FAQ

How to Measure Screws & Washers
Fastener Length
Measuring Diameter
Thread Pitch/Thread Count (TPI)
Nuts & Washers
Thread Specications
Standard / Imperial
Metric
Size
Bolt Diameter
Coarse (Threads per Inch)
Fine (Threads per Inch)
Bolt Diameter
Coarse (Threads per Inch)
Fine (Threads per Inch)
Bolt Diameter
Standard
Fine
Extra (Super) Fine
Screw Length
Countersunk Length
Oval Head Length
Diameter
Diameter
1/4" 5/16" 3/8" 7/16" 1/2" 9/16" 5/8" 3/4" 7/8" 1" 1-1/8" 1-1/4" 1-1/2"
20 18 16 14 13 12 11 10 9 8 7 7 6
28 24 24 20 20 18 18 16 14 12 12 12 12
#0000 #000 #00 #0 #1 #2 #3 #4 #5 #6 #8 #10 #12
64 56 48 40 40 32 32 24 24
160 120 90 80 72 64 56 48 44 40 36 32 28
M2 M2.5 M3 M4 M5 M6 M7 M8 M10 M12 M14 M16 M18 M20
.4 .45 .5 .7 .8 1.0 1.0 1.25 1.5 1.75 2.0 2.0 2.5 2.5
1.0 1.25 1.5 1.5
1.0 1.25
HOW TO SELECT YOUR PRODUCT . . .
FASTENERS
Typically, fastener length is measured from where the surface of the material will be when the fastener is completely installed to the end
of the fastener.
For instance, on fasteners where the head sits above the surface (i.e. pan head screw, hex bolts), it will be measure from under the head to the end
of the faster. Whereas fasteners that sit ush to the surface (i.e. at head screw) are measured from the top of the head to the end of the fastener.
The most common measure of a fastener diameter is the
thread diameter also known as major diameter. Shank
diameter is the diameter between the head and the threaded
portion of the bolt (S). The root diameter, also known as the
minor diamter, is the diameter of the bolt at the root or of the
external thread (R).
Thread count, also known as TPI, is only used with US fasteners and is the number of threads per inch measured along the length of the fastener.
Thread pitch is used in place of thread count for metric fasteners. Thread pitch is the distance between one thread and the next.
Both nuts & washers are sized by t. For example, a 3/4” washer ts a 3/4” bolt
Thread Diameter (T)
Shank Diameter (S)
Root Diameter (R)
S T
1”
US - Threads Per Inch (TPI) Metric - Thread pitch
1 2 3 4 5 6
R
S T R
S T
1”
US - Threads Per Inch (TPI) Metric - Thread pitch
1 2 3 4 5 6
R
S T R
S T
1”
US - Threads Per Inch (TPI) Metric - Thread pitch
1 2 3 4 5 6
R
S T R
Diameter