McGuire Glossary of Fastener Terminology

S - 29 terms

SDO - Standard Developing Organization

SDO/CONTENT PROVIDER - Stands for Standard Developing Organization that provides the contents of the standard

SEATING TORQUE (LOADING OR TIGHTENING TORQUE) - A value of torque typically measured in "inch-pounds" applied to a fastener to induce a compressive load under the head bearing surface that results in creating an axial load (pre-load).

SECOND GRIP - For a given type and thread size, the part with the second lowest value of grip range is commonly referred to as a second grip part. The next grip range is a third grip part and so on. For some thread sizes of thick wall parts, the catalog lists six grip ranges, in which case the highest grip range part would be referred to as a sixth grip part.

SHANK - The entire outer portion of a blind threaded insert exluding the head. the counterbore and the threads are both contained within the shank. Shank diameters are typically just under the minimum mounting hole diameter with a modest minus tolerance applied.

SHANK LENGTH - The total axial length of shank plus undercut plus displacer (definition #1) After a self-clinching fastener has been properly installed in the sheet, the distance from the top of the sheet to the end of the shank is also the shank length (definition #2)

SHIM STACKS - Ideal for simple and complex applicadtions as they offer exact dimensions for precise spacing

SHORT-RUN STAMPING - Ideal for small projects and prototypes, short-run metal stamping does not require much upfront tooling to produce a component. The custom nature of short-run stamping operation can create a higher price per piece, but the lack of upfront tooling troughtout the run can make the method cost-efficient for some projects.

SHORTENING - The amount of decrease in overall length that occurs when a blind threaded insert is installed. It is typically slightly less than the free counterbore length minus two times the wall thickness. Inserts shorten more when installed in min grip than when installed near max grip, as a result, the installed height on the blind side of the panel is essentially constant, regardless of grip

SHOULDER - Shoulder washers, also known as "step" or "flange" washers, have an apperance of a low-crowned top hat and an integral cyclindrical sleeve. The sleeve is designed to mate with a cutout and segregates the fastener from the material it is secured to.

SIDE LOAD - The load applied to the fastenr parallel to the clinched panel at a given distance from tdhe panel dthat will cause the clinch feature to fail or yield the panel or fastener. Thinner panel may yield, thicker panel will cause the clinch feature to fail either by push-out on the bending compression side or pull-thru on the bending tension side. Typically, failure occurs when the bending moment resulting from the side load and distance exceeds the bending strength of the installed fastener. Side loads at other distances can be estimated by computing the bending moment from the published load and distance and then dividing by the distance of interest.

SLOTTED SHANK - The generic term for a Plusnut or Plus-Tite insert. Slotting the shank allows larger grip range and also produces a larger bulb diameter than could be achieved with a slotted shank. Slotted shank parts typically have very thick walls and therefore high upset loads. They are sometimes pre-bulbed to reduce the upset load.

SOLDER PAD - Tinned aera on PCB over which Solder paste will be stenciled.

SOLDER PASTE - Solder and Flux slurry

SPIN-OUT - The torsional holding power of an insert relative to the panel in absence of any clamp load. It is typically measured by holding the panel, inserting a screw from the thread end of the part until it bottoms against the part and applying torque until failure. For inserts with round shanks the typical failure mode is the insert spinning in the panel. For keyed inserts or inserts with hex shanks the values will typically be higher and the mode of failure may switch to torsional failure of the insert or thread stripping due to the induced load.

SPIN-PULL - A type of tool that applies the upset load by first turning a mandrel into the threads of the insert with a low torque and then apply a pulling force to the mandrel. After the part has been upset by the pulling action, the mandrel is turned in the opposite direction to remove it. For this reason, a more proper term for this type of tool that is sometimes used is spin-pull-spin. Compared to spin-spin tools, these tools are more complex, heavier, more expensive and more difficult to setup. However, a smooth nosepiece that will not mar the insert head can be used.

SPIN-SPIN - A type of tool that applies the upset load by turning a threaded mandrel into the threads of the insert. The mandrel is driven by an air motor through reduction gearing. A thrust bearing is used to reduce frictional torque resulting from the applied load. Spin-spin tools are light weight and inexpensive and come with varying amounts of gearing. As thread size increases additional gearing is used to increase torque output at the expense of speed. The stall torque is adjusted by air pressure. Operation is simple, spin in to stall and then reverse the trigger and spin out. Hence the spin-spin terminology. To prevent the insert from rotating, a serrated nosepiece must be used and therefore significant marring of the insert head occurs.

SPINWALL TECHNOLOGY™ - A trademark used by AVK to describe how the technology of thin wall parts differs from that of thick wall parts. The major difference they claim is the radial expansion of the counterbore to completely fill the mounting hole before the bulb is formed.

SPOKES - Solid portion of the stencil design that holds the center of the hole to the rest of the stencil pattern.

SPRING-LOADED - A device having a separate movable component that is biased on one direction by a spring.

STAMPING - This process takes a length of sheet metal and forms a part by cutting and folding the metal. This typically is a very high-speed process that yields many pieces in a very shot period of time

STANDARD TORQUE - 2/3 of initial installation value i.e. MIL spec., plus requirement of removals and clamp load. Example: If the maximum initial installation torque is 100 in. lbs, it would be two-thirds at 66 in. lbs with a potential variance ranging between 60-75 in.lbs.

STANDARDS CONNECT - A subscription based access to standards offered to larger groups needing a multiple user license

STANDOFF - A tubular device, usually threaded, for spacing or stacking components.

STENCIL - Screening sheet used to apply solder paste to exposed areas of a PCB.

STEP - That portion of a headed stud blank to which the root and roll out will be applied. Sometimes referred to as the thread rolling step which canbe slightly misleading as threads do not get rolled on to the step.

STROKE - The amount of decrease in overall length that occurs when a blind threaded insert is installed. Therefore, it is numerically equal to the shortening. However, the term stroke is typically applied to spin-pull tools wheras the shortening term is applied to the insert. Most spin-pull tools have an internal stop, which limits the stroke. To setup these tools, the stroke must be properly adjusted so that the insert will be installed properly.

SURFACE MOUNT - Process of applying product to PCB by first stenciling solder paste then placing product on paste and finally heating entire assembly to melt the solder Also known as "reflow soldering."

SWAGING - An operation whereby a reduced diameter of afastener is deformed to secure it to a panel. Also see self-expanding/crush clinch. Note: the atonym of a swaging self-clinching where the panel material is caused to deform.