• Within a given diameter (i.e. 1/4, 3/8, 1/2, etc.) of any AN/MS/NAS series, all bolts will have the same thread  length, no matter how long the bolt.

• The thread lengths for each series bolt are on the specification prints and in a chart under the "Aerospace Bolt Interchange" heading under Tech Info

• In all MS and NAS series bolts, the dash number is the grip in 1/16" (0.0625") increments, e.g. -18 = 18 x 0.0625" = 1.125" = 18/16".

• Thus, to determine the overall length of a bolt, simply add the thread length for that series and diameter to the grip length you desire, e.g. NAS 1306-24: grip is 1.50" + threads: 0.578" = 2.078" overall length.

• In AN series bolts, you must have a chart or bolt gauge to determine lengths, grips or part numbers. THE DASH NUMBERS DO NOT INDICATE EITHER GRIPS OR OVERALL LENGTHS.

Shear Capacity Calculation

To roughly calculate the ultimate single shear capacity of an aircraft bolt, multiply bolt area at full shank diameter times ultimate shear strength rating, e.g. NAS 1304 bolt, 0.250" diameter:

Area = πr²; 3.1416 x 0.125" x 0.125" = 0.0491 square inches;

Rating per specifications for 1304 series is 95,000 psi;

Single shear = 95,000 psi x 0.049 = 4665 lbs. at full diameter

Tensile Strength Capacity Calculation 

To calculate the ultimate tensile capacity, multiply bolt area at maximum pitch diameter (see chart below) times ultimate shear strength rating, e.g. NAS1304 bolt, 0.250" diameter:

Area = πr²; 3.1416 x 0.1134 X 0.1134 = 0.404 square inches. Rating per specifications for 1304 series is 160,000 psi; 0.404 x 160000 = 6464 lbs ultimate tensile strength.

EXTERNAL THREADS "J" TYPE (CONTROLLED RADIUS ROOT) CLASS 3A

PER MIL-S-8879C (DIMENSIONS IN INCHES)

SIZE-THREADS

PER INCH