|
Glossary of Fastener Terminology
P
Passivating: Passivating is the process of
dissolving ferrous particles and surface impurities
from stainless steel by chemical means (normally a
nitric acid dip) and to produce a passive film on
the surface. The purpose is to improve the corrosion
resistance of the surface.
Physical Properties:
Physical properties are the properties defining the
basic characteristics of the material or fastener,
They are inherent in the raw material and remain
basically unchanged in the fastener following its
manufacture and include: density, coefficient of
thermal expansion, electrical conductivity, thermal
conductivity and magnetic properties.
Performance Properties: Functional design
features manufactured into the fastener to satisfy
various requirements of the service application such
as locking ability, prevailing torque, etc.
Pickling: Pickling is the process of removing
surface oxides or impurities by chemical or
electrochemical means.
Piles: Term used in structural engineering for
the joint plates.
Pin: A pin is a straight cylindrical or
tapered fastener, with or without a head, designed
to perform a semipermanent attaching or locating
function.
Pitch: The distance; measured parallel to
fastener axis, between corresponding points on
adjacent thread forms in the same axial plane and on
the same side of the axis.
Pitch Diameter: On a straight thread, the
diameter of the coaxial cylinder, the surface of
which would pass through the thread profiles at such
points as to make the width of the groove equal to
one-half of the basic pitch. On a perfect thread
this occurs at the point where the widths of the
thread and groove are equal.
Pits: Pits are sharp depressions on the
surface of a raw material or fastener.
Plain: Plain as applied to finish of
fasteners is used to indicate that the fastener has
had no supplementary surface treatment, such as
plating, coating, etc., other than being oiled.
Plating: Plating is the application of a
metallic deposit on the surface of the fastener by
electrolysis, impact, or other suitable means.
Plating Build Up: Plating build up is the
term used to describe the disposition of more
plating on edges or corners than on the other
surfaces of the fasteners.
Ply:
A single thickness of steel forming part of a
structural joint.
Point: The point of a fastener is the
configuration of the end of the shank of a headed
fastener or of each end of a headless fastener.
Points of fasteners fall into the general categories
described and illustrated below:
Chamfer Point: A chamfer point is a
truncated cone point, the end of which is
approximately flat and perpendicular to the
fastener axis. These points on threaded
fasteners generally have point included angles
of 45 to 90 degrees and a point diameter equal
to or slightly less than the minor diameter of
the thread. This point is intended to facilitate
entry of fasteners into holes at assemble.
Cone Point: A cone point is a sharp
conical point designed to perform perforating or
aligning functions at assembly.
Gimlet point: A gimlet point is a
threaded cone point usually have a point angle
of 45 to 50 degrees. It is used on thread
forming screws such a Type “A” tapping screws,
wood screws, lag bolts, etc.
Oval Point: An oval point is a radiused
point, sometimes referred to as a ‘Crowned End’
or “Round Point.”
Point Diameter:
The point diameter is the
diameter of the point measured at the extreme
end of the fastener. It may sometimes be
designated as “Chamfer Diameter” or ‘Pilot
Diameter” on respective point types.
Point Length:
the point length is the length of the pointed
portion of the fastener, measured parallel to
the axis of the fastener from the extreme end.
It may sometimes be designated a “Chamfer
Length” or Pilot Length” on respective point
types.
Point Radius:
The point radius is the spherical radius on an
oval or spherical point.
Plain
Point:
The term plain point is applied
to the end of a fastener cut approximately flat
and perpendicular to the fastener axis. These
points on threaded fasteners may be slightly
concave especially when threads are rolled.
Spherical Point.
A spherical point is an oval
point in which the point radius is equal to half
the shank diameter.
Pointing:
Pointing is a secondary machining
operation consisting of cutting points on fastener
blanks which were not pointed during the heading
operation.
Polishing:
Polishing is the process of producing
a smooth surface by rubbing with fine abrasive
wheels, belts, or compounds.
Pooching: Pooching is a term sometimes used to
describe the effect of the area immediately
surrounding a tapped hole being raised up as a
result of the tension from the stud. Tapped holes
are often bored out for the first couple of threads
to eliminate this problem.
Position tolerance: The
axis
of the feature shall fall within or
pass through the zone bounded by a circle about the
true position or reference axis whose diameter is
the position tolerance.
Precision: Precision is the
result of being manufactured to close tolerances.
Preload: The tension created in a fastener when
first tightened. Reduces after a period of time due
to embedding and other factors.
Prevailing Torque: The torque required to run a
nut down a thread on certain types of nuts designed
to resist vibration loosening. The resistance can be
provided by a plastic insert or a noncircular head.
Proof Load: A proof load is a
specified test load which a tastener must withstand
without any indication of failure.
Proof Test: A proof test is
any specified test required for a fastener to
indicate that it is suitable for the purpose
intended.
Property Class: A designation system which
defines the strength of a bolt or nut. For metric
fasteners, property classes are designated by
numbers where increasing numbers generally represent
increasing tensile strengths. The designation symbol
for bolts consists of two parts:
-
The
first numeral of a two digit symbol or the first
two numerals of a three digit symbol
approximates 1/100 of the minimum tensile
strength in MPa.
-
The
last numeral approximates 1/10 of the ratio
expressed as a percentage between minimum yield
stress and minimum tensile stress.Hence a
fastener with a property class of 8.8 has a
minimum tensile strength of 800 MPa and a yield
stress of 0.8x800=640 MPa.
The
designation system for metric nuts is a single or
double digit symbol. The numerals approximate 1/100
of the minimum tensile strength in MPa. For example
a nut of property class 8 has a minimum tensile
strength of 800 MPa. A bolt or screw of a particular
property class should be assembled with the
equivalent or higher property class of nut to ensure
that thread stripping does not occur.
Punching: Punching is the
process of trimming or removing material with dies
in a press.
Prying: The amplification of an external force
acting on a bolt by a lever action which can occur
when that force is an eccentric tensile load.
(Click on the
letters below to browse the glossary terms)
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y
Z |
