Grayforge Construction Logs
(No Project Selected)
Project Selection:
Choose a project to view
James' Glasair III Build
James' Zenith CH750-SD Build
Russ' RV-7A
Drill Bit Size Chart to 1/4 inch Diameter
Legend:
Number Drill
Fractional Inch
Letter Drill
Millimeters
Millimeters
Inches
Designation
Tap Drill/Pilot Drill Uses
.3429mm
.0135"
#80
.3683mm
.0145"
#79
.3969mm
.015625"
1/64"
#0 Pilot
.4064mm
.016"
#78
.4572mm
.018"
#77
.5mm
.0197"
.508mm
.02"
#76
.5334mm
.021"
#75
.5715mm
.0225"
#74
.6096mm
.024"
#73
.635mm
.025"
#72
.6604mm
.026"
#71
.7112mm
.028"
#70
.74168mm
.0292"
#69
.75mm
.0295"
M1x.25 coarse
.7874mm
.031"
#68
.7938mm
.03125"
1/32"
#0 Pilot
.8128mm
.032"
#67
.8382mm
.033"
#66
.85mm
.0335"
M1.1x.25 coarse
.889mm
.035"
#65
.9144mm
.036"
#64
.9398mm
.037"
#63
.95mm
.0374"
M1.2x.25 coarse
.9652mm
.038"
#62
.9906mm
.039"
#61
1mm
.0394"
1.016mm
.04"
#60
1.0414mm
.041"
#59
1.0668mm
.042"
#58
1.0922mm
.043"
#57
1.1mm
.0433"
M1.4x.3 coarse
1.1811mm
.0465"
#56
1.1906mm
.046875"
3/64"
#0-80 UNF
1.25mm
.0492"
M1.6x.35 coarse
1.3mm
.0512"
M1.7x.35 coarse
1.3208mm
.052"
#55
1.397mm
.055"
#54
1.45mm
.0571"
M1.8x.35 coarse
1.5mm
.0591"
1.5113mm
.0595"
#53
#1-64 UNC, #1-72 UNF
1.5875mm
.0625"
1/16"
1.6mm
.063"
M2x.4 coarse
1.6129mm
.0635"
#52
1.7018mm
.067"
#51
1.75mm
.0689"
M2.2x.45 coarse
1.778mm
.07"
#50
#2-64 UNF, #2-56 UNC
1.8542mm
.073"
#49
1.9304mm
.076"
#48
1.9844mm
.078125"
5/64"
1.9939mm
.0785"
#47
#3-48 UNC
2mm
.0787"
2.05mm
.0807"
M2.5x.45 coarse
2.0574mm
.081"
#46
2.0828mm
.082"
#45
#3-56 UNF
2.1844mm
.086"
#44
2.2606mm
.089"
#43
#4-40 UNC
2.3749mm
.0935"
#42
#4-48 UNF
2.3813mm
.09375"
3/32"
2.4384mm
.096"
#41
2.4892mm
.098"
#40
2.5mm
.0984"
M3x.5 coarse
2.5273mm
.0995"
#39
2.5781mm
.1015"
#38
#5-40 UNC
2.6416mm
.104"
#37
#5-44 UNF
Millimeters
Inches
Designation
Tap Drill/Pilot Drill Uses
2.7051mm
.1065"
#36
#6-32 UNC
2.7781mm
.109375"
7/64"
2.794mm
.11"
#35
2.8194mm
.111"
#34
2.8702mm
.113"
#33
#6-40 UNF
2.9mm
.1142"
M3.5x.6 coarse
2.9464mm
.116"
#32
3mm
.1181"
3.048mm
.12"
#31
3.175mm
.125"
1/8"
3.2639mm
.1285"
#30
3.3mm
.1299"
M4x.7 coarse
3.4544mm
.136"
#29
#8-32 UNC, #8-36 UNF
3.5mm
.1378"
M4x.5 Fine
3.5687mm
.1405"
#28
#6 Screw
3.5719mm
.140625"
9/64"
3.6mm
.1417"
M4x.35 Fine
3.6576mm
.144"
#27
3.7mm
.1457"
M4.5x.75 coarse
3.7338mm
.147"
#26
3.7973mm
.1495"
#25
#10-24 UNC
3.8608mm
.152"
#24
3.9116mm
.154"
#23
3.9688mm
.15625"
5/32"
3.9878mm
.157"
#22
4mm
.1575"
4.0386mm
.159"
#21
#10-32 UNF
4.0894mm
.161"
#20
4.2mm
.1654"
M5x.8 coarse
4.2164mm
.166"
#19
#8 Screw
4.3053mm
.1695"
#18
4.3656mm
.171875"
11/64"
4.3942mm
.173"
#17
#12-24 UNC
4.4958mm
.177"
#16
4.5mm
.1772"
M5x.5 Fine
4.572mm
.18"
#15
#12-28 UNF
4.6228mm
.182"
#14
4.699mm
.185"
#13
4.7625mm
.1875"
3/16"
4.8006mm
.189"
#12
AN3 Bolt
4.8514mm
.191"
#11
4.9149mm
.1935"
#10
4.9784mm
.196"
# 9
5mm
.1969"
M6x1 coarse
5.0546mm
.199"
# 8
5.1054mm
.201"
# 7
1/4"-20 UNC
5.1594mm
.203125"
13/64"
5.1816mm
.204"
# 6
5.2197mm
.2055"
# 5
5.25mm
.2067"
M6x.75 Fine
5.3086mm
.209"
# 4
5.4102mm
.213"
# 3
1/4"-28 UNF
5.5mm
.2165"
M6x.5 Fine
5.5563mm
.21875"
7/32"
5.6134mm
.221"
# 2
5.7912mm
.228"
# 1
5.9436mm
.234"
A
5.9531mm
.234375"
15/64"
6mm
.2362"
M7x1 coarse
6.0452mm
.238"
B
6.1468mm
.242"
C
6.2484mm
.246"
D
1/16"-27 NPT
6.25mm
.2461"
M7x.75 Fine
6.35mm
.25"
1/4", E
AN4 Bolt
7.9375mm
.3125"
5/16"
3/8"-16 UNC, AN5 Bolt
When using a drill bit for a feeler gauge, please remember that many drill bits are actually undersize at the
shank end of the drill bit so please use the above bit sizes with a grain of salt!
Also note that to correct for a broad feeler gauge or a loose-fitting drill bit:
ROC = (D2 -W2 ) /8T
Where:
W = the width of the feeler gauge, or if the drill bit can be moved back and forth under the straight edge by the total amount W
D = mirror diameter,
T = gauge thickness or bit diameter.