#12 screw dimensions and bolt sizes are usually used for heavy-duty construction, specialized mechanical assemblies, and industrial equipment. This size have a 0.216″ nominal major diameter and is available in #12-24 coarse (UNC), #12-28 fine (UNF), or #12-32 extra-fine (UNEF) thread pitches, representing 24, 28, and 32 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.
#12-24 UNC Screw & Bolt – ANSI/ASME B1.1
Dimension
Size (in)
Min
Max
Major Diameter
0.2078
0.215
Pitch Diameter
0.1845
0.1879
Minor Diameter
Not specified
0.1654
Threads Per Inch (TPI)
24
Major Diameter
0.2088
0.216
Pitch Diameter
0.1863
0.1889
Minor Diameter
Not specified
0.1664
Threads Per Inch (TPI)
24
#12-28 UNF Screw & Bolt – ANSI/ASME B1.1
Dimension
Size (in)
Min
Max
Major Diameter
0.2085
0.215
Pitch Diameter
0.1886
0.1918
Minor Diameter
Not specified
0.1725
Threads Per Inch (TPI)
28
Major Diameter
0.2095
0.216
Pitch Diameter
0.1904
0.1928
Minor Diameter
Not specified
0.1735
Threads Per Inch (TPI)
28
#12-32 UNEF Screw & Bolt – ANSI/ASME B1.1
Dimension
Size (in)
Min
Max
Major Diameter
0.209
0.215
Pitch Diameter
0.1915
0.1947
Minor Diameter
Not specified
0.1778
Threads Per Inch (TPI)
32
Major Diameter
0.21
0.216
Pitch Diameter
0.1933
0.1957
Minor Diameter
Not specified
0.1788
Threads Per Inch (TPI)
32
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 #12-24, #12-28, and #12-32 screws or bolts?
The appropriate tap drill depends on the material and required thread engagement. For aluminum, brass, or plastic (75% thread), a #16 (0.177″) drill bit is specified for #12-24, a #14 (0.182″) for #12-28, and a #13 (0.185″) for #12-32. For steel, stainless, or iron (50% thread), a #12 (0.189″) drill bit is recommended for #12-24, a #10 (0.194″) for #12-28, and a #9 (0.196″) for #12-32.
What clearance hole size is needed for a #12 bolt or screw?
For a Close Fit, a #2 (0.221″) drill bit is utilized. For a Normal/Free Fit (standard clearance), a #1 (0.228″) drill bit is specified.
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.
