Glossary
Twenty-six terms that decide whether a part works — written as plain statements rather than as specifications, because a definition is only useful if it changes a decision.
Forming a part from wire by striking it into a die at room temperature. It wastes almost no material and work-hardens the steel as it deforms.
Cold heading through a sequence of dies in one machine, so a part can gain several diameters, a head and a bore without leaving the press.
Forming a thread by displacing material rather than cutting it. The grain follows the thread profile, which raises stripping torque and fatigue life.
A screw with a washer pre-assembled to it, usually held by an undercut and the rolled thread. Removes a loose part from the assembly line.
A screw supplied with one or more captured washers — flat, spring or both — so the washer cannot be omitted during assembly.
A screw or pin with two or more diameters. The shoulder locates a part, carries a radial load or acts as a pivot.
The transition diameter on a stepped part. Its concentricity with the shank decides whether the assembly binds.
A pin whose mass is deliberately offset from the axis, used to convert rotation into vibration in micro motors.
A screw with a drill point that cuts its own hole, removing the need to pre-drill. Case depth at the point controls performance.
A screw that forms or cuts its own thread in plastic, wood or thin sheet. Thread form must match the mating material.
The undercut depth that keeps the washer on the screw — loose enough to rotate freely, tight enough not to fall off in a feeder.
The torque at which a thread fails in the mating material. Rolled threads and correct thread form raise it.
The tendency of a driver bit to slip out of the head under torque. Head geometry and bit wear both drive it.
The clamp force left in a joint after tightening. Washers and thread geometry determine how much is retained under vibration.
How closely two diameters share an axis. On a stepped part it decides fit and wear, not just appearance.
The offset of the thread axis from the part axis. On long screws it decides whether a nut cross-threads at the far end.
Deviation from a straight line over the full length. On a 300 mm screw it decides whether a battery module stacks without force.
A neutral salt fog test measuring hours to red rust. It is the only meaningful way to specify corrosion performance.
A chemical treatment that restores the oxide layer on stainless steel after machining or handling.
An electroplated zinc alloy coating that reaches 720 hours or more of salt spray, used outdoors and in automotive.
Failure caused by hydrogen absorbed during acid cleaning or plating in high-strength steel. Prevented by baking after plating.
A controlled heat treatment after plating that lets hydrogen escape. Mandatory above roughly property class 10.9.
The strength designation of a bolt, such as 8.8 or 12.9. Higher classes need heat treatment and post-plating baking.
The hardened layer on a self-drilling screw point or a wear surface. Too shallow and the point dulls, too deep and the part is brittle.
The die set that forms a headed part. Owning the dies is what makes sampling fast and repeat orders stable.
How much a diameter is reduced between heading stations. Exceeding the limit cracks the head.
Feasibility, process route and an indicative price in 48 hours — including when the answer is that turning is the better route.
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