McGuire Glossary of Fastener Terminology

O - 40 terms

OAL - Length of an extension spring from end to end

OBLIQUE LOAD - A load that is applied to an anchor, which can be resolved into tension and shear components.

OCTAGON HEAD - A bolt or screw whose head cross section is a regular polygon with 8 sides.

OD - Outside diameter . ID + (2 x wire size)

OFFSET - (1) A condition created in a forging when the dies used in the forging operation do not align properly. (2) The alignment of the upper and lower dies in the hammer or press.

OFFSET - This design feature is a end in the material at the gap. This provides flat and parallel surfaces for ease of installation.

OFFSET FINGERS - A special design of transfer finger where the gripping portion of the finger has been moved away from or closer to the face of the dies. This is done to aid in the transferring of the part between forming stations.

OFFSETS - Offsets are used by a CNC controller to tell a machine where a part is.

OGIVAL - Dies are having radial non-cutoff Ogival point, extensively used for automotive application in the powertrain and assemblies.

OIL QUENCH - A quench from the hardening temperature, in which oil is the cooling medium.

OIL QUENCHING - Hardening of carbon steel in an oil bath. Oils are categorized as conventional, fast, martempering, or hot quenching.

OILED - The term denoting the application of a suitable corrosion retarding oil to a fastener.

ONE PIECE FLOW - The concept of reducing production batch sizes to a minimal amount, preferably a single unit. This can have dramatic effects or raw materials, WIP, finished goods inventories, production lead times, quality and costs.

ONE-WAY SLOT DRIVE - One-way screws are special tamper-resistant screws that can be turned only in one direction. They can be installed with a standard flat-blade screwdriver, but cannot be easily removed using standard tools. One-way screws are practical only when the need for removal is unlikely.

OPEN DIE FORGING - Forging produced by working between flat or simple contoured dies with unrestricted metal flow using repetitive strokes and continuous manipulation of the workpiece; sometimes called hand forging.

OPEN DIES - Dies with flat surfaces that are used for preforming stock or producing hand forgings.

OPEN END - The end of an open coiled helical spring in which the helix angle of the end coil has not been progressively reduced.

OPEN ENDS (SPRING TERM) - Ends of compression springs with a constant pitch for each coil.

OPEN EXTRUSION - This refers to a forward extrusion where a portion of the incoming blank is not contained within the tooling before the extrusion takes place.

OPEN UPSET - The outside surface of the upset material is not contained by any tooling cavities at the end of the forming stroke.

OPSIT DRIVE - The OPSIT screw drive has left-handed threads and is a Tri-Wing design drive fastener.

ORANGE PEEL - A finish resembling the dimpled appearance of an orange peel.

OUTEND - In screw machine work the end which is made out or opposite the cutoff end.

OUTER DIAMETER - The exterior surface of a spherical or cylindrical object.

OUTSIDE DIAMETER O.D. (SPRING TERM) - The diameter of the cylindrical envelope formed by the outside surface of the spring coils.

OVAL DRIVE - The Oval drive tamper-resistant screw drive is a proprietary screw head from Jura Elektroapparate with an eccentric oval to dissuade users from servicing their own machine.

OVAL HEAD 82 - A countersunk head with a rounded top surface and a cone-shaped bearing surface of approximately 82 Degrees. Preferred over a flat head in conical applications or when a more decorative finished look is desired. The countersunk surface nests into mating countersunk application sites.

OVAL HEAD METRIC 90 - A countersunk head with a rounded top surface and a cone-shaped bearing surface of approximately 82 degrees. Preferred over a flat head in conical applications, or when a more decorative finished look is desired. The countersunk surface nests into mating countersunk application sites.

OVAL HEAD UNDERCUT 82 - Similar to an 82 degree oval head except that the head is undercut to 70% of it normal height. Standard for short lengths because it allows greater thread length.

OVAL POINT - A radiused point that is mostly found on socket set screws for specific applications.

OVER MOLDING - This process froms a shape on top of another object. Typically plastic is over molded onto metal or another plastic. This process is similar to injection molding except that the cavity includes a fixture part that the injected material forms around.

OVERETCH - In the normal processing of aluminum forgings, a caustic etch operation is employed for the dual purpose of cleaning parts and emphasizing defects to facilitate visual inspection. Immersion of parts for too long or use of too concentrated a solution will produce a rough, slightly pitted surface.

OVERFILL - A portion of the formed part which has too much metal to give it the full shape of the tooling impression or cavity. Usually creates a fin or burr.

OVERHEATED METAL - Metal with an undesirable coarse grain structure due to exposure to an excessively high temperature. Unlike a (burnt) structure, the metal is not permanently damaged but can be corrected by mechanical working or suitable heat treatment.

OVERLAY - A transparent large scale (generally 31.25 X) drawing of min. and max. material condition used for rapid inspection of parts.

OVERLOAD - A condition where a hydraulic, pneumatic, or mechanical press exerts a force beyond its capacity. Overload protection systems are typically put in place to prevent damage to the press.

OVERTAPPING - Tapping of a thread following a plating operation so that the thread tolerances comply within specification allowing the internal and external threads to assemble. It is normal practice to overtap the internal rather than the external thread.

OXIDATION - A reaction in which electrons are removed from a reactant. Sometimes, more specifically, the combination of a reactant with oxygen.

OXIDATION - A reaction in which electrons are removed from a reactant. Sometimes, more specifically the combination of a reactant with oxygen.

OXIDIZING AGENT - A compound that causes oxidation, thereby itself becoming reduced. pH: The negative logarithm of the hydrogen ion activity (less precisely, concentration) as determined by indicators or electrometric means; used as a measure of the acidity or alkalinity of a solution.