Previous pages discussed the standard AN airframe bolt AN3 - AN20
. We continue here with the Clevis bolt (AN21 - AN36) usually used in shear applications and some countersunk bolts like the AN509. We also give some attention to the eye bolt and the washer head screw.
The countersunk bolts are used in places where the standard AN bolt would not fit due to its larger head. They are sold in different lengths and thread sizes.
The Clevis bolts are to be used in applications subject to shear stresses only, and are often used as mechanical pins in control applications like throttle cable connection to the carburettor or fuel injection system of an engine. A clevis is a U-shaped fitting similar to a shackle. The clevis is not to be used in tensile load applications.
They have a slotted brazier type head and are special-purpose bolts for use where a large shearing stress occurs (never in tension). Minimum tensile strength is 125,000 PSI. You can buy them drilled or undrilled in the shank, designated with an A for an undrilled bolt.
Clevis pin
A slightly different version is the clevis pin (MS20392 or AN392 - AN406). With the Clevis pin you do not use a bolt but a cotter pin or ring to safety the pin. Whereas with the clevis bolt a castle nut and cotter pin would be used and in certain situations a self locking nut can be applied as well.
Diameter and length of a clevis pins is designated by the number after the dash in 1/32 inch. For example a AN392-9 is 1/8 dia by 9/32 inch length. The AN393 is a 3/16 diameter pin with the number after the dash indicating the length in 1/32 inch, thus a AN393-9 is 9/23 inch and a AN393-11 is 11/32 inch. An AN394- is 1/4 inch diameter.
Material
The Clevis bolt is made of a nickel steel alloy, SAE 2330.
Diameter
For the AN12 - AN23 bolt the second digit denotes the fine thread machine screw size, ie AN21 = 6-40, AN22 = 8-36 and AN23 = 10-32. For the AN24 - AN36 bolts the second digit denotes the diameter in 1/16 inch increments. For example the AN25 has diameter of 5/16 inch.
Length
The number following the dash indicates the length of the bolt in 1/16 inch. AN21-9 indicates a length of 9/16 inch and an AN21-26 is 26/16 inch or 1-5/8 inch.