Page 14 - Industrial Technology January 2020

DESIGN ENGINEERING
THIN SECTION BEARINGS
“ tight, weight must be minimised and absolute precision. various materials choices, finishing processes and roller-
ON A LARGER BEARING WITH A
BORE OF AROUND 900MM THE
WEIGHT SAVING COULD BE IN
THE REGION OF 400KG.
SERIOUS NUMBERS
Author Mike Page is sales manager at
Carter Manufacturing
MORE INFORMATION: www.carterbearings.co.uk • sales@carterbearings.co.uk • Tel: 01865 821720 suitable.
14
BEARINGS, SLIDES AND LUBRICANTS
MIKE PAGE EXPLAINS WHY THIN SECTION BEARINGS SHOULD BE ON
EVERY DESIGN ENGINEER’S RADAR WHERE SPACE IS TIGHT, WEIGHT
SAVING IS REQUIRED AND WHERE TOLERANCES ARE EXTREME
hin section bearings offer design engineers a include thin-dense chrome which helps to extend service
unique combination of advantages in a single, life, delivers even smoother running and assists in
hard wearing and lightweight package. As the combating corrosion.
Tname implies, they are significantly thinner in Designers can choose between three definitive types of
section than ‘ordinary’ rotating bearings and possess thin-section bearing, dependent upon their application
attributes that make them very different from ordinary requirements, with each of them delivering a different set
radial bearings. One of the most important (and useful) of of advantages. Radial contact by the balls may be
these is that whereas most radial bearings are designed so preferred for some uses, whereas the alternatives of either
that the bearing thickness increases proportionately as the angular or four-point contact might be preferred for others.
bore size gets bigger, in the case of thin-section bearings, Likewise, designers can make choices regarding ball types
the thickness remains fixed even though the bore size (including ceramic balls) together with different cage
increases. designs, alternative materials options and a variety of
Generally, thin-section bearings are specified for use in lubrication choices. On some thin-section bearings,
critical applications and environments where space is special seals and/or retainers can be manufactured too.
The combination of thin-section size preferences, the
In these types of application, thin section bearings have
helped to reduce the total cost in a system by allowing for
discussions on the sort of projects in which these bearings
design efficiency over standard bearing sizes, with the contact types and materials are all vital elements in early
added advantage of using just a single bearing which excel.
shows little change in its weight even as its diameter
increases. Lubrication considerations
Speaking of weight saving, the advantages offered by As with all bearings, lubrication is an essential element
thin-section bearings in this respect can be substantial. that should be considered in advance, and OEMs
For example, on a bearing with a bore of 100mm, a thin- invariably choose one of the three lubricant types which
section bearing might weigh 1kg less than a standard are most commonly used: oil, grease, and dry film or
option. And on a larger bearing with a bore of around surface treatment. Oil normally provides better lubrication
900mm the weight saving could be in the region of because it covers critical surfaces more thoroughly and
400kg. Serious numbers. However, when designing with dissipates heat more rapidly, whereas grease is clearly
thin-section bearings, engineers should always remain more easily retained, allowing the use of simplified
aware that they can be affected by the tolerance, bearing housings and seals.
roundness, and expansion and contraction rates of the It should be noted that in addition to ‘standard’
housing and shafts used to mount them. The range of lubricating oils and greases, leading thin-section bearing
temperatures in which thin-section bearings will typically manufacturers can also offer vacuum-compatible oils and
operate is –52°C to +120°C. greases, as well as dry film lubricants alluded to
Thin section bearings can be manufactured in a variety previously, including graphite, tungsten disulphide, silver,
of materials, with 52100 vacuum-gassed chrome steel lead, PTFE and molybdenum disulphide to assure lengthy
and 440C martensitic stainless steel being amongst the and trouble-free thin-section bearing service life.
most popularly specified, although 17-4PH and M50 tool
steel can also be specified. As with many other types of Coping with undesirable loads
bearing, thin-section bearings can also be specified with Unwanted moment loads can be the design engineer’s
a variety of specialist coatings if required. Examples enemy, and in the combating of unwanted axial or radial
loads, thin-section bearings have been proven to excel,
partly because they are designed from the outset to cope
with it. Project designs which are expected to generate
significant moment loads but which also have critical
space and weight-saving requirements (to say
nothing of the need for cost-reduction) often see
the maximum benefit from the use of a single,
thin-section bearing rather than paired standard
bearings. This is because the thin-section design
delivers inherent resistance to moment load, so
the lifespan of a critical bearing can be greatly
enhanced if a thin-section type is deemed
INDUSTRIAL TECHNOLOGY • January 2020