Fit: Assembly of a outer container
part (bore) and an inner contained part (shaft). The male (shaft)
and female (bore) parts have the same nominal size but different
tolerances offering either positive play, clamping or uncertain
play. Boring: Operation which consists of carefully machining the
inner surface of a cylinder or any other hollow part. The result
of this operation is known as a bore. Shaft: Mechanical member transmitting
power in the form of torque and rotary movement. The cylindrical
shape of this member is what gives it its name.
Pin: Straight mechanical part around which one or more other parts
rotate. Its sole purpose is to guide a rotation or translation movement.
The choice of diameter is very important for pins. For correct guiding,
the length must be at least twice the value of the diameter.
Chain pins are generally solid, but they can be hollow and used
for attaching accessories or spacers connecting two chains operating
Burr: Refers to unwanted excess material, often very thin, as if
the material had been smudged. It is anti-aesthetic and can be sharp.
Bloom: Steel bar with a square or rectangular cross-section larger
than a square of 120 mm (160 mm for certain steel industries), with
variable length intended for being inserted in rolling trains referred
to as finishing mills.
Bolt: Assembly member made up of a screw with a uniform thread and
flat end (or threaded rod) and a nut (and optionally a washer).
Carburisation: Thermochemical treatment which consists of making
carbon penetrate the surface of a steel in which the carbon percentage
is too low to be hardened, in order to transform the surface into
a highly-carburised steel that can be hardened.
Breaking load: Weight of the load that causes the chain to break
(permanent deformation or destruction)
Key: Metal fastening inserted by force in a notch made in a part
in order to rest against another part or between two parts in order
to secure them to one another and prevent rotation.
Safety factor: In order to determine the breaking load of a chain,
a safety factor of the force F needs to be applied.
Breaking load = F x safety factor
This factor is dependent on the operating conditions. It can range
from 5 to 12, but is generally between 7 and 10. It is advisable,
however, to check the joint pressure before ultimately choosing
the chain, since this can be a determining factor.
Drawing coefficient (DC): Variable parameter according to the condition
of the raceway, the lubrication, the diameter of the chain roller,
-0.10 for a chain with standard rollers, good lubrication and clean
-0.15 for a chain with standard rollers, uncertain lubrication and
-0.20 for a chain with small rollers, uncertain lubrication and
-0.33 for direct friction of the link plates on the steel raceway
-0.02 to 0.05 for ball rollers (the larger the diameter of the roller,
the lower the coefficient)
Conveyor: Continuous handling apparatus in a closed circuit, providing
overhead or ground-level transport of loads or materials.
Screen rake: handling apparatus for removing the refuse that builds
up on the screens.
Gear teeth: Set of teeth of a sprocket wheel; generally cut; can
also be flame-cut and ground for special profiles or for very large
Pitch diameter: distance between the centre of the wheel and the
approximate middle of the teeth.
PD = pitch/sin(180°/no. teeth)
Ductility: Refers to the capacity of a material to deform plastically
without breaking. Breaking occurs when a defect (crack or cavity)
becomes critical and spreads.
Bushing: Cylindrical metal nozzle used to assemble two parts, by
protecting the pin.
Hardness: For metals, defines the resistance of the surface of the
sample to penetration by a harder body, for example the ball or
the tip of a hardness tester.
Sluice: Structure built between two bodies of water on different
levels, which allows boats to pass from one to the other and vice-versa
by means of opening and closing mobile elements, doors and valves.
Elevator: Appliance or engine used to transport loads or materials
vertically or on very steep slopes.
Enamelling: Depositing a vitreous, transparent or coloured layer
on a metal or another substrate. The part to be enamelled is covered
with pigments, in suspension in a volatile oil, and then exposed
to a temperature of around 800 °C; the oil evaporates and the
molten pigments are bonded to the surface. Enamelled parts have
great durability, excellent resistance to scratching and chemical
agents, and are easy to clean.
Spacer: Tube-shaped part intended for maintaining a constant separation
between two ball bearings.
Coating: Metered mix of aggregates and filler coated with bitumen
or tar, used for the top layers of pavements and for watertight
covering of canals or dams.
Shoulder: Sudden change in diameter, generally in order to provide
a bearing surface for another part.
Oven: Enclosure with a very high temperature and humid heat.
Excavator: Earthmoving plant provided with a bucket chain mounted
on a roller track or a bucket wheel.
Threading: Consists of one or more helical grooves on a cylindrical
Roller: Chain roller with a diameter greater than the height of
the link plates. It allows the chain to roll over a flat surface.
Rollers can be straight or shouldered in order to provide lateral
guiding. The straight or shouldered rollers are made from treated
Bucket: Type of trough with variable capacity and shape, used in
a certain number of handling apparatuses (dredger, elevator, bucket
loader, etc.) for digging the ground.
Cotter pin: Small metal part which is inserted in the end of certain
elements so that the assembly forms a removable rigid unit. It can
be used to immobilise or position a part in relation to one another,
acting as a pin or a safety part (shearing in the event of an overload)
Greaser: Device which, in a machine, automatically supplies grease
or lubricant to moving members.
Shot-blasting machine: Machine which blasts shot in the form of
micro-balls in order to strip a surface of the material that covers
Seizing: Mechanical accident between two metal surfaces rubbing
against one another, when metal particles come loose from one surface
and scratch the other surface more or less deeply, leading to heating
and welding of the surfaces in question.
Log: Trunk of a felled tree, with the top and branches removed.
Guiding / Alignment: The guiding quality of the chain during its
movement as well as the alignment of the pinions that drive it are
essential aspects. These elements must be checked systematically
before starting up any new equipment.
Play: Space left between two parts that are not perfectly assembled.
Since it is impossible to manufacture parts with perfect geometry,
play is an essential feature when assembling the elements of a mechanism.
Joint: Device allowing a rotary movement to be transmitted between
two shafts in which the relative position is not properly defined,
incorrect or variable.
Rolling mill: Industrial facility used to reduce the thickness of
a material (generally metal). It also allows the production of extruded
bars (long products).
Limit of elasticity: Stress above which a material starts to deform
in an irreversible manner.
Lubrication: It is advisable to grease the return slack strand of
the chain. This allows the lubricant to access the centre of the
chain joint. The quality of the lubricant used and the care taken
when applying it to the chain can substantially affect the behaviour
and service life of the chain.
Link plates: Metal plates linking the joint parts. These can be
roller link plates, in direct contact with the bushings, and pin
link plates, in direct contact with the pin.
Two roller link plates or two pin link plates form a chain link.
Connecting links with self-locking nuts: The two pins are riveted
to a link plate at one of their ends and the other end receives
a connecting link plate immobilised by self-locking nuts.
Connecting links with pinned pins: The connecting link plate is
immobilised by pins to allow easier removal. For certain applications,
we can deliver chains with the pin link plates pinned on one site.
Flat section: Flat surface on a cylindrical part. Hub: Central part
on which the parts that will rotate about an axis are assembled.
It can be offset or symmetrical (wheel with no hub = disc).
Nitriding: Thermochemical treatment leading to the formation of
nitride(s), for hardening the surface of the treated parts.
Pitch: Refers to the distance between two pitch centres with consecutive
axes. The pitch must be selected according to the conditions for
use, the type of product to be transported, the frequency of the
accessories, the available space, etc. Not all pitch values defined
according to a normal series can be achieved: see the table in chapter
2 containing the preferred pitch values. Pitches with intermediate
values or pitches in inches can also be produced.
Shut-down / storage periods: Certain applications may have long
shut-down periods. It is of utmost importance to take every precaution
possible to protect the chain from corrosion by applying a suitable
Link plates with attachments: made by bending or in the shape of
brackets added by welding or by riveting:
o M-shaped attachments with one or more holes, forming an attachment
plane parallel to the link plates.
o K-shaped attachments with one or more holes, forming an attachment
plane perpendicular to the link plates, with the choice of three
centre-to-centre distances for the holes (K2 with short, medium
and long centre-to-centre distance), the width of the attachments
varying accordingly. These attachments can be made on the roller
link plates or on the pin link plates, on one side or both, with
a frequency and arrangement to be specified in the order.
o Special attachments can be made on request for large enough quantities
Polishing: Consists of making a surface smooth and optionally shiny.
Deep link plates: Asymmetric link plates that allow the loads to
be placed directly on the chain rolling over straight rollers. These
chains are generally used in parallel for form a belt and distribute
Perforated link plates: With one, two or three holes, for receiving
attachments or spacer bars. If they pass through the chain, undercuts
will need to be made on the gear teeth of the wheels.
Weight of the table: Total weight of the section in question, i.e.
the entire mobile portion: chain + rollers + pallets + accessories,
Joint pressure: In certain applications, the contact pressure in
the joints is a determining parameter. In fact, this pressure is
responsible, with every oscillation of the chain as it passes over
the wheel, for causing wear of the chain. This pressure must be
monitored, in particular when the chain is used in abrasive environments,
with no maintenance, in stainless-steel chains, etc.
P in N/cm²
F=tangential force in the chain in N
S=projected diametric surface, or Ø of the pin (in cm) x
bushing length (in cm)
The values of P for standard chains can be:
4000 N/cm² with plenty of oil
3000 N/cm² with good maintenance and clean environment
1500 N/cm² with uncertain maintenance and dusty environment
1000 N/cm² without maintenance
Groove: Long notch, with rectangular section, dovetailed or T-shaped,
made in a part.
Performance: Coefficient that takes into account the performance
of the members installed between the motor and the control shaft:
coupler, reduction gear, chain drive, etc.
These coefficients are obviously cumulative. Furthermore, a coefficient
of 1.05 is applied to every new 180° winding. This corresponds
to losses due to the movements of the chain joints, to their placement
on the wheels and to the rotation of the assembly made up of the
wheels and shafts. Minimum tensile strength: It is spread out, according
to a series based on normal numbers, from 20 to 900 kN
Rivet: Permanent assembly element. It is shaped like a cylindrical
rod, generally made of metal, solid or hollow, provided at one of
is ends with a head, in other words, a part with a larger cross-section.
The other end is flattened and widened by crushing, in order to
secure the elements to be riveted together.
Washer: Small pierced disc placed between a screw or a nut and the
part to be clamped in order to transmit and distribute the clamping
force on the part.
Sprocket wheel: Circular member for transmitting movement by means
of the teeth provided on its perimeter. The sprocket wheel transforms
rotation movement into translation.
The wheels used with conveyor chains are made from mechanically
welded steel or cast iron.
The gear teeth are normally foundry mill-cut or flame-cut but, on
request, they can be delivered with trimmed gear teeth, which is
mandatory when using bush chains.
The hubs are offset from the plane of the gear teeth unless the
specifications state the special need for a symmetric hub. The wheels
can be supplied bored and grooved. In the event of inserting a taper
key in the offset hub, the key must enter on the side of the gear
teeth unless specified otherwise.
Roller: Small cylindrical rotating part made from steel that is
very hard, case-hardened or quenched or subjected to any other treatment
and perfectly polished, used in mechanical construction, in bearings.
Rollers protect the bushings and prevent the wear of the gear teeth.
Ball bearing: The purpose of a bearing is to reduce friction between
two rotating parts. Thus, a bearing reduces the heat caused by rotation.
A bearing can also be used to reduce an alignment fault between
Several types of bearing exist: ball bearings, roller bearings,
Silo: A container for storing loose material. Tension: Called "slack
strand adjustment", since a chain should not be tight. This
adjustment makes it possible initially to absorb the joint plays
and then to compensate for lengthening caused by wear. Excessive
tension generates a considerable increase in joint pressure and
leads to premature wear of the chain.
Tolerance: Inevitable inaccuracies of the manufacturing process
mean that parts may not conform strictly to the dimensions established
beforehand in the blueprint. We are therefore required to state
that the dimensions actually produced are comprised between two
limit dimensions, which are compatible with correct operation of
the part. The difference between these two dimensions is what is
known as tolerance.
Wire mill: Continuous rolling train specialised in the production
of machine wire (semi-finished product intended for transformation).
The facility is 300 to 400 m long.
Heat treatment: When applied to a metal part, it consists of causing
the part to undergo structural transformations through predetermined
heating and cooling cycles in order to improve the mechanical features:
hardness, ductility, limit of elasticity, etc.
Hopper: Large stacking hopper intended for storing and then dispensing
a bulk material (grain, sand, etc.) by gravity.
Vibratory finishing: Consists of polishing and deburring techniques.
Its ingredients include abrasive elements (ceramic, porcelain, plastic,
metals), chemical additives and, of course, the devices that generate
the movements (vibrators, centrifuges, etc.). Rafer uses pyramidal
pebbles to clean its mechanical parts.
Fixing screw: Commonly referred to simply as screws, these are mechanical
members which comprise a threaded rod and a head. They are intended
for fixing one or more parts together by pressure.
Galle chains are made up of straight or hollowed-out link plates
and shoulder pins. The shoulders of the pins maintain the separation
between the link plates and allow them to mesh with the pinion.
The chains can have single, double or triple link plates according
to the required tensile strength.
Galle chains can transmit forces ranging from several hundred newtons
to more than one thousand kilonewtons, while their speed should
not exceed 20 m/min.
Galle chains are used for low-speed transmissions (drawing bench)
or to provide to and fro movements (goods lift, dam valves, etc.).
They can therefore be used to transmit considerable forces with
reduced space requirements.
The simplicity of their design allows them to be used for applications
in difficult environments (outdoors, temperature, etc.)
Block chains offer high tensile stress with reduced space requirements.
They can be used for handling heavy or abrasive bodies or when violent
impacts are foreseeable (drawing bench, for example).
To increase the useful life of the chain (improved wear resistance),
the blocks are sometimes bushed
Chain with L-shaped links:
Chain with cast-iron links:
Bush chain: Smooth roller:
Pinned quick attachment:
Attachment with nuts: