Fasteners 101 — Reference Tables

Quick, printable reference for conversions, thread pitch, drill sizes, tensile strength, hardness, and sizing. Use these guides to identify and size fasteners; always confirm against your project specifications or an engineer before final selection.

Reference Index

Quick Charts & Printable Tools

Tip: Set your PDF viewer to “Actual size” before printing to maintain scale.

US Tap & Drill Bit Size and Reference Chart (PDF)

US Drill Bit Size Conversion (PDF)

Fastener Industry Acronyms (PDF)

Rivet Sizing Chart (PDF)

Thread Identification Chart (PDF)

Thread Cutting Screws — Recommended Drill Bits (PDF)

Allen Key Specs — Imperial (PDF)

Allen Key Specs — Metric (PDF)

US Nut Size Charts

PDF Thumbnail US-serrated-flange-nut size chart

US Serrated Flange Nut Size Chart (PDF) - Print Friendly, 108Kb

PDF Thumbnail US nylon inserted hex lock nut size chart

US Nylon Inserted Hex Lock Nut Size Chart (PDF) - Print Friendly, 176Kb

US Hex Jam Nut Size Chart (PDF) - Print Friendly, 100Kb

PDF Thumbnail US machine screw hex nut size chart

US Machine Screw Hex Nut Size Chart (PDF) - Print Friendly, 57Kb

Metric Nut Size Charts

PDF Thumbnail metric flange nut size chart

Metric Serrated Flange Nut Size Chart (PDF) - Print Friendly, 55Kb

PDF Thumbnail metric hex jam nut size chart

Metric Hex Jam Nut Size Chart (PDF) - Print Friendly, 108Kb

Metric Hex Nut Size Chart (PDF) - Print Friendly, 137Kb

USS & SAE Washer Size Charts

PDF Thumbnail USS flat washer size chart

USS FLAT WASHERS Size Chart (PDF) - Print Friendly, 173Kb

PDF Thumbnail SAE flat washer size chart

SAE FLAT WASHERS Size Chart (PDF) - Print Friendly, 173Kb

Metric Washer Size Charts

PDF Thumbnail metric flat washer size chart

METRIC FLAT WASHERS Size Chart (PDF) - Print Friendly, 163Kb

Allen Key Specifications (ASME B18.3-2012)

Imperial Allen Keys (PDF)

Metric Allen Keys (PDF)

DIAMETER & THREAD PITCH CONVERSIONS

INCH		METRIC		CONVERSION (Diameter)
COARSE (UNC)	FINE (UNF)	COARSE (UNC)	FINE (UNF)	INCH	METRIC
1/4"-20	1/4"-28	M6-1.00	M6-0.75	1/4"	M6
5/16"-18	5/16"-24	M8-1.25	M8-1.00	5/16"	M8
3/8"-16	3/8"-24	M10-1.50	M10-1.25	3/8"	M10
7/16"-14	7/16"-20	M12-1.75	M12-1.50	1/2"	M12
1/2"-13	1/2"-20	M14-2.00	M14-1.50	5/8"	M16
9/16"-12	9/16"-18	M16-2.00	M16-1.50	3/4"	M20
5/8"-11	5/8"-18	M20-2.50	M20-1.50	7/8"	M22
3/4"-10	3/4"-10	M22-2.50	M22-1.50	1"	M24
7/8"-9	7/8"-14	M24-3.00	M24-2.00	1-1/8"	M27
1"-8	1"-14	M27-3.00	M27-2.00	1-1/4"	M30
1-1/8"-7	1-1/8"-12	M30-3.50	M30-2.00	1-3/8"	M33
1-1/4"-7	1-1/4"-12	M36-4.00	M36-2.00	1-1/2"	M36
1-3/8"-6	1-3/8"-12	M42-4.50	M42-2.00	1-3/4"	M42
1-1/2"-6	1-1/2"-12	M48-5.00	M48-2.00	2"	M48

Tensile Strength Comparison — Imperial Grades vs Metric Classes

Imperial Grades IBF/IN2 (PSI)	Metric Classes MPA (N/MM2)
L9 -- 180,000 PSI -- HIGH TENSILE	CLASS 12.9 -- 1,200 MPA -- HIGH TENSILE
SAE GRADE 8 -- 150,000 PSI -- HIGH TENSILE	CLASS 10.9 -- 1,034 MPA-- HIGH TENSILE
SAE GRADE 5 -- 120,000 PSI -- HIGH TENSILE	CLASS 8.8 -- 827 MPA-- HIGH TENSILE
STAINLESS CLASS 80 (304--316) -- 116,000 PSI	STAINLESS CLASS 80 (304-316) -- 800 MPA
STAINLESS CLASS 70 (304-316) 101,000 PSI	STAINLESS CLASS 70 (304-316) -- 700 MPA
STAINLESS CLASS 50 (NO MARKINGS) -- 72,000 PSI	STAINLESS CLASS 50 (NO MARKINGS) -- 500 MPA
LOW CARBON -- 62,000 PSI	427 MPA
58,015 PSI	CLASS 4.6 - 400 MPA

Hardness Reference (S/C Case & Core)

Screw Type	S Surface & C Case Hardness	Core Hardness (After Temper)	Material
Tapping Type A/AB/B	(S)Rockwell C45 min	Rockwell C28-38	AISI 1016-1024 or Equivalent Steel
Self Tapping Hi-Lo	(C)Rockwell C45 min	Rockwell C28-36	AISI 1019-1022 or Equivalent Steel
Thread Cutting Type 25/23/F	(S)Rockwell C45 min	Rockwell C28-38	AISI 1016-1024 or Equivalent Steel
Type F Torx Floorboard Screws	(S)Rockwell C45 min	Rockwell C28-38	AISI 1016-1024 or Equivalent Steel
Tri-Lobular Thread Rolling	(C)Rockwell C45 min	Rockwell C28-38	AISI 1016-1024 or Equivalent Steel
Self Piercing Screws	(S)Rockwell C45 min	Rockwell C28-38	AISI 1018-1022 or Equivalent Steel
Self Drilling Screws	(C)Rockwell C52-58	Rockwell C32-40	AISI 1016-1024 or Equivalent Steel

Screw Size Conversion (Number ↔ Fraction ↔ Decimal)

Screw Size	Fraction	Decimal
#1	1/16	0.0625
#2	5/64	0.0781
#3	3/32	0.0937
#4	7/64	0.1093
#5	1/8	0.125
#6	9/64	0.1406
#8	5/32	0.1562
#9	11/64	0.1718
#10	3/16	0.1875
#11	13/64	0.1718
#12	7/32	0.2187
#13	15/64	0.2343
#14	1/4	0.25
#16	17/64	0.2656
#18	17/64	0.2968
#20	5/16	0.3125
#24	3/8	0.375

US Tap & Drill Bit Size and Reference Chart

Machine Screw Size	Number of Threads Per Inch	Major Diameter	Minor Diameter	Tap drills				Clearance Drill
				75% Thread for Aluminum, Brass, & Plastics		50% Thread for Steel, Stainless, & Iron		Close Fit		Free Fit
				Drill Size	Decimal Equiv.	Drill Size	Decimal Equiv.	Drill Size	Decimal Equiv.	Drill Size	Decimal Equiv.
0	80	.0600	.0447	3/64	.0469	55	.0520	52	.0635	50	.0700
1	64	.0730	.0538	53	.0595	1/16	.0625	48	.0760	46	.0810
1	72	.0730	.0560	53	.0595	52	.0635
2	56	.0860	.0641	50	.0700	49	.0730	43	.0890	41	.0960
2	64	.0860	.0668	50	.0700	48	.0760
3	48	.0900	.0734	47	.0785	44	.0860	37	.1040	35	.1100
3	56	.0900	.0771	45	.0820	43	.0890
4	40	1120	.0813	43	.0890	41	.0960	32	.1160	30	.1285
4	48	1120	.0864	42	.0935	40	.0980
5	40	1250	.0943	38	.1015	7/64	.1094	30	.1285	29	.1360
5	44	1250	.0971	37	.1040	35	.1100
6	32	.1380	.0997	36	.1065	32	.1160	27	.1440	25	.1495
6	40	.1380	.1073	33	.1130	31	.1200
8	32	.1640	.1257	29	.1360	27	.1440	18	.1695	16	.1770
8	36	.1640	.1299	29	.1360	26	.1470
10	24	1900	.1389	25	.1495	20	.1610	9	.1960	7	.2010
10	32	1900	.1517	21	.1590	18	.1695

Thread Identification — US & Metric

Thread Identification — Quick Lookup

Prefer a printable? See the Thread Identification Chart (PDF).

Acronyms:
UNC - Unified National Coarse UNF - Unified National Fine UNEF - Unified National Extra Fine UNM - Unified National Miniature NPT - National Pipe Tapered	* - ISO Standard-1st Choice - ISO Standard-2nd Choice * - ISO Standard-3rd Choice X - DIN (German Standard)

Basic Major Diameter		US Standard					Metric
Inch	mm	Nominal Diameter mm	UNC (TPI)	UNF (TPI)	UNEF (TPI)	UNM (TPI)	Nominal Diameter mm	Standards	Pitch — Coarse (mm)	Pitch — Fine (mm)	Pitch — M Taper (mm)
.0118	0.30	0.30				318		X	0.075
.0138	0.35	0.35				282		*	0.080
.0146	0.37					254
.0157	0.40	0.40						*X	0.100
.0165	0.42
.0177	0.45	0.45				254		**	0.100
.0189	0.48
.0197	0.50	0.50				203		*X	0.125
.0209	0.53			160
.0213	0.54
.0217	0.55	0.55				203		**	0.125
.0236	0.60	0.60				169		*X	0.150
.0244	0.62
.0276	0.70	0.70				145			0.175
.0311	0.79
.0315	0.80	0.80				127		*X	0.200
.0340	0.86			120
.0354	0.90	0.90				113		**X	0.225
.0394	1.00	1.00				102		*X	0.250	0.2
.0433	1.10	1.10				102		**	0.250	0.2
.0470	1.19			90	96
.0472	1.20	1.20						*X	0.250	0.2
.0512	1.30
.0551	1.40	1.40				85		**X	0.300	0.2
.0591	1.50	1.50							0.300
.0600	1.52			80
.0629	1.60	1.60						*	0.350	0.2
.0669	1.70	1.70						X	0.350	0.2,0.25
.0709	1.80	1.80						**	0.350	0.2
.0730	1.85	#1		64	72
.0748	1.90
.0787	2.00	2.00						*X	0.400	0.25,0.35
.0860	2.18	#2		56	64
.0866	2.20	2.20						**	0.450	0.25
.0906	2.30	2.30						X	0.400	0.25,0.35
.0984	2.50	2.50						*	0.45	0.35
.0990	2.51	#3		48	56
.1024	2.60	2.60						X	0.45	0.25,0.35
.1102	2.80
.1120	2.84	#4		40	48
.1181	3.00	3.00						*X	0.50	0.35
.1250	3.18	#5		40	44
.1260	3.20
.1380	3.50	#6		32	40		3.50	**X	0.60	0.35,0.5
.1417	3.60
.1575	4.00						4.00	*X	0.70	0.5,0.75
.1614	4.10
.1640	4.17	#8		32	36
.1772	4.50						4.50	**	0.75	0.5
.1850	4.70
.1875	4.76
.1900	4.83	#10		24	32
.1969	5.00						5.00	*X	0.80	0.5, 0.75, 0.90
.2087	5.30
.2160	5.49	#12	24	28	32
.2165	5.50						5.50	***	0.90	0.5
.2188	5.56
.2362	6.00						6.00	*X	1.00	0.5, 0.75
.2500	6.35	1/4	20	28	32
.2756	7.00						7.00	***X	1.00	0.5, 0.75
.2812	7.14
.3125	7.94	5/16	18	24	32
.3125	7.94	1/16				27
.3150	8.00						8.00	*X	1.25	0.5, 0.75, 1
.3543	9.00						9.00	***X	1.25	0.75, 1
.3750	9.53	3/8	16	24	32						1
.3830	9.73
.3937	10.00						10.00	*X	1.5	0.75, 1, 1.25
.4050	10.29	1/8				27
.4331	11.00						11.00	***X	1.5	0.75, 1, 1.25
.4375	11.11	7/16	14	20	28
.4724	12.00						12.00	*X	1.75	1, 1.25, 1.5	1.5
.5000	12.70	1/2	13	20	28
.5180	13.16
.5400	13.72	1/4				18
.5512	14.00						14.00	**X	2.00	1, 1.25, 1.5
.5625	14.29	9/16	12	18	24
.6250
.6299	16.00						16.00	*X	2.00	1, 1.5	1.5
.6560	16.66
.6750	17.15	3/8				18
.6875	17.46	11/16			24
.7087	18.00						18.00	**X	2.5	1, 1.5, 2	1.5
.7500	19.05	3/4	10	16	20
.7874	20.00						20	*X	2.5	1, 1.5, 2	1.5
.8125	20.64	13/16			20
.8250	20.96
.8400	21.34	1/2				14
.8661	22.00						22	**X	2.5	1, 1.5, 2	1.5
.8750	22.23	7/8	9	14	20
.9020	22.91
.9375	23.81	15/16			20
.9449	24.00						24	*X	3	1, 1.5, 2
1.0000	25.40	1	8	14	20
1.0236	26.00						26	***X		1.5	1.5
1.0410	26.44
1.0500	26.67	3/4				14
1.0625	26.99	1-1/16			18
1.0630	27.00	27						**X	3	1, 1.5, 2
1.1250	28.58	1-1/8	7	12	18
1.1811	30.00						30	*X	3.5	1, 1.5, 2, 3
1.1875	30.16	1-3/16			18
1.1890	30.20
1.2500	31.75	1-1/4	7	12	18
1.2598	32.00						32	***X		1.5, 2
1.2992	33.00						33	**X	3.5	1.5, 2, 3
1.3090	33.25
1.3125	33.34	1-5/16			18
1.3150	33.40	1				11-1/2
1.3750	34.93	1-3/8	6	12	18
1.3780	35.00						35	***X		1.5
1.4173	36.00						36	*X	4	1.5, 2, 3
1.4375	36.51	1-7/16			18
1.4920	37.90									1.5
1.4961	38.00						38	***X
1.5000	38.10	1-1/2	6	12	18
1.5354	39.00						39	**X	4	1.5, 2, 3
1.5625	39.69	1-9/16			18
1.5748	40.00						40	***X		1.5, 2, 3
1.6250	41.28	1-5/8			18
1.6500	41.91
1.6535	42.00						42	*X	4.5	1.5, 2, 3, 4
1.6600	42.16	1-1/4				11-1/2
1.6875	42.86	1 11/16			18
1.7450	44.32

These guides are provided as a general reference. Always verify sizes, properties, and tolerances for your specific application.