Page 227 - Rollingbearings

Bearing execution
Bearing interfaces Bearing execution

Intial internal clearance
The bearing inner rings have a stationary load condition and no
spacer between the inner rings in the cross-located arrangement
They are mounted with a loose it for easy mounting. The recom- The current design uses bearings with Normal initial clearance. The
mended it for standard conditions is g6� (table 5, page 148). interference it on the outer ring reduces the internal clearance. We
The outer rings have a rotating load condition, so they are determine the operational clearance for both Normal and C3 initial
mounted with an interference. The recommended it for standard clearance, to select the most appropriate bearing execution
conditions is M7� (table 8, page 151), which has a prob able inter-
ference range of –25 to +8 (table 20, page 172). 1. Initial internal clearance
Bearings in rope sheaves of paper machines should always have Refer to Bearing data, page 250 Values obtained from table 6,
an interference for the outer ring (application handbook Rolling bear- page 252
ings in paper machines). To achieve this select N6�, which has a
probable interference range of –29 to –5 (table 21, page 174). For Normal C3
geometrical tolerances and surface roughness, standard recommen-
dations can be applied.
The tolerances for the bearing seats are: min /avg /max 6 / 13 / 20 μm 15 / 24 / 33 μm

Dimensional Total radial Total axial Ra 2. Clearance reduction caused by interference its
tolerance run-out run-out
tolerance tolerance There is no interference on the inner ring, therefore use:
Δr = Δ f (Clearance reduction caused by interference its, page 184)
2 2
it
Inner ring g6� IT5/2 IT5 1,6 µm
Outer ring N6� IT6/2 IT6 3,2 µm Obtain values for:
• factor, f (diagram 2, page 184)
2
• probable its for housings, Δ (table 21, page 174)
2
)
Results:
d/D 0,49
f 2 0,87
Δ 2 min /avg /max –29 / –17 / –5 μm
min /avg /max –25 / –15 / –4 μm
Δr it
3. Internal clearance after mounting

Normal C3

min /avg /max –19 / –2 / 6 μm –10 / 9 / 29 μm

At least C3 clearance is required Analysis with SKF proprietary
software, considering the effects from smoothing of the mating sur-
faces and the probability that maximum it reduction coincides with
minimum bearing clearance, provides the following values for a
bearing with C3 internal clearance:
C.2 Rope sheave
min /avg /max –2 / 16 / 32 μm

A small negative clearance is not critical for ball bearings C3 clear-
ance is adequate for this application

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