Sharp vee threads shown for clarity; the crests and roots are actually flattened or rounded during the forming operation.
Fastener Definitions
anchor bolt - a steel rod or bar, one end of which is intended to be cast in concrete while the opposite end is threaded and projects from the concrete for anchoring other material to the concrete.
bolt - a headed and externally threaded fastener designed to be assembled with a nut.
cold forming - the process of forming material below the recrystallization temperature by forcing or pressing metal into various dies.
cut thread - produced by removing material from the surface with a form cutting tool.
decarburization - a loss of carbon from the surface layer of the fastener, normally associated with heat treatment.
destructive test - a test to determine the properties of a material or the behavior of an item which results in the destruction of the sample or item.
eye bolt - a threaded lifting eye which has a defined breaking strength and proof load requirement.
full size specimen - tension test specimen consisting of a completed fastener for testing in the ready to use condition without altering the configuration.
plain washer - a fastener accessory that accepts a bolt or screw through its center hole and provides a surface to distribute bearing stress. It also serves to provide a surface for head or nut rotation during tightening.
plating - deposition of an adherent metal onto the surface of the base metal of the fastener. A specific process should be specified; that is, electroplating, hot dip galvanizing, mechanical deposition, etc.
proof load - a specified load that the product must withstand without measurable permanent set.
roll thread - a thread produced by action of a form tool which, when pressed into the surface of a blank, displaces material radially.
structural bolt - a heavy hex head bolt having a controlled thread length intended for use in structural connections and assembly of such structures as buildings and bridges.
total case depth - the distance measured perpendicularly from the surface of the hardened or unhardened case to a point where differences in chemical or physical properties of the case, when compared to the core, are no longer distinguished.
traceability - the ability to verify the manufacturing history, raw material, heat number, location, or application of an item by means of recorded identification.
from ASTM F1789-98 and F606-95b
Terminology of Screw Threads
Sharp vee threads shown for clarity; the crests and roots are actually flattened or rounded during the forming operation.
Hexagonal-Head Bolt
Note the washer face, the fillet under the head, the start of threads, and the chamfer on both ends. Bolt lengths are always measured underneath the head.
The thread length of inch-series bolts is
and for metric bolts is
where the dimensions are in millimeters.
Hexagonal Nuts
End view,
generalWasher-faced
regular nutRegular nut chamfered
on both sidesJam nut with
washer faceJam nut chamfered
on both sides
Typical Cap-Screw Heads
fillister head flat head hexagonal socket head
Types of Heads Used on Machine Screws
Round head Flat head Fillister head Oval head Truss head Binding head Hex head (trimmed) Hex head (upset)
The above images taken from Mechanical Engineering Design, 5th Ed, by Shigley & Mischke, McGraw-Hill, 1989, pp 326-36.
