2-1/4” Bolt & Screw Dimensions: Diameter & Head Size
2-1/4″ bolt dimensions and screw sizes are specialized for heavy-duty marine propulsion, large-scale industrial presses, and massive structural bridge components. This size have a 2.250″ nominal major diameter and is available in 2-1/4″-4.5 coarse (UNC) thread pitch, representing 4.5 threads per inch (TPI). 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 extra-large 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.
2-1/4-4.5 UNC Screw & Bolt – ANSI/ASME B1.1
Dimension
Size (in)
Min
Max
Major Diameter
2.2141
2.2471
Pitch Diameter
2.0882
2.1028
Minor Diameter
Not specified
1.9825
Threads Per Inch (TPI)
4.5
Major Diameter
2.2251
2.2471
Pitch Diameter
2.0931
2.1028
Minor Diameter
Not specified
1.9825
Threads Per Inch (TPI)
4.5
Major Diameter
2.228
2.25
Pitch Diameter
2.0984
2.1057
Minor Diameter
Not specified
1.9854
Threads Per Inch (TPI)
4.5
2-1/4-6 UN Screw & Bolt – ANSI/ASME B1.1
Dimension
Size (in)
Min
Max
Major Diameter
2.2292
2.2474
Pitch Diameter
2.1303
2.1391
Minor Diameter
Not specified
2.0489
Threads Per Inch (TPI)
6
Major Diameter
2.2318
2.25
Pitch Diameter
2.1351
2.1417
Minor Diameter
Not specified
2.0515
Threads Per Inch (TPI)
6
2-1/4-8 UN Screw & Bolt – ANSI/ASME B1.1
Dimension
Size (in)
Min
Max
Major Diameter
2.2326
2.2476
Pitch Diameter
2.1584
2.1664
Minor Diameter
Not specified
2.0988
Threads Per Inch (TPI)
8
Major Diameter
2.235
2.25
Pitch Diameter
2.1628
2.1688
Minor Diameter
Not specified
2.1012
Threads Per Inch (TPI)
8
2-1/4-12 UN Screw & Bolt – ANSI/ASME B1.1
Dimension
Size (in)
Min
Max
Major Diameter
2.2368
2.2482
Pitch Diameter
2.188
2.1941
Minor Diameter
Not specified
2.149
Threads Per Inch (TPI)
12
Major Diameter
2.2386
2.25
Pitch Diameter
2.1913
2.1959
Minor Diameter
Not specified
2.1508
Threads Per Inch (TPI)
12
2-1/4-16 UN Screw & Bolt – ANSI/ASME B1.1
Dimension
Size (in)
Min
Max
Major Diameter
2.239
2.2484
Pitch Diameter
2.2023
2.2078
Minor Diameter
Not specified
2.174
Threads Per Inch (TPI)
16
Major Diameter
2.2406
2.25
Pitch Diameter
2.2053
2.2094
Minor Diameter
Not specified
2.1756
Threads Per Inch (TPI)
16
2-1/4-20 UN Screw & Bolt – ANSI/ASME B1.1
Dimension
Size (in)
Min
Max
Major Diameter
2.2404
2.2485
Pitch Diameter
2.211
2.216
Minor Diameter
Not specified
2.189
Threads Per Inch (TPI)
20
Major Diameter
2.2419
2.25
Pitch Diameter
2.2137
2.2175
Minor Diameter
Not specified
2.1905
Threads Per Inch (TPI)
20
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 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.
