FASTENERS 101™
Fastener Reference Tables

Conversions, Hardness, Thread Pitch, Tensile Strength

The tables below are provided as a general guide to help you better understand metric and imperial measurements. Always refer to project specifications and consult an engineer to ensure that your application is appropriate.

Printable Conversion Charts and Quick Reference Sheets

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

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

CLASS 5.8 -- 520 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


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 Chart

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 and 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
72 .0560 53 .0595 52 .0635        
2 56 .0860 .0641 50 .0700 49 .0730 43 .0890 41 .0960
64 .0668 50 .0700 48 .0760        
3 48 .0900 .0734 47 .0785 44 .0860 37 .1040 35 .1100
56 .0771 45 .0820 43 .0890        
4 40 1120 .0813 43 .0890 41 .0960 32 .1160 30 .1285
48 .0864 42 .0935 40 .0980        
5 40 1250 .0943 38 .1015 7/64 .1094 30 .1285 29 .1360
44 .0971 37 .1040 35 .1100        
6 32 .1380 .0997 36 .1065 32 .1160 27 .1440 25 .1495
40 .1073 33 .1130 31 .1200        
8 32 .1640 .1257 29 .1360 27 .1440 18 .1695 16 .1770
36 .1299 29 .1360 26 .1470        
10 24 1900 .1389 25 .1495 20 .1610 9 .1960 7 .2010
32 .1517 21 .1590 18 .1695        
12 24 0.216 .1649 16 .1770 12 .1890 2 .2210 1 .2280
28 .1722 14 .1820 10 .1935
32 .1777 13 .1850 9 .1960
1/4 20 0.2500 .1887 7 .2010 7/32 .2188 F .2570 H .2260
28 .2062 3 .2130 1 .2280
32 .2117 7/32 .2188 1 .2280
5/16 18 0.313 .2443 F .2570 J .2770 P .3230 Q .3320
24 .2614 I .2720 9/32 .2812
32 .2742 9/32 .2812 L .2900
3/8 16 .3750 .2983 5/16 .3125 Q .3320 W .3860 X .3970
24 .3239 Q .3320 S 3480
32 .3367 11/32 .3438 T .3580
7/16 14 0.438 .3499 U .3680 25/64 .3906 29/64 .4531 15/32 .4687
20 .3762 25/64 .3906 13/32 .4062
28 .3937 Y .4040 Z .4130
1/2 13 0.500 .4056 27/64 .4219 29/64 .4531 33/64 .5156 17/32 .5312
20 .4387 29/64 .4531 15/32 .4688
28 .4562 15/32 .4688 15/32 .4688
9/16 12 .5625 .4603 31/64 .4844 33/64 .5156 37/64 .5781 19/32 .5938
18 .4943 33/64 .5156 17/32 .5312
24 .5514 33/64 .5156 17/32 .5312
5/8 11 0.625 .5135 17/32 .5312 9/16 .5625 41/64 .6406 21/32 .6562
18 .5568 37/64 .5781 19/32 .5938
24 .5739 37/64 .5781 19/32 .5938
11/16 24 .5875 .6364 41/64 .6406 21/32 .6562 45/64 .7031 23/32 .7188
3/4 10 0.75 .6273 21/32 .6562 11/16 .6875 49/64 .7656 25/32 .7812
16 .6733 11/16 .6875 45/64 .7031
20 .6887 45/64 .7031 23/32 .7188
13/16 20 .8125 .7512 49/64 .7656 25/32 .7812 53/64 .8281 27/32 .8438
7/8 9 0.875 .7387 49/64 .7656 51/64 .7969 57/64 .8906 29/32 .9062
14 .7874 13/16 .8125 53/64 .8281
20 .8137 53/64 .8281 27/32 .8438
15/16 20 .9375 .8762 57/64 .8906 29/32 .9062 61/64 .9531 31/32 .9688
1 8 1 .8466 7/8 .8750 59/64 .9219 1-1/64 1.0156 1-1/32 1.0313
12 .8978 15/16 .9375 61/64 .9531
20 .9387 61/64 .9531 31/32 .9688
1-1/16 18 1.0625 .9943 1.000 1.000 1-1/64 1.1056 1-5/64 1.0781 1-3/32 1.0938
1-1/8 7 1.125 .9497 63/64 .9844 1-1/32 1.0313 1-9/64 1.1406 1-5/32 1.1562
12 1.0228 1-3/64 1.0469 1-5/64 1.0781
18 1.0568 1-1/16 1.0625 1-5/64 1.0781
1-3/16 18 1.1875 1.1193 1-1/8 1.1250 1-9/64 1.1406 1-13/64 1.2031 1-7/32 1.2188

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