REF: Hex, Socket (Allen) and Torx Bolt and Screw Wrench Sizes


With the charts below and knowing or deducing the nut / bolt thread size, you can figure what size wrench is needed.
If you are not sure of the thread size, you can reference the Hardware P/N & Descriptions pages in the Sportsterpedia to find bolt sizes for IH and Evo Sportsters.
And likewise, if you know the wrench size, you can sometimes deduce the thread size (barring course or fine threading).

Measuring a Hex Bolt / Nut Size

Let's say you have a bolt / nut you need to remove but you don't know what size wrench to use.
First and foremost, use the appropriate wrench type (6 point hex requires a 6 point wrench).
Using a 12 point wrench on a 6 point hex will eventually result in either rounding the hex corners or stripping / breaking the wrench.
Likewise, if a 6 point wrench even fits on a 12 point nut / bolt, it will not be able to keep enough torque on the corners and will end up stripping them.

You can measure across two opposite flats of a hex bolt / nut with a tape measure or yard stick. But it will not be as accurate as using a caliper.
Either way, get the measurement and choose a wrench that falls in the nearest size up from the hex size.
Wrenches come in standard sizes and most, but not all, hex bolts / nuts are made with standard wrench sizes in mind.
The real trouble comes when companies use “special manufacturing Specs” (most likely so you'll have to buy their tool to fit the part).

In the pic below, an engine sprocket nut from a Buell XB crank was measured at .806“ (20.47mm). The next size up SAE wrench size is .8125” or 13/16“ (20.6375mm).

1)

Hex Bolt and Socket (Allen) Screw Wrench Sizes

US Hex Bolt and Socket (Allen) Screw Wrench Size Metric Hex Bolt and Socket (Allen) Screw Wrench Size
Nominal
Thread Diameter
Hex Bolt
Wrench Size
Hex Socket
Wrench Size
Nominal
Thread Diameter
Hex Bolt
Wrench Size
Hex Socket
Wrench Size
#6 1/4” - M4 7mm 3mm
#8 1/4“ - M5 8mm 4mm
#10 5/16” - M6 10mm 5mm
#12 5/16“ - M8 13mm 6mm
1/4” 7/16“ 3/16” M10 17mm 8mm
5/16“ 1/2” 1/4“ M12 19mm 10mm
3/8” 9/16“ 5/16” M14 22mm 12mm
7/16“ 5/8” 3/8“ M16 24mm 14mm
1/2” 3/4“ 3/8” M18 27mm 14mm
9/16“ 1-3/16” 7/16“ M20 30mm 17mm
5/8” 1-5/16“ 1/2” M22 32mm 17mm
3/4“ 1-1/8” 5/8“ M24 36mm 19mm
7/8” 1-5/16“ 3/4” M30 46mm 22mm
1“ 1-1/2” 3/4“
1-1/8” 1-11/16“ 7/8”
1-1/4“ 1-7/8” 7/8“
1-3/8” 2-1/16“ 1”
1- 1/2“ 2-1/4” 1“
1-3/4” 2-5/8“ 1-1/4”
2“ 3” 1-1/2

Torx Screw Wrench Sizes

Screw
Size
Torx Socket
Set Screw
Torx Socket
Cap Screw
Torx Pan
Head Screw
Torx Flat
Head Screw
Torx Fillister
Head Screw
Torx Truss
Head Screw
Torx Oval
Head Screw
Torx Hex
Head Screw
Torx Internal
Washer Head
Screw
#2 T3 - T7 T6 - - - - T7
#3 T5 - T8 T7 - - - - T8
#4 T6 T10 T9 T8 T9 - - T9 T9
#5 T7 T10 T10 T9 T10 - T10 T10 T10
#6 T7 T15 T15 T10 T15 T10 T15 T15 T15
#8 T8 T25 T20 T15 T20 T15 T20 T20 T20
#10 T10 T27 T25 T20 T25 T20 T25 T25 T25
#12 T10 T27 T27 T25 T27 T25 T27 T27 T27
1/4“ T20 T30 T30 T27 T30 T27 T30 T30 T30
5/16” T27 T45 - T40 T40 T30 T40 T40 -
3/8“ T30 T50 T45 T40 T45 T40 T45 T45 -
7/16” T40 T55 T50 T50 T50 T45 T50 - -
1/2“ T45 T55 T55 T55 T55 T50 T50 - -

SAE to Metric Hex Wrench Conversions

When you reference the hex wrench chart below, be aware that using a larger size wrench will increase the chances of stripping the bolt head corners. In some cases, you may want to try using a size above the one recommended in the chart to see if it fits by chance. Not every metric size has a perfect SAE counterpart and vice-versa. There is no perfect substitute for the right size tool.

SAE Hex
Wrench Size
5/16”3/8“7/16”1/2“9/16”5/8“3/4”13/16“7/8”15/16“
SAE
Bolt Size
1/8”3/16“1/4”5/16“3/8”7/16“1/2”9/16“9/16”5/8“
Metric Hex
Wrench Size
8mm10mm11mm13mm14mm16mm19mm21mm22mm24mm

SAE to Metric Hex Key (Allen Head) Conversions

When you reference the hex key chart below, be aware that using a smaller size bit will increase the chances of stripping the corners. 2) In some cases, you may want to try using a size above the one recommended in the chart to see if it fits by chance. Not every metric size has a perfect SAE counterpart and vice-versa. There is no perfect substitute for the right size tool.

SAE Hex Key5/64”3/32“7/64”1/8“5/32”3/16“7/32”1/4“5/16”3/8“
Metric Hex Key2mm2-1/2mm3mm3-1/2mm4mm5mm6mm7mm8mm10mm



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