NTN - Precision Rolling Bearings
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Technical Data<br />
1 Grease lubrication<br />
Grease lubrication is the most common, as it<br />
simplifies the main spindle structure more than other<br />
lubricating systems. With an adequate amount of<br />
quality grease prefilled, this system can be used over a<br />
wide range of speed. The allowable maximum speed<br />
varies with the type and size of bearing: for a highspeed<br />
angular contact ball bearing, the dmn value<br />
should be 1.410 6 as a guideline. For applications<br />
exceeding this range, consult <strong>NTN</strong> Engineering.<br />
Grease types<br />
A lithium-based grease, with a mineral oil base, is<br />
commonly used as a lubricant for rolling bearings. Its<br />
operating temperature range is -30˚C to 130˚C.<br />
When the temperature increase must be limited, as<br />
with the main spindle of a machine tool, <strong>NTN</strong><br />
recommends the use of a synthetic-oil-based grease<br />
(diester, diester+mineral oil) which penetration is NLGI<br />
grade 1 or 2.<br />
Table 7.3 lists technical data for greases commonly<br />
used for machine tool main spindles.<br />
Amount of grease required<br />
Usually, a bearing for the main spindle of a machine<br />
tool requires that grease volume be low so heat<br />
generated by the stirring of the grease during highspeed<br />
operation is minimal. A guideline for the amount<br />
of grease used for a main spindle bearing is given<br />
below.<br />
¡Angular contact ball bearing<br />
(dmn value 65010 3 ); 15% of bearing free space<br />
(dmn value 65010 3 ); 12% of bearing free space<br />
¡Cylindrical roller bearing; 10% of bearing free space<br />
¡Tapered roller bearing; 15% of bearing free space<br />
The space in the bearing typically used for main<br />
spindles are listed in dimension tables. Determine a fill<br />
amount by referring to the relevant dimension table.<br />
Before filling a bearing with grease, remove the<br />
rustproof coating from the bearing with clean wash oil<br />
and allow the bearing to dry completely. Then fill and<br />
uniformly distribute an appropriate amount of grease in<br />
the bearing with an syringe, plastic bag, etc.<br />
Table 7.3 Typical greases for machine tool main spindle bearings<br />
Grease brand<br />
SE-1<br />
MP-1<br />
ISOFLEX<br />
NBU15<br />
Stabllugs<br />
NBU 8EP<br />
Multemp<br />
LRL3<br />
Multemp<br />
PS2<br />
ISOFLEX<br />
LDS18<br />
Thickener<br />
Urea<br />
Ba complex soap<br />
Li soap<br />
Base oil<br />
Ester<br />
Synthetic oil<br />
Ester<br />
Mineral oil<br />
Synthetic oil<br />
Diester+mineral oil<br />
Synthetic oil<br />
Base oil viscosity<br />
<br />
(40˚C) mm 2 /S<br />
22<br />
40.6<br />
20<br />
105<br />
37.3<br />
15.3<br />
16<br />
Dropping point<br />
˚C<br />
220<br />
254<br />
200<br />
220<br />
208<br />
190<br />
180<br />
Operating<br />
temperature range<br />
˚C<br />
Application<br />
50120<br />
Applied to ULTAGE<br />
Series grease-lubricated<br />
sealed angular contact<br />
ball bearings<br />
40150<br />
Applied to ULTAGE<br />
Series grease-lubricated<br />
sealed angular contact<br />
ball bearings<br />
60130<br />
Most commonly<br />
used for main<br />
spindles<br />
35150<br />
Suitable for roller<br />
bearings subject<br />
to large loads<br />
40150<br />
Wider operating<br />
temperature range<br />
55130<br />
Excellent low<br />
temperature and<br />
friction characteristics<br />
60130<br />
Suitable for ball<br />
bearing<br />
<strong>NTN</strong><br />
grease code<br />
L749<br />
L448<br />
15K<br />
L135<br />
12K<br />
1K<br />
6K<br />
40
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