#2 screw dimensions and bolt sizes are commonly used for consumer electronics, household appliances, and small mechanical assemblies. This size features a 0.086″ nominal major diameter and is available in #2-56 coarse (UNC) or #2-64 fine (UNF), representing 56 and 64 threads per inch (TPI) respectively. This reference chart follows ANSI/ASME B18.6.3 and B18.3 standards for the head size and ANSI/ASME B1.1 standards for the thread dimensions to ensure compatibility across imperial fastening applications.
Disclaimer: Dimensions and tolerances may vary slightly depending on head style, manufacturer, or material — always verify with the official product datasheet before use.
#2-56 UNC Screw & Bolt – ANSI/ASME B1.1
Dimension
Size (in)
Min
Max
Major Diameter
0.0813
0.0854
Pitch Diameter
0.0717
0.0738
Minor Diameter
Not specified
0.0641
Threads Per Inch (TPI)
56
Major Diameter
0.0819
0.086
Pitch Diameter
0.0728
0.0744
Minor Diameter
Not specified
0.0647
Threads Per Inch (TPI)
56
#2-64 UNF Screw & Bolt – ANSI/ASME B1.1
Dimension
Size (in)
Min
Max
Major Diameter
0.0816
0.0854
Pitch Diameter
0.0733
0.0753
Minor Diameter
Not specified
0.0668
Threads Per Inch (TPI)
64
Major Diameter
0.0822
0.086
Pitch Diameter
0.0744
0.0759
Minor Diameter
Not specified
0.0674
Threads Per Inch (TPI)
64
Major Diameter –
The largest diameter of the external thread, measured crest to crest.
This defines the nominal size of the screw or bolt.
Pitch Diameter –
The diameter of an imaginary cylinder where the thread thickness equals
the space between threads. This dimension primarily controls thread fit
and tolerance class of 2A and 3A.
Minor Diameter –
The smallest diameter of the external thread, measured root to root.
This affects thread strength and clearance.
Threads Per Inch (TPI) –
The number of complete threads within one inch of thread length.
Higher TPI values indicate a finer thread pitch.
What is the tap drill size for #2-56 and #2-64 bolt or screw?
For aluminum, brass, or plastic (75% thread), a #50 (0.070″) drill bit is used for both thread types. For steel, stainless, or iron (50% thread), a #49 (0.073″) drill bit is recommended for #2-56 and a #48 (0.076″) drill bit for #2-64.
What clearance hole size is needed for a #2 bolt or screw?
For a Close Fit, a #43 (0.089″) drill bit is utilized. A #41 (0.096″) drill bit is used for a Free Fit.
What is the equivalent size for #2 in metric?
For size #2, the nearest metric match is M2.2.
This particular size has a maximum major diameter of 2.182 mm (0.08591 inch),
which means the measurement offset is only about 0.002 mm (9.0E-5 inch).
While these diameters are nearly identical, metric and imperial fasteners are not interchangeable. They utilize fundamentally different thread systems: Imperial fasteners are measured by Threads Per Inch (TPI), whereas metric fasteners use Thread Pitch. Mixing metric and imperial hardware is strongly discouraged, as it can lead to damaged components, reduced load-bearing capacity, and catastrophic mechanical failure.
What is the difference between a bolt and a screw?
The difference is based on the intent of the fastener’s use; If the primary intent is for the fastener to pass through an unthreaded holes and be assembled with a nut, it is a Bolt. In this application, you usually hold the head and turn the nut to apply tension. But if the primary intent is for the fastener to be installed into a threaded (tapped) hole, it is a Screw. In this application, the connection is tightened by turning the head of the fastener itself.
