Fastener testing accessories allow for the performance of proof tests, axial and wedge tensile tests, and cone stripping tests on most standard bolts, screws, studs, and nuts. They are compatible with most universal and tensile testing machines. Available accessories consist of: fastener holders, washers, short bolt adapters, nut proof loading assemblies, and holder reducing assemblies.
Fastener holders are the main component for performing fastener testing. They are used in conjunction with any of the other fastener accessories. Five different fastener holder sets are available, with capacities ranging from 150 to 1500 kN (33,750 to 337,500 lbs).
Fastener holders are threaded on the adapting end to mount easily to either spherically seated tension rods or other adapters. When adapters are ordered (catalogue number W-5118), either separate adapters will be supplied as needed or the fastener holders will be threaded to meet the mounting dimensions specified. Fastener holders can also be ordered with standard Instron attachment styles that are either a pin & clevis or a metric, male threaded interface.
Each fastener holder has a key slot that allows the operator to quickly and correctly load the specimen. A recessed circular area in the bottom of each fastener holder ensures that the washer will fit snugly (sheet metal alignment device is used on Series E holders). This reduces loading time and occurrences of slippage, because a secure, centered seating is ensured for each test.
Principle of Operation
The most common integral components used with fastener holders are washers. Washers provide the interface between the fastener being tested and the holder. For a typical test, the operator would fit an unthreaded washer under the head of a screw or bolt and a threaded washer onto the threaded section of the fastener (when testing studs, two threaded washers will be used, one on each threaded portion). After fitting the specimen with both washers, the operator would place the fastener into the holder, apply a pre-load to ensure correct seating and adjust the alignment, and begin the test.
Nut proof loading assemblies are designed for testing nuts. They are available for all fastener holder series and consist of a hardened proof loading mandrel and a proof loading plain flat washer. When used to perform cone stripping tests, a conically shaped plain washer must be used.
Short bolt adapters can be used to enable testing of bolts that are too short for standard fixtures. There are two varieties: tophat adapters for smaller diameter bolts and dumbbell adapters for larger diameter bolts.
The last fastener testing accessory, holder reducing assemblies, are not used to test fasteners. Rather, they allow a smaller bolt holder or other fixture to be mounted to a bolt holder already in the frame. This assembly minimizes time-consuming fixture changes and additional accessory costs.