McGuire Glossary of Fastener Terminology

G - 57 terms

G-CODE - G-Code is a term applied to the coding language used to program and instruct a CNC machine.

GAGE - Arbitrary standard for thickness or diameter of sheet metal or wire stock. A measuring tool

GAGE LENGTH - In mechanical testing, the original length of that portion of the test specimen over which strain, change of length, change of area and other characteristics are measured.

GAGE PROTRUSION - A dimension for the control of flush head configuration. Gage protrusion is stated as the distance from the top of the head to a gage block with a hole of specified diameter (gage diameter) when the fastener is placed in the block.

GALLING - A 'cold-welding' process by which male and female threads become fused together under high amounts of pressure. Galling most often occurs with stainless steel fasteners when excessive heat is generated by thread friction causing localized welding of small high spots on the mating thread surface. Continued rotation tears chuck of material from one of the thread surfaces generating a rough, pocked surface condition. When rotation stops some of these welds remain intact, making the threads difficult to disassemble. Most prevalent with fasteners made of stainless steel, aluminum, or titanium because of the oxide surface film that these materials produce.

GALLING - Welding that occurs between the workpiece and tooling surface due to inadequate coating or lubrication.

GALLING - Often referred to as "Cold Welding", galling most often occurs with stainless steel fasteners when excessive heat generated by thread friction causes localized welding of small high spots on the mating thread surfaces. Continued rotation tears chucks of material from one of the thread surfaces generating a rough, pocked surface condition. When rotation stops some of these welds remain in tact, making threads difficult to disassemble.

GALVANIC CORROSION - Accelerated corrosion occurring when two different metals are in contact with moisture. All metals have a specific electric potential so that low level electric current flows from one metal to another. A metal with a high position in the galvanic series will corrode sacrificially rather than one I with a lower position. Stainless steel will corrode before gold, etc. The further the metals are apart on the chart the more current will flow and the more corrosion will occur. Various plating's and coating can be applied to fasteners to prevent this problem. No serious galvanic action will occur by combing the same metals, only dissimilar ones.

GALVANIZE - To treat with hot bath of lead or zinc to prevent rusting.

GANNT CHARTS - A form of a bar chart used to display project planning activities

GAS NITRIDING - A case hardening process where nitrogen is added to the surface of ferrous alloy at a relatively low temperature. Need for quenching is eliminated.

GAS NITRIDING - A case hardening process where nitrogen is added to surface of ferrous alloy at relatively low temperature. Need for quenching is eliminated.

GASSING - Visible evolution of gases from electrodes during electrolysis. Glass bead blasting: A process whereby small spherical glass beads are propelled against a metallic surface for the purpose of cleaning that surface. It is carried out in either the wet or dry state.

GATE (SPRUE) - A portion of the die that has been removed by machining and permits the bar or tongs to be closer t the impression without being smashed.

GATHERING STOCK - An operation by which a portion of the forming stock is increased above its original diameter.

GAUGE - (1) Instrument for measuring, testing, or registering. (2) Numeric scale for metal thickness.

GEL TIME - The elapsed time at which an adhesive begins to increase in viscosity and becomes resistant to flow.

GEMBA - The shop floor or work site.

GEOMET - Is a coating and Geomet 500 was specifically developed for fasteners. It is aesthetically pleasing aqueous based finish.

GIBS - Guides or shoes that ensure the proper parallelism, squareness, and sliding fit between press components such as the ram and the frame. They are usually adjustable to compensate for wear and to establish operating clearance.

GIMLET POINT - A threaded cone point usually having a point angle of 45 to 50 degrees. It is used on thread forming screws, such as Type A tapping screws, wood screws, lag screws, etc.

GO GAUGE - An inspection tool used to check a threaded part against allowed tolerances. There are ring gauges (for external threads) and plug gauges (for internal threads). A GO gauge is designed to thread onto or into the part being inspected.

GO/NO-GO GAUGE - Measuring device with two registration elements which determine if a feature to be measured is between two established limits.

GOUGE - Surface imperfection, deeper than a scratch, often with raised edges.

GRADE - A rating in a scale classifying fastener according to strength.

GRADE INDENTIFICATION SYMBOLS - Permanent markings denoting the specification used to manufacture a fastener. This would include the appropriate material, mechanical properties and other criteria used to produce the fastener

GRADUATED SHOULDER - Bigger head increases hold power on ETX wood screws.

GRAIN - An individual crystal in a polycrystalline metal or alloy.

GRAIN DIRECTION - (1) Crystalline orientation of material in the direction of mill rolling. (2) Orientation of a surface finish generated by abrasive method.

GRAIN FLOW - Fiber-like lines appearing on polished and etched sections of forgings that are caused by orientation of the constituents of the metal in the direction of working during forging. Grain flow produced by proper die design can improves the mechanical properties of forgings.

GRAIN GROWTH - An increase in the size of the grains of a metal with a proportional reduction of the number of grains.

GRAIN SEPARATION - In forging aluminum, rapid metal flow sometimes causes a separation or rupture of grain. Metal flow is affected by lubricant, die and metal temperature, part shape, alloy, and hammer operator technique; consequently, any one or combination of these factors can cause grain separation. The irregular crevices are seldom more than a few thousandths of an inch deep and can be removed by grinding or polishing.

GRAIN SIZE - An expression that rates the number of grains per unit area of cross section as determined by metallographic examination.

GRAIN SIZE - An accurate assessment of grain size in a given metallic sample is used to determine the effectiveness of a specific manufacturing process (e.g. heat treating or tempering). Technicians prepare the sampling by mounting a cross section, polishing it, and etching it. Etching reveals the grain. Once the sample is prepared, there are several procedures a technician can perform to determine the precise grain size of the specimen.

GRAINS - The individual crystals of the material, which observed by eye or under the microscope is the Grain Structure.

GRAPHITIZING - Annealing in such a way that some or all of the carbon is precipitated as graphite.

GRAVITY HAMMER - A class of forging hammer wherein energy for forging is obtained by the mass and velocity of a freely falling ram and the attached upper die. Examples are board hammers and air-lift hammers.

GREEN CHROMATE - Is a finish that is generally used on steel, aluminum, and zinc. It decreases corrosion rate and can be used as a decorative finish.

GRIND RELIEF - A small undercut added to the inside or outside diameters of tooling components to make the finish grinding of the component easier.

GRINDING - Process of removing material by abrasion.

GRINDING - The removal of material by means of rotating rigid wheels containing abrasive.

GRINDING - Removal of round-shaped material at the ends of the spring for the purpose of making the spring stand flat and square on a flat surface. The ends are made flat by grinding to provide a flat surface.

GRINDING (Spring Term) - The process of removing material from the surface by the cutting action of a bonded abrasive wheel.

GRIP - In general, the grip of a fastener is the thickness of material or parts which the fastener is designed to secure when assembled.

GRIP - The actual thickness of the panel or stack up of panel into which the insert is installed. All performance testing of blind threaded inserts should report the grip used, as it can have a significant effect on performance

GRIP ACCOMMODATION - The allowable variation of material thickness in which a specific fastener can function

GRIP LENGTH - The distance from under the head of a fastener to the beginning of the mating internal threads of a tapped hole or nut.

GRIP RANGE - The difference between the minimum and maximum grip at which a fastener will operate.

GRIP RANGE - Range of panel thickness values into which a given part can be properly installed. It is common practice in the blind threaded insert industry to embed the maximum grip into the end of the part.

GRIPPER DIES - The lateral or clamping dies used in a mechanical upsetter or forging machine.

GRIT BLASTING - Abrasive blasting with small angular pieces of steel or cast iron.

GROMMET - A large eyelet type fastener designed for securing by curling the tubular end over a formed washer to provide strength in holes through resilient materials.

GROOVE - A channel in the surface of a part which can be used to retain material, lock mating parts in place, or as a part identifier.

GROUND THREAD - A thread finished on the flanks by a grinding operation.

GUIDE - The parts of a drop hammer or press that guide the up-and-down motion of the ram in a true vertical direction.

GUIDE TUBE - A tooling component in the wire line of a machine between the wire payoff reel and the feed rolls or grips. It controls the wire as it moves through the sound enclosure and/or between the straightener rolls and the feed rolls or grips.

GUTTER - A shallow impression machined around the periphery of a forging die impression outside the flash land that acts as a reservoir for excess metal.