Cotter Pins Dimensions Calculator was developed according to ASME B18.8.1 standard to show dimensions of cotter pins (Inch).

The cotter pins are intended for use with clevis pins and in pinned bolt and nut assemblies or other type of free fitting pinned assemblies in general applications.

Some important notes from the ASME standard:

- The preferred point type shall be the extended prong - square cut or hammer lock designs.

- The misalignment of prongs over entire length of shank shall not stop pin from being inserted into the gauging hole.

- Materials: Low carbon steel. Pins may also be made from ASTM A493, Types 302 (UNS S30200) and 304 (UNS S30400), corrosion resistant steel; ASTM B134, Alloy 260 (UNS C26000), cartridge brass; Monel Alloy (UNS N04400)

- Each prong of the cotter pin shall be capable of withstanding being bent back upon itself once, with no visible indication of fracture occurring at the point of bend.

- Cotter pins are manufactured from approximately half-round wire

- Designation: Name, Nominal Size, Pin Length, Point Type, Material and Finish. Ex: Pin, Cotter, 1/8 x 1, Extended Prong Type, Steel, Zinc Plated


Point Type 
Nominal Pin Size
Pin Length *

Note * : Preferred lengths advised in ASME B18.8.1 standard.


Cotter Pins Dimensions
Parameter Symbol Value Unit
Nominal Size (Basic Pin Dia.) - --- inch
Nominal Size (Basic Pin Dia) - ---
Max. Total Shank Diameter Amax ---
Min. Total Shank Diameter Amin ---
Maximum Wire Width Bmax ---
Minimum Wire Width Bmin ---
Minimum Head Diameter Cmin ---
Extended Prong Length Dmin ---
Gage Hole Diameter
(+/- 0.001)
- ---
Maximum Pin Length Lmax ---
Nominal Pin Length Lnom ---
Minimum Pin Length Lmin ---

Note: Total shank diameter (A) is 2 times wire thickness which is measured at the end of the cotter pin.


Clevis Pin: A type of cylindrical pin with a head at one end and with a hole passes through the diameter at the other end. A clevis pin is generally locked in place with a cotter pin. Clevis pins provide rotation between connected components about pin axis.

  • ASME B18.8.1-1994, Clevis Pins and Cotter Pins (Inch Series)
  • Oberg.E , Jones.D.J., Holbrook L.H, Ryffel H.H., (2012) . Machinery's Handbook . 29th edition.  Industrial Press Inc. , pp 1746