Tallow: animal fat prepared from beef and mutton, sometimes a combination of
solid and fluid fats; acidless tallow is used in the formulation of compounded
cylinder oils to increase wettability properties in the presence of steam. Ordinary
tallow contains 25% fatty acids; acidless tallow contains less than 0.5%.
Total acid number: (TAN): see neutralization number, strong acid/strong base
Tapered pad/land bearing: a fixed pad (land) bearing in which the surfaces of
the pads are tapered to promote the establishment of a hydrodynamic film.
Tapping and plugging: refers to the use of a non-tapered tap, known as a
bottoming or plug tap, after starting threads with two previous tapered taps.
TBN: see neutralization number, strong acid/strong base numbers.
Tricresyl phosphate/TCP: a colorless liquid used as a lubricant additive and
Teflon: polymer of tetrafluoroethene, also known as PRFE; material
trademarked by DuPont.
Temper oil/martempering oil: heavy mineral oil kept at relatively high
temperatures for long periods of time, suitable for tempering operations. Hot
metal is placed in a bath of oil, at a temperature of 400-600°F, after which the
metal and oil are permitted to cool slowly; in the alternative, the hot bath may be
used to heat the metal slowly and uniformly without oxidizing the surface.
Texture (grease): the property of a grease that is observed when a small portion
is compressed, then slowly drawn apart, described in the following terms: brittle,
tends to rupture or crumble when compressed; buttery, separates in short peaks
with no visible fibers; long fibers, tends to stretch or string out into a single
bundle of fibers; resilient, capable of withstanding moderate compression
without permanent deformation or rupture; short fiber, shows short break-off
with evidence of fibers; stringy, tends to stretch or string out into long threads
with no visible evidence of fibrous structure (see bulk appearance).
Thermal Gravimetric Analysis/TGA: a measure of weight loss under specific
conditions; normally, temperature is maintained (isothermal) or increased in an
atmosphere of nitrogen or oxygen; used to study oil volatility and oil residues,
for example, contaminated roll oils.
Thermal conductivity – a measure of a material’s ability to conduct heat
Thermal cracking: a process utilizing heat to break high molecular weight
substances into smaller units; facilitated in a controlled manner during refining
by the presence of a catalyst.
Thief (sample) Bomb: device for obtaining samples of liquid from different
depths in a tank.
Thin film/mixed film lubrication: a condition of lubrication in which the
lubricant film is so thin that the friction between the surfaces is determined by
the properties of the surfaces as well as the viscosity of the lubricant (see
boundary lubrication); also known as mixed film lubrication.
Thixotropy: the property of a material like lubricating grease that is manifested
by a softening in consistency as the result of shearing, followed by a hardening in
consistency that begins immediately after the shearing stops. With thixotropic
cleansers, shearing may occur with shaking, mixing, vibrating, pumping or
Thread cutting oil: Petroleum based product formulated to cool and lubricate
the threading tools that produce external threads on metal rods or pipes. Single-
point tools can be used, but the majority of threading is performed by feeding
special threading dies into the workpiece until the desired length of thread is
Thrust bearing: an axial-load bearing.
Thrust collar: see collar thrust bearing.
Timken OK load: measure of the EP properties of a lubricant. The Timken
testing machine uses a lever arm that can be loaded to bring a stationary block to
bear against the rotating outer race of a bearing until scoring occurs. The
maximum load prior to scoring is called the OK load.
Tolerance: term describing deviation from the prescribed dimensional
specifications for bore, O.D. and ring widths of standard bearings; the slighter
the deviation, the smaller the tolerance and the closer the bearing comes to
precision. The Annular Bearing Engineering Committee has standardized the
tolerances for ball bearings, and the Roller Bearing Engineering Committee has
developed similar tolerances for roller bearings; higher numbers mean greater
Tooth depth (gears): sum of the addendum, dedendum and a small clearance
Total acid/total base numbers: total acid number (TAN) and acid number are
synonymous, indicating the strong acid number values. Total base number
(TBN) reflects all basic constituents, including the strong base component (see
strong acid/base numbers).
TQIT: bearing manufacturers’ nomenclature describing tapered roll-neck,
interference-fit bearings used in high-speed, heavy-duty rolling mills where close
gauge and shape tolerances are required.
TQO: nomenclature used by tapered roller bearing manufacturers to denote the
straight-neck, loose-fit roller bearings used on heavy-duty, low-to-medium speed
Traction fluids: fluids displaying high traction coefficients; under high stresses
they develop a glass-like structure, simultaneously transmitting shear forces and
protecting the contacting surfaces from wear. Cycloaliphatics are superior
Tramp oil: describes undesired oil scum in a system, e.g., lubricants or hydraulic
fluids that mix with rolling oil systems in cold mill areas.
Transducer: an electrical device that converts a signal from one form of energy
Transformer oil: oil suitable for use in a transformer, to dissipate heat, keep the
insulation on the wire pliable and retard the oxidizing effect of the air. Since it
circulates between coils of wires that carry high-voltage currents, it must resist
the flow of current through it from one coil to another; otherwise, the
transformer short-circuits. Such resistance is termed dielectric strength; oil that
is extremely dry, clean and acid-free has high dielectric strength.
Transverse plane (gears): in helical gears, a cross-section (perpendicular) to the
line of action.
Tribology: the science and technology of interacting surfaces in relative motion
and associated subjects and practices. This term, first used in 1966, effectively
coordinates many technical disciplines such as chemistry, metallurgy, machine
design, lubrication engineering, etc., for solving friction and wear problems.
Trunnion: either of two opposite pivots or cylindrical projections from the sides
of an assembly, supported by bearings, that offer a means of swiveling or turning
an assembly or part of an assembly. Trunnion bearings are used with basic
Tung oil/chinawood oil: a drying oil from the seeds of tung trees that dries to a
soft, opaque white film.
Turbulent flow: characterizes flow in eddies and currents through a pipe, in
contrast to streamline, or laminar, flow; turbulent flow causes fluid friction loss.
Flow quality depends on a combination of factors; pipe diameter, fluid density,
viscosity and velocity.