SUMMER 2026

26 THE DISTRIBUTOR’S

26 THE DISTRIBUTOR’S LINK Larry Borowski President GREENSLADE & COMPANY INC. 2234 Wenneca Avenue, Fort Worth, TX 76102 TEL 817-870-8888 FAX 817-870-9199 EMAIL sales1@greensladeandcompany.com WEB www.greensladeandcompany.com RECESS PENETRATION GAGING: WHY IT MATTERS, HOW IT WORKS, AND WHAT NOT TO USE A fastener recess can look perfectly formed and still fail in assembly. The threads are perfect, the plating is flawless, and the length is exact, but if the recess does not have the correct penetration depth, the driver will not engage, and the fastener will not do its job. The Recess Is Part Of The Drive System When evaluating fastener quality, most attention goes to thread form, tensile strength, and dimensional accuracy. The recess or drive feature that makes installation possible tends to be the last thing inspected and the first thing to cause a problem on the assembly floor or in the field. A fastener drive system is more than the recess geometry alone. It includes the recess in the fastener, the driver bit or key, and the assembly tool. When any element of that system is out of conformance, the consequences range from frustrating to serious. This could mean stripped recesses, fasteners installed at the wrong torque, assembly line stoppages, and in safety-critical applications, joint failures in the field. Among the recess characteristics that cause these problems, penetration depth is one of the most consequential and most consistently overlooked. Proper measurement of penetration depth is not optional. It is specified in the ASME and ISO standards that govern fastener manufacture and inspection. TECHNICAL ARTICLE What Is Recess Penetration Gaging? A recess penetration gage is a precision inspection tool designed to measure the effective depth of a fastener recess. The depth to which a driver of minimum material condition will seat and engage when installing the fastener. It is not simply a depth gage measuring the bottom of a cavity. It measures the functional penetration depth or how far the correctly shaped driver form can enter the recess to achieve the engagement geometry the standard requires. The fundamental design of a penetration gage consists of a body that holds a spring-loaded precisionground penetration element, (also called a penetration point or GO element), and an indicator. The element is shaped to match the geometry of the recess being measured. When the element is placed into the recess and light downward pressure is applied, the indicator reads the depth to which the element enters the recess before contacting the walls. CONTINUED ON PAGE 100