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Screw Threads

Contents

Screw Threads

A 82° flat head except the head is undercut to 70% of its normal side height.
Often standard for short lengths because it allows for greater length of threads.
Flat-head undercut screws also fit standard counterbored holes and does a great job when using thin stock.

Screw slots

Straight blade screw drivers that fit are hard to find.

Screw
Size
Metric
Slot Width (mm)
Min
 Max
M2
 0.5
 0.7
M2.5
 0.6
 0.8
M3
 0.8
 1.0
M3.5
 1.0
 1.2
M4
 1.2
 1.5
M5
 1.2
 1.5
M6
 1.6
 1.9
M8
 2.0
 2.3
M10
 2.5
 2.8


Screw
Size
Inch
Depriciated
Slot Width (mills)
Min
 Max
#2
 23
 31
#3
 27
 35
#4
 31
 39
#5
 35
 43
#6
 39
 48
#8
 45
 54
#10
 50
 60
#12
 56
 67
1/4 (.250)
 64
 75
5/16 (.3125)
 72
 84
3/8 (.375)
 81
 94

Metric ISO Threads

Size Pitch (mm) Tapping Diameter (mm) Clearance Holes (mm)

Coarse Fine Coarse Fine Close Medium Coarse
M1.6 0.35
1.25
1.7 1.8 2.0
M2 0.4
1.6
2.2 2.4 2.6
M2.5 0.45
2.05
2.7 2.9 3.1
M3 0.5
2.5
3.2 3.4 3.6
M4 0.7
3.3
4.3 4.5 4.8
M5 0.8
4.2
5.3 5.5 5.8
M6 1.0
5.0
6.4 6.6 7.0
M8 1.25 1.0 6.8 7.0 8.4 9.0 10.0
M10 1.5 1.25 8.5 8.7 10.5 11.0 12.0
M12 1.75 1.25 10.2 10.8 13 14 15
M16 2.0 1.5 14.0 14.5 17.0 18.0 19.0
M20 2.5 1.5 17.5 18.5 21.0 22.0 24.0
M24 3.0 2.0 21.0 22.0 25.0 26.0 28.0
M30 3.5 2.0 26.5 28.0 31.0 33.0 35.0
M36 4.0 3.0 32.0 33.0 37.0 39.0 42.0



Strength vs Torque

Floody-dust

Camera mount thread is 1/4"-20

Legacy data

tap size
(major dia. - threads / inch)		 screw
major dia.		 tap drill size
for 75% .dia		 tap drill size
for 50% .dia		 clearance drill Metric update
approx replacement
#0-80 0.060 3/64 (.0469) 55 (.0520) 50 (.0700)
#1-64 0.073 53 (.0595) 1/16 (.0625) 46 (.0810)
#2-56 0.086 50 (.0700) 49 (.0730) 41 (.0960)
#3-48 0.099 47 (.0785) 44 (.0860) 35 (.1100)
#4-40 0.112 43 (.0890) 41 (.0960) 30 (.1285) M3x0.5
#5-40 0.125 38 (.1015) 7/64 (.1094) 29 (.1360)
#6-32 0.138 36 (.1065) 32 (.1160) 25 (.1495)
#8-32 0.164 29 (.1360) 27 (.1440) 16 (.1770)
#10-24 0.190 25 (.1495) 20 (.1610) 7 (.2010) 5mm
#12-24 0.216 16 (.1770) 12 (.1890) 1 (.2280)
1/4-20 .2500 7 (.2010) 7/32 (.2188) H (.2660)
5/16-18 .3125 F (.2570) J (.2770) Q (.3320)
3/8-16 .3750 5/16 (.3125) Q (.3320) X (.3970)
7/16-14 .4375 U (.3680) 25/64 (.3906) 15/32 (.4687)
1/2-13 .5000 27/64 (.4219) 29/64 (.4531) 17/32 (.5312)
9/16-12 .5625 31/64 (.4844) 33/64 (.5156) 19/32 (.5938)
5/8-11 .6250 17/32 (.5312) 9/16 (.5625) 21/32 (.6562)
3/4-10 .7500 21/32 (.6562) 11/16 (.6875) 25/32 (.7812)
7/8-9 .8750 49/64 (.7656) 51/64 (.7969) 29/32 (.9062)
1"-8 1.000 7/8 (.8750) 59/64 (.9219) 1-1/32 (1.0313)
1 1/8-7 1.1250 63/64 (.9844) 1-1/32 (1.0313) 1-5/32 (1.1562)


Legacy Fine Threads

tap size
(major dia. - threads / inch)		 screw
major dia.		 tap drill size
for 75% .dia		 tap drill size
for 50% .dia		 clearance drill
#1-72 0.073 53 (.0595) 52 (.0635) 46 (.0810)
#2-64 0.086 50 (.0700) 48 (.0760) 41 (.0960)
#3-56 0.099 45 (.0820) 43 (.0890) 35 (.1100)
#4-48 0.112 42 (.0935) 40 (.0980) 30 (.1285)
#5-44 0.125 37 (.1040) 35 (.1100) 29 (.1360)
#6-40 0.138 33 (.1130) 31 (.1200) 25 (.1495)
#8-36 0.164 29 (.1360) 26 (.1470) 16 (.1770)
#10-32 0.190 21 (.1590) 18 (.1695) 7 (.2010)
#12-28 0.216 14 (.1820) 10 (.1935) 1 (.2280)
1/4-28 .2500 3 (.2130) 1 (.2280) H (.2660)
5/16-24 .3125 I (.2720) 9/32 (.2812) Q (.3320)
3/8-24 .3750 Q (.3320) S (.3480) X (.3970)
7/16-20 .4375 25/64 (.3906) 13/32 (.4062) 15/32 (.4687)
1/2-20 .5000 29/64 (.4531) 15/32 (.4688) 17/32 (.5312)
9/16-18 .5625 33/64 (.5156) 17/32 (.5312) 19/32 (.5938)
5/8-18 .6250 37/64 (.5781) 19/32 (.5938) 21/32 (.6562)
3/4-16 .7500 11/16 (.6875) 45/64 (.7031) 25/32 (.7812)
7/8-14 .8750 13/16 (.8125) 53/64 (.8281) 29/32 (.9062)
1"-12 1.000 15/16 (.9375) 61/64 (.9531) 1-1/32 (1.0313)
1 1/8-12 1.1250 1-3/64 (1.0469) 1-5/64 (1.0781) 1-5/32 (1.1562)

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