Fastener Single Shear Test Fixtures (MIL-STD-1312-20 / NASM 1312-20)

Model No. WTF-SS (Stainless Steel & Hardened Steel Inserts)

NASM 1312-20 Conf. 3 Single Shear 2

Fig. 1: Standard Fastener Single Shear Fixture with Extra Blades

These fixtures are used to test, in single shear, fasteners (typically metallic) which are not long enough to be tested in double shear. Double shear being the preferred method, single shear testing should only be used if fasteners are not long enough to be tested in double shear as specified in Figure 1 of MIL-STD-1312-13. As a general rule the length of a fastener must be at least double the nominal diameter in order to use a double shear fixture. Our standard fixture (Figure 1) is designed off of Figure 3a. of the 1312-20 standard. We can make fixtures of the other figures as well.

The fastener to be tested is inserted through the two hardened steel blades, each blade having an accurately toleranced hole of the same diameter as the fastener. The removable blades allow the same fixture to be used to test different sizes of fasteners, requiring only the blades to be customized for each size of fastener. A compressive force is then applied to the top of the fixture to single-shear the fastener.

Single Shear 5

Fig. 2: Disassembled Fastener Single Shear Fixtures

Source of Additional Information:
1) "Fastener Test Methods, Method 20, Single Shear," Military Standard MIL-STD-1312-20, July 1985, also National Aerospace Standard NASM 1312-20, August 1997.