3.0000	0.11811
3.0480	0.12000		31
3.1000	0.12205
3.1750	0.12500	1/8
3.2000	0.12598
3.2500	0.12795
3.2639	0.12850		30
3.3000	0.12992			M4x0.7	4.10mm		75
3.4000	0.13386
3.4544	0.13600		29	#8-32	0.16950"	0.17700"	69
3.5000	0.13780			M4x0.7	4.10mm		60
3.5687	0.14050		28
3.5719	0.14063	9/64
3.6000	0.14173
3.6576	0.14400		27
3.7000	0.14567
3.7338	0.14700		26
3.7500	0.14764
3.7973	0.14950		25	#10-24	0.19600"	0.20100"	75
3.8000	0.14961
3.8608	0.15200		24
3.9000	0.15354
3.9116	0.15400		23
3.9688	0.15625	5/32
3.9878	0.15700		22
4.0000	0.15748
4.0386	0.15900		21	#10-32	0.1960"	0.2010"
4.0894	0.16100		20
4.1000	0.16142
4.2000	0.16535			M5x0.8	5.10mm		75
4.2164	0.16600		19
4.2500	0.16732
4.3053	0.16950		18
4.3656	0.17188	11/64
4.3942	0.17300		17
4.4000	0.17323
4.4958	0.17700		16	#12-24	0.22100"	0.22800"	72
4.5000	0.17717
4.5720	0.18000		15
4.6000	0.18110
4.6228	0.18200		14
4.6990	0.18500		13
4.7000	0.18504
4.7500	0.18701
4.7625	0.18750	3/16
4.8000	0.18898
4.8006	0.18900		12
4.8514	0.19100		11
4.9000	0.19291
4.9149	0.19350		10
4.9784	0.19600		9
5.0000	0.19685			M6x1.0	6.10mm		75
5.0546	0.19900		8
5.1000	0.20079
5.1054	0.20100		7	1/4-20	0.25700"	0.26600"	72
5.1594	0.20313	13/64
5.1816	0.20400		6
5.2000	0.20472			M6x0.75 [10]	6.10mm		60
5.2197	0.20550		5
5.2500	0.20669
5.3000	0.20866
5.3086	0.20900		4
5.4000	0.21260
5.4102	0.21300		3	1/4-28	0.25700"	0.26600"	80
5.5000	0.21654			1/4-28	0.25700"	0.26600"	70
5.5563	0.21875	7/32		1/4-28 1/4-32 ^(1/4-32 UNEF for Glow plug)	0.25700"	0.26600"	68
5.6000	0.22047			1/4-28	0.25700"	0.26600"	63
5.6134	0.22100		2	1/4-28	0.25700"	0.26600"	60
5.7000	0.22441
5.7500	0.22638
5.7912	0.22800		1
5.8000	0.22835
5.9000	0.23228
5.9436	0.23400		A
5.9531	0.23438	15/64
6.0000	0.23622
6.0452	0.23800		B
6.1000	0.24016			M7x1.0			75
6.1468	0.24200		C
6.2000	0.24409
6.2484	0.24600		D
6.2500	0.24606
6.3000	0.24803
6.3500	0.25000	1/4
			E
6.4000	0.25197
6.5000	0.25591			M7X0.5
6.5278	0.25700		F	5/16-18	0.32300"	0.33200"	77
6.6000	0.25984
6.6294	0.26100		G
6.7000	0.26378
6.7469	0.26563	17/64		5/16-18			74
6.7500	0.26575
6.7564	0.26600		H
6.8000	0.26772
6.9000	0.27165			M8x1.25			75
6.9088	0.27200		I	5/16-24	0.32300"	0.33200"	75
7.0000	0.27559
7.0358	0.27700		J	5/16-18			50
7.1000	0.27953			M8x1.0			75
7.1374	0.28100		K
7.1438	0.28125	9/32		5/16-32
7.2000	0.28346
7.2500	0.28543
7.3000	0.28740
7.3660	0.29000		L
7.4000	0.29134
7.4930	0.29500		M
7.5000	0.29528
7.5406	0.29688	19/64
7.6000	0.29921
7.6708	0.30200		N
7.7000	0.30315
7.7500	0.30512
7.8000	0.30709
7.9000	0.31102
7.9375	0.31250	5/16		3/8-16	0.38600"	0.39700"	77
8.0000	0.31496
8.0264	0.31600		O
8.1000	0.31890
8.2000	0.32283
8.2042	0.32300		P
8.2500	0.32480
8.3000	0.32677
8.3344	0.32813	21/64
8.4000	0.33071
8.4328	0.33200		Q	3/8-24	0.38600"	0.39700"	79
8.5000	0.33465			M10x1.5
8.6000	0.33858
8.6106	0.33900		R
8.7000	0.34252
8.7313	0.34375	11/32
8.7500	0.34449			M10x1.25
8.8000	0.34646
8.8392	0.34800		S
8.9000	0.35039
9.0000	0.35433			M10x1.0 ^(spark plug)
9.0932	0.35800		T
9.1000	0.35827
9.1281	0.35938	23/64
9.2000	0.36220
9.2500	0.36417
9.3000	0.36614
9.3472	0.36800		U	7/16-14	0.45310"	0.46870"	75
9.4000	0.37008
9.5000	0.37402
9.5250	0.37500	3/8
9.5758	0.37700		V
9.6000	0.37795
9.7000	0.38189
9.7500	0.38386
9.8000	0.38583
9.8044	0.38600		W
9.9000	0.38976
9.9219	0.39063	25/64		7/16-20	0.45313"	0.46785"	72
10.0000	0.39370
10.0838	0.39700		X
10.2616	0.40400		Y
10.3188	0.40625	13/32		7/16 - 40
10.4902	0.41300		Z
10.5000	0.41339			M12x1.75			75
10.7000	0.42126			M12x1.5			75
10.7156	0.42188	27/64		1/2-13	0.51563"	0.53125"	78
10.900	0.42913			M12X1.25 ^(spark plug)
11.0000	0.43307
11.1125	0.43750	7/16
11.5000	0.45276
11.5094	0.45313	29/64		1/2-20	0.51563"	0.53125"	72
11.9063	0.46875	15/32		9/16-12	0.56250"		87
12.0000	0.47244
12.2000	0.48031			M14x2			75
12.3031	0.48438	31/64		9/16-12	0.56250"		68
12.5000	0.49213
12.7000	0.50000	1/2		9/16-18	0.56250"		87
				M14x1.5			75
12.8000	0.50393			M14x1.25 ^(spark plug)
13.0000	0.51181
13.0969	0.51563	33/64		9/16-18	0.56250"		65
13.4938	0.53125	17/32		5/8-11	0.62500"		79
13.5000	0.53150
13.8906	0.54688	35/64		5/8-11	0.62500"		66
14.0000	0.55118
14.2000	0.55906			M16x2			75
14.2875	0.56250	9/16		5/8-18	0.62500"		87
14.5000	0.57087
14.6844	0.57813	37/64		5/8-18	0.62500"		65
14.7000	0.57874			M16x1.5			75
15.0000	0.59055
15.0813	0.59375	19/32
15.4781	0.60938	39/64
15.5000	0.61024
15.8750	0.62500	5/8
16.0000	0.62992
16.2719	0.64063	41/64		3/4-10			84
16.5000	0.64961
16.6688	0.65625	21/32		3/4-10			72
16.8000	0.66141			M18x1.5 ^(spark plug)
17.0000	0.66929
17.0656	0.67188	43/64
17.4625	0.68750	11/16		3/4-16			77
17.5000	0.68898
17.8594	0.70313	45/64
18.0000	0.70866
18.2563	0.71875	23/32
18.5000	0.72835
18.6531	0.73438	47/64
19.0000	0.74803
19.0500	0.75000	3/4
19.4469	0.76563	49/64		7/8-9			76
19.5000	0.76772
19.8438	0.78125	25/32		7/8-9			65
20.0000	0.78740
20.2406	0.79688	51/64		7/8-14			84
20.5000	0.80709
20.6375	0.81250	13/16		7/8-14			67
21.0000	0.82677
21.0344	0.82813	53/64		7/8-18 NS ^(spark plug)
21.4313	0.84375	27/32
21.5000	0.84646
21.8281	0.85938	55/64		1-8			87
22.0000	0.86614
22.2250	0.87500	7/8		1-8			77
22.5000	0.88583
22.6219	0.89063	57/64		1-8			67
23.0000	0.90551
23.0188	0.90625	29/32		1-12			87
23.4156	0.92188	59/64		1-12 1-14			72 84
23.5000	0.92520
23.8125	0.93750	15/16		1-14			67
24.0000	0.94488
24.2094	0.95313	61/64
24.5000	0.96457
24.6063	0.96875	31/32		1 1/8-7			84
25.0000	0.98425
25.0031	0.98438	63/64		1 1/8-7			76
25.4000	1.00000	1		1 1/8-7			67
25.5000	1.00394
25.7969	1.01563	1 1/64
26.0000	1.02362
26.1938	1.03125	1 1/32		1 1/8-12			87
26.5000	1.04331
26.5906	1.04688	1 3/64		1 1/8-12			72
26.9875	1.06250	1 1/16
27.0000	1.06299
27.5000	1.08268
28.0000	1.10236
28.1781	1.10938	1 7/64		1 1/4-7			76
28.5000	1.12205
28.5750	1.12500	1 1/8		1 1/4-7			67
29.0000	1.14173
29.3688	1.15625	1 5/32		1 1/4-12			87
29.5000	1.16142
29.7656	1.17188	1 11/64		1 1/4-12			72
30.0000	1.18110
30.1625	1.18750	1 3/16		1 3/8-6			87
30.5000	1.20079
30.5594	1.20313	1 13/64		1 3/8-6			79
30.9563	1.21875	1 7/32		1 3/8-6			72
31.0000	1.22047
31.3531	1.23438	1 15/64		1 3/8-6			65
31.5000	1.24016
32.0000	1.25984
32.5000	1.27953
32.5438	1.28125	1 9/32		1 3/8-12			87
32.9406	1.29688	1 19/64		1 3/8-12			72
33.0000	1.29921
33.3375	1.31250	1 5/16		1 1/2-6			87
33.5000	1.31890
33.7344	1.32813	1 21/64		1 1/2-6			79
34.0000	1.33858
34.1313	1.34375	1 11/32		1 1/2-6			72
34.5000	1.35827
34.5281	1.35938	1 23/64		1 1/2-6			65
35.0000	1.37795
35.5000	1.39764
35.7188	1.40625	1 13/32		1 1/2-12			87
36.0000	1.41732
36.1156	1.42188	1 27/64		1 1/2-12			72
36.5000	1.43701

^†If theoretical thread percentage not given, assume 75% ± 10%
  Theoretical percentage of thread should not be relied upon for threads of included angles other than 60 degrees.
^‡See http://www.newmantools.com/taps/micro.htm for more information.

See also

• AN thread
• British standard pipe thread
• British Association screw threads
• British Standard Whitworth
• Drill bit sizes -a similar page including center drill sizes
• ISO metric screw thread
• National pipe thread
• Taps and dies
• United States Standard thread
• Unified Thread Standard

References

1. "Continuous Drill Bit Sizes". Archived from the original on 2006-07-19. Retrieved 2006-08-29.
2. "Decimal Equivalents". Ohio State University. Archived from the original on 2006-09-02. Retrieved 2006-08-29. External link in |work= (help)
3. "Tap Drill Sizes and Calculator". newmantools.com. Retrieved 2006-08-04. External link in |work= (help)
4. "Tap Drill Sizes for Universal and M-Profile Screw Threads". precisiontwistdrill.com. Retrieved 2006-08-04. External link in |work= (help)
5. "NC, NF, NEF to one inch in diameter". Sizes.com. Retrieved 2006-09-01. External link in |work= (help)
6. "High performance taps" (PDF). guhring.com. Retrieved 2010-10-07. External link in |publisher= (help)
7. "Tap Drill Sizes". widell.com. Retrieved 2006-09-01. External link in |work= (help)
8. "Tap & Clearance Drills For Common Screws". Small Parts Inc. Retrieved 2010-10-07. External link in |work= (help)
9. "Tap Drill Sizes". efunda.com. Retrieved 2006-08-04. External link in |work= (help)
10. http://www.littlemachineshop.com/reference/tapdrillsizes.pdf

External links

• Tap Drill Sizes
• Metric Tap Drill Sizes
• Tap and drill chart
• BTA Drill Tube Reference Chart