CHIARAVALLI
STRAIGHT
SPUR GEARS
AND RACKS
Straight gears and racks are the classical components for
mechanical transmission of rotary and transverse movements
between moving parts of machines.
This explains why these components are so widespread and
are used to such a large extent in various sectors of general
mechanics such that in practice it is impossible to find a rigid
type power transfer drive chain which does not adopt these
basic components.
However, the needs of industry are extremely complex as re-
gards the performance required from the gear and the rack
and reflect the typical operating conditions in terms of preci-
sion or resistance of final use for which the gear and the rack
are designed. This is why proposing a product intended to
meet any need expressed by industrial experience would be
unthinkable.
CHIARAVALLI GROUP SpA has made a basic choice with this
aspect in mind, deciding to offer industry a broad range of
gears and racks for general use, combined in a standardised
series, which is characterised by excellent quality.
The gears and racks produced using standardised C40 steel
are manufactured adopting modular sizes in accordance with
a reference profile that complies with
DIN 3972
II and a full head radius.
This ensures complete engagement at the base of the tooth
with an obvious increase in the bending resistance.
The internal specifications that define the geometry of the
tooth prescribe a marked “K” profile for the side surface,
with a strict limitation of the profile errors to negative devia-
tions. This has a positive influence on the level of noise of the
toothed pair, since the engaging impacts to the teeth head
are reduced.
The systematic use of latest generation CNC gear hobbing
machines, special hobs designed for very high cutting spe-
eds and specifically developed processing technologies,
enable a general precision to be assured in compliance with
DIN 3962
Standards and a degree of surface finish that is not readily
achieved with operations using a hob gear cutting machine.
The working tolerance for tooth thickness has been chosen
to comply with the
“cd 25” Coupling Category
in accor-
dance
with
DIN 3967
Standards,
which defines the position and the size of the tolerance ran-
ge and therefore the coupling gap between the gears.
A processing
tolerance equal to “js 8”
for the centre distan-
ce is recommended in compliance with
DIN 3964
Standards
for normal operating conditions, which if adopted, enables
us to assure a minimum working coupling gap of adequate
size, while at the same time limiting the value of the ma-
ximum gap. Similar considerations apply in the case of the
gear-rack coupling, since the latter is manufactured adopting
the same coupling category.
Our Technical Department is available and willing to recommend
the most appropriate assembly tolerances to Customers who are
interested, although we are also able to manufacture gears with
coupling gaps that are larger or smaller compared with the stan-
dard value to meet specific needs.
We are able to manufacture our straight gears as illustrated in the
catalogue with a lengthwise crowning of the teeth, at the request
of customers. This solution is particularly useful if the user is unable
to ensure a perfect alignment between the axes.
THE RANGE OF MACHINES USED, COMPRISING ALMOST
ENTIRELY OF VERY MODERN MACHINES THAT HAVE CUTTING
EDGE FEATURES AND DESIGN ENABLES OUR COMPANY TO
PRODUCE GEARS BASED ON A DRAWING IN QUALITATIVE AT
A VERY COMPETITIVE PRICE.
Our Technical Department is available to carry out a preliminary
examination of any processing problems experienced by
Customers and to prepare cost estimates.
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