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Pilot Hole Size Chart

Type AB Self-Tapping Screws, Type B Self-Tapping Screws, Type 25 Thread Cutting Screws. (All require the same pilot hole and drill bit sizes.)

Screw Size Screw Threads per Inch Recommended Hole Diameter Drill Bit Size
#2 32 0.0760" #48
#3 28 0.0810" #46
#4 24 0.0860" #44
#5 20 0.1065" #36
#6 20 0.1160" #32
#7 19 0.1285" #30
#8 18 0.1360" #29
#10 16 0.1590" #21
#12 24 0.1875" 3/16"
1/4" 14 0.2188" 7/32"
5/16" 12 0.2720" I
3/8" 12 0.3281" 21/64"

Type A Self-Tapping Screws

Screw Size Screw Threads per Inch Recommended Hole Diameter Drill Bit Size
#2 32 0.0760" #48
#3 28 0.0810" #46
#4 24 0.0860" #44
#5 20 0.1065" #36
#6 18 0.1160" #32
#7 16 0.1285" #30
#8 15 0.1360" #29
#10 12 0.1590" #21
#12 11 0.1875" 3/16"
#14 / 1/4" 10 0.2188" 7/32"
5/16" 9 0.2900" L
3/8" 9 0.3438" 11/32"

Type F, Type 1, Type 23 Thread Cutting Screws

Screw Size-TPI Recommended Hole Diameter Drill Bit Size
2-56 0.0730" #49
3-48 0.0810 #46
4-40 0.0960" #41
5-40 0.1010" #37
6-32 0.1200" #31
8-32 0.1470" #26
10-24 0.1730" #17
10-32 0.1770" #16
12-24 0.1990" #8
1/4-20 0.2280" #1
5/16-18 0.2900" L
3/8-16 0.3580" T
1/2-13 0.4531" 29/64"

High Low Thread Forming Screws

Screw Size Threads Per Inch Recommended Hole Diameter for Material with Flexural Modulus of Up to 200,000 P.S.I. Drill Bit Size Recommended Hole Diameter for Material with Flexural Modulus of Over to 200,000 P.S.I. Drill Bit Size
#2 32 0.067" #51 0.070" #50
#3 28 0.073" #49 0.078" 5/64"
#4 24 0.081" #46 0.086" #44
#5 20 0.094" #42 0.100" #39
#6 19 0.102" #38 0.110" #35
#7 19 0.120" #31 0.125" 1/8"
#8 18 0.120" #31 0.129" #30
#10 16 0.136" #29 0.144" #27
#12 16 0.157" #22 0.166" #19
#14 / 1/4" 15 0.189" #12 0.201" #7
5/16" 14 0.238" #B 0.250" 1/4" (E)

U-Drive or Hammer Drive Screws

Screw Size-TPI Recommended Hole Diameter Drill Bit Size
00 0.052" #55
0 0.067" #51
2 0.086" #44
4 0.104" #37
6 0.120" #31
7 0.136" #29
8 0.144" #27
10 0.161" #20
12 0.191" #11
14 0.221" #2

Thread Forming Screws for Plastics

Screw Size Screw Threads Per Inch Soft Ductile Materials Brittle Materials
#0 40 0.0498" 0.0490"
#2 28 0.0760" 0.0800"
#3 24 0.0880" 0.0940"
#4 20 0.1000" 0.1060"
#5 20 0.1110" 0.1170"
#6 19 0.1220" 0.1280"
#7 18 0.1340" 0.1420"
#8 16 0.1490" 0.1580"
#9 15 0.1620" 0.1720"
#10 14 0.1750" 0.1850"
#12 11 0.1950" 0.2050"
#14 or 1/4" 10 0.2240" 0.2400"
5/16" 9 0.2860" 0.3030"

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