Page 148 - Rollingbearings

B.6 Bearing interfaces
Tolerances for seats For shaft diameter ratios c > 0,5 the diam­ • The diameter ratio of the bearing inner
i
on hollow shafts eter tolerance determined for a seat on a ring is
solid shaft should be adjusted to achieve the
same effectiveness of the it on the hollow
When a bearing is mounted on a hollow shaft. This can be done with the following c = JJJJJJJ 40 = 0,77
e
shaft using an interference it, the shaft procedure. 0,3 (80 – 40) + 40
experiences more elastic deformation than a
solid shaft. As a result, the effectiveness of 1 Determine the mean probable interfer­ • The mean probable interference on a solid
the it is less than for the same size solid ence for the tolerance selected for a seat shaft is
shaft. The effectiveness of an interference it on a solid shaft, Δ (Tolerances and result- Δ = (22 + 5) / 2 = 13,5 μm (table 14,
S
S
on a hollow shaft depends on certain diam- ant its, page 153). page 160, k5 for a 40 mm shaft diameter)
eter ratios (ig. 5): 2 Determine the required increase of inter­
ference for the seat on the hollow shaft • The increase in interference for the seat
• the diameter ratio of the hollow shaft from diagram 1, based on the diameter on the hollow shaft is
c = d / d ratios c and c . Δ / Δ = 1,7 (diagram 1, c = 0,8 and
i
i
e
S
i
i
H
For diameter ratios c ≤ 0,5 the reduc­ 3 Calculate the required mean probable c = 0,77)
i
e
tion of effectiveness is negligible. interference for the seat on the hollow
• the diameter ratio of the bearing inner shaft and select the tolerance class • The requisite interference for the seat on
ring c = d / d e accordingly. the hollow shaft is
e
When the average outside diameter of Δ = 1,7 × 13,5 = 23 μm
H
the inner ring d is not known, the diam­ Example
e
eter ratio can be estimated from • The appropriate tolerance class for the
A 6208 deep groove ball bearing with seat on the hollow shaft is m6 (table 14,
d = 40 mm and D = 80 mm is to be mounted mean probable interference,
d
e on a hollow shaft with a diameter ratio (33 + 13) / 2 = 23 μm)
k (D – d) + d
c = JJJJJ
c = 0,8. What is the appropriate tolerance
i
class for the shaft seat?
The bearing is subjected to normal loads,
where and a tolerance class k5 is appropriate for a
Bearing interfaces d = bearing bore diameter [mm]
c = diameter ratio of the bearing inner
seat on a solid shaft.
e
ring
D = bearing outside diameter [mm]
k = adjustment factor
= 0,25 for self­aligning ball bearings in
the 22 and 23 series
B.6 = 0,25 for cylindrical roller bearings
= 0,3 for other bearings
Diagram 1
Relationship of interference Δ H , needed for a hollow steel shaft, to the known interference Δ S
for a solid steel shaft
Fig. 5
Δ H / Δ S
Seat on a hollow shaft 2,0

1,8
ce = 0,7
1,6

1,4
d i d d e 0,8
1,2
0,9
1,0
0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9
c i

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