Page 45 - needle bearings

Lubrication
NTN

Table 8.2 Grease varieties and characteristics
Calcium
Sodium grease Aluminum
Grease name Lithium grease compound base Non-soap grease
(Fiber grease) grease
grease
Ca+Na soap Bentone, silica gel, urea,
Thickener Li soap Na soap Al soap
Ca+Li soap carbon black, etc.
Base oil Mineral oil Diester oil Silicone oil Mineral oil Mineral oil Mineral oil Mineral oil Synthetic oil
Dropping point ˚C 170ʙ190 170ʙ190 200ʙ250 150ʙ180 150ʙ180 70ʙ90 250 or more 250 or more
Operating
˚C ʵ30ʙʴ130 ʵ50ʙʴ130 ʵ50ʙʴ160 ʵ20ʙʴ130 ʵ20ʙʴ120 ʵ10ʙʴ80 ʵ10ʙʴ130 ʵ50ʙʴ200
temperature range
Mechanical stability Excellent Good Good Excellent to good Excellent to good Good to poor Good Good
Pressure resistance Good Good Poor Good Excellent to good Good Good Good
Water resistance Good Good Good Good to poor Good to poor Good Good Good
Broadest Excellent in low suited to high emulsified by Excellent in water Excellent in Available for use in wide temperature
application. temperature temperature and inclusion of water resistance and viscosity range from low to high temperature.
characteristic and low temperature. content. mechanical characteristic. Some of non-soap base greases are
Grease for anti-friction stability. excellent in heat resistance, cold
Applications universal type characteristic. Low oil film Comparatively Suitable for resistance, chemical resistance, etc.
rolling bearings. strength and excellent in high Suitable for bearing subjected subject to proper combination of base
unsuitable for temperature bearing subjected to vibration. oil and thickener.
high load characteristic. to shock load. Grease for universal type rolling
application. bearings.
Remarks: The operating temperature range in this table is the general characteristic value, not the guaranteed value.

8.1.4 Additives Table 8.3 Grease consistency
Any greases contain various additives to improve the NLGI JIS (ASTM)
60-cycle mixed
performance, for example, containing oxidation inhibitor, consistency No. grease consistency Application
extreme pressure additives (EP additives), rust inhibitor,
0 Soft 355ʙ385 For centralized greasing
corrosion inhibitor, etc.
A grease containing extreme pressure additives is used 1 310ʙ340 For centralized greasing
for bearings subjected to high load or shock load. A 2 265ʙ295 For general application, for tight-sealed bearing
grease containing oxidation stabilizer is used for bearing 3 220ʙ250 For general application, for high temperature
applications wherein the operating temperature is
4 Hard 175ʙ205ɹ Special application
comparatively high and no grease is replenished for a
long time.

8.1.5 Consistency
"Consistency" is an index showing the hardness or 8.1.7 Grease fill amount
fluidity of grease. The greater numerical value thereof is Grease fill amount differs depending on housing
the softer hardness. This consistency is determined by design, spacing volume, rotational speed, kind of grease,
the amount of thickener and the viscosity of base oil. etc.
Usually NLGI consistency codes 1 and 2 or 3 are used for Around 50% to 80% of static spacing volume in bearing
lubrication of bearings. and housing is deemed as a guideline to the fill amount.
Table 8.3 shows the general relationship of grease In the case of high rotational speed, this fill amount must
consistency to application. be set up a little bit less for controlling temperature rise to
a low rate. Too much fill amount of grease would
8.1.6 Grease mixing cause the grease temperature to rise higher, which
When different greases are mixed together, the would then lead to reduction of the specific
consistency of the mixed grease varies (generally lubrication performance due to leak of the softened
softens) so that the allowable operating temperature gets grease or quality change such as oxidation, etc.
lower. To avoid such characteristic variation of grease, it Further, for the machined ring needle roller bearing with
is not allowed to mix different greases, except mixing inner ring the approximate value of spacing volume in the
greases of same brand. bearing can be determined by formula (8.1).
Where mixing of different greases is inevitable, greases
Vʹ35W ⋯⋯⋯⋯⋯⋯⋯⋯⋯⋯⋯⋯⋯⋯⋯⋯(8.1)
composed of thickener of same kind and similar base oil must
be selected. Even when greases of same kind are mixed where,
together, thus, the properties of the mixed grease could vary V : Internal spacing volume (approximate value) cm 3
depending on difference in additives, etc. It is therefore W : Bearing weight kg (See Dimensions Table)
necessary to check the property variation in advance.

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