3/4” Bolt & Screw Dimensions: Diameter & Head Size

3/4″ bolt dimensions and screw sizes are mostly used for heavy structural engineering, industrial equipment mounting, and high-load mechanical assemblies. This size is standardized with a 0.750″ nominal major diameter and is available in 3/4″-10 coarse (UNC), 3/4″-16 fine (UNF), or 3/4″-20 extra-fine (UNEF) thread pitches, representing 10, 16, and 20 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.

Thread diagram fot bolt and screw depicting the major diameter, minor diameter, pitch diameter, and threads per inch
Hex head diagram
Cap head diagram
Low-cap head diagram
Button head diagram
Flat head diagram
Pan head diagram
3/4-10 UNC Screw & Bolt – ANSI/ASME B1.1
Dimension Size (in)
Min Max
Major Diameter 0.7288 0.7482
Pitch Diameter 0.6744 0.6832
Minor Diameter Not specified 0.6291
Threads Per Inch (TPI) 10
Major Diameter 0.7353 0.7482
Pitch Diameter 0.6773 0.6832
Minor Diameter Not specified 0.6291
Threads Per Inch (TPI) 10
Major Diameter 0.7371 0.75
Pitch Diameter 0.6806 0.685
Minor Diameter Not specified 0.6309
Threads Per Inch (TPI) 10
3/4-12 UN Screw & Bolt – ANSI/ASME B1.1
Dimension Size (in)
Min Max
Major Diameter 0.7369 0.7483
Pitch Diameter 0.6887 0.6942
Minor Diameter Not specified 0.6491
Threads Per Inch (TPI) 12
Major Diameter 0.7386 0.75
Pitch Diameter 0.6918 0.6959
Minor Diameter Not specified 0.6508
Threads Per Inch (TPI) 12
3/4-16 UNF Screw & Bolt – ANSI/ASME B1.1
Dimension Size (in)
Min Max
Major Diameter 0.7343 0.7485
Pitch Diameter 0.7004 0.7079
Minor Diameter Not specified 0.6741
Threads Per Inch (TPI) 16
Major Diameter 0.7391 0.7485
Pitch Diameter 0.7029 0.7079
Minor Diameter Not specified 0.6741
Threads Per Inch (TPI) 16
Major Diameter 0.7406 0.75
Pitch Diameter 0.7056 0.7094
Minor Diameter Not specified 0.6756
Threads Per Inch (TPI) 16
3/4-20 UNEF Screw & Bolt – ANSI/ASME B1.1
Dimension Size (in)
Min Max
Major Diameter 0.7406 0.7487
Pitch Diameter 0.7118 0.7162
Minor Diameter Not specified 0.6892
Threads Per Inch (TPI) 20
Major Diameter 0.7419 0.75
Pitch Diameter 0.7142 0.7175
Minor Diameter Not specified 0.6905
Threads Per Inch (TPI) 20
3/4-28 UN Screw & Bolt – ANSI/ASME B1.1
Dimension Size (in)
Min Max
Major Diameter 0.7423 0.7488
Pitch Diameter 0.7218 0.7256
Minor Diameter Not specified 0.7063
Threads Per Inch (TPI) 28
Major Diameter 0.7435 0.75
Pitch Diameter 0.7239 0.7268
Minor Diameter Not specified 0.7075
Threads Per Inch (TPI) 28
3/4-32 UN Screw & Bolt – ANSI/ASME B1.1
Dimension Size (in)
Min Max
Major Diameter 0.7429 0.7489
Pitch Diameter 0.725 0.7286
Minor Diameter Not specified 0.7117
Threads Per Inch (TPI) 32
Major Diameter 0.744 0.75
Pitch Diameter 0.727 0.7297
Minor Diameter Not specified 0.7128
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.
Hex Head – ANSI/ASME B18.2.1
Dimension Size (in)
MinMax
Width Across Flats 1.088 1.125
Width Across Corners 1.24 1.299
Head Height 0.455 0.524
Hex Socket Cap Head – ANSI/ASME B18.3
Dimension Size (in)
MinMax
Head Diameter 1.094 1.125
Head Height 0.74 0.75
Hex Socket Size 5/8 (0.625 in)
Hex Socket Button Head – ANSI/ASME B18.3
Dimension Size (in)
MinMax
Head Diameter 1.105 1.125
Head Height 0.355 0.375
Hex Socket Size 7/16 (0.437 in)
Hex Socket Flat Head – ANSI/ASME B18.3
Dimension Size (in)
MinMax
Head Diameter 1.355 1.438
Head Height 0.396 Not specified
Hex Socket Size 1/2 (0.5 in)
Slotted Flat Head – ANSI/ASME B18.6.3
Dimension Size (in)
MinMax
Head Diameter 1.215 1.285
Head Height 0.372 Not specified
Slot Width 0.131 0.149
Slot Depth 0.111 0.171
Phillips Flat Head – ANSI/ASME B18.6.3
Dimension Size (in)
MinMax
Head Diameter 1.215 1.285
Head Height 0.372 Not specified
Drive Size 5
Phillips Pan Head – ANSI/ASME B18.6.3
Dimension Size (in)
MinMax
Head Diameter 1.375 1.435
Head Height 0.488 0.521
Drive Size 5
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Frequently Asked Questions

What is the tap drill size for 3/4″-10, 3/4″-16, and 3/4″-20 screws or bolts?

Tap drill selection is based on the material and required thread engagement. For aluminum, brass, or plastic (75% thread), a 21/32″ (0.656″) drill bit is specified for 3/4″-10, an 11/16″ (0.688″) for 3/4″-16, and a 45/64″ (0.703″) for 3/4″-20. For steel, stainless, or iron (50% thread), an 11/16″ (0.688″) drill bit is recommended for 3/4″-10, a 45/64″ (0.703″) for 3/4″-16, and a 23/32″ (0.719″) for 3/4″-20.

What clearance hole size is needed for a 3/4″ screw or bolt?

For a Close Fit, a 49/64″ (0.766″) drill bit is utilized. For a Normal/Free Fit (standard clearance), a 25/32″ (0.781″) drill bit is specified to allow the screw or bolt body to pass through the material without interference.

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.