to axial clearance
First it is necessary to determine the zero clearance condition as accurately as possible. This is rather difficult for taper roller bearings on horizontal shafts, as the weight of the shaft and gears displaces the outer rings axially because of the taper angle, so that the clearance-free roller end/flange con- tact, which is decisive for the adjust- ment, is difficult to achieve. The pro- cedure described in the following is well proven and is very much simpler and more reliable. A device is used to swing the gear shaft into the vertical position for the adjustment (➔ fig ).
● Mount the inner rings on the shaft (take care that the rings abut the shoulders correctly).
● Push the outer rings over the roller and cage assemblies.
● Place the shaft with bearings in the gearbox which should be horizont- ally positioned
● Mount the top of the casing.
● Screw down the cover at one side of the casing.
● Tilt the casing so that the shaft is supported via the bearing by the cover.
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● Rotate the shaft by hand (if neces- sary by turning the input or output shaft) and press the outer ring of the upper bearing downwards in its seat- ing until all the rollers in the bearing turn about their own axes. The bear- ing arrangement is now free of clear- ance.
● The requisite length of the spigot in the cover is determined from a = x – s where s is the required axial clearance.
● Mount the finish machined cover with shims (if necessary).
The weight of the shaft and gears acts as a measuring load on the lower bearing. The upper bearing is free of clearance as soon as all the rollers rotate about their own axes when the shaft is rotated.
A limited range of matched single row taper roller bearings (DF execu- tion) is available. The bearing pairs are supplied with an appropriate interme- diate ring, so that adjustment is not required. The user can also match single row taper roller bearings him- self; the requisite width of the interme- diate ring, taking into consideration the fit, is determined as follows.
● Mark the bearing components as shown in fig using an electric pen.
● Place bearing A on three gauge blocks (➔ fig ).
● Apply the measuring load:
300 N for bearings with outside dia- meter up to and including 240 mm 500 N for bearings with outside dia- meter over 240 mm.
● Turn outer ring 1A by hand so that the rollers abut the flange of the inner ring 1A.
3 2 Fig 1 Fig 2 Adjustment of taper roller bearings arranged face-to-face with axial clearance Marking of bearing components
Bearing bore Shaft Maximum standard axial clearance ∆abefore mounting diameter tolerance d Bearings of series over incl. 329 320 X 330 331 302,322 332 303,323 313 (X) mm – mm – 30 k5 – 0,120 – – 0,140 0,150 0,170 0,100 30 40 k5 0,200 0,140 – 0,160 0,160 0,170 0,180 0,110 40 50 m5 0,220 0,160 0,220 0,180 0,180 0,170 0,200 0,120 50 65 m5 0,250 0,180 0,240 0,200 0,200 0,190 0,220 0,140 65 80 m5 0,270 0,200 0,290 0,240 0,220 0,220 0,260 0,170 80 100 m5 0,310 0,230 0,390 0,270 0,270 0,260 0,300 0,170 100 120 m5 0,330 0,280 0,400 0,300 0,280 0,300 0,340 0,190 120 140 m5 0,370 0,300 0,400 – 0,300 – 0,390 0,220 140 160 n6 0,430 0,330 0,400 – 0,330 – 0,430 0,240 160 180 n6 0,430 0,370 – – 0,370 – 0,450 – 180 190 n6 0,430 0,400 – – 0,400 – 0,500 – 190 200 n6 0,450 0,400 – – 0,400 – 0,500 – 200 225 p6 0,500 0,450 – – 0,450 – 0,550 – 225 250 p6 0,500 0,500 – – 0,500 – 0,600 – 250 280 p6 0,600 0,550 – – 0,550 – – – 280 300 p6 0,700 0,600 – – 0,600 – – – 300 340 p6 0,700 0,650 – – 0,650 – – – 340 360 p6 0,750 0,750 – – – – – –
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● Measure the standout FAat three points using the gauge blocks.
● Calculate the average value of FA from
FA1+ FA2+ FA3
FA = (mm)
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● Repeat the above procedure for bearing B.
● Calculate the average value of FB from
FB1+ FB2+ FB3
FB = (mm)
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● Determine the width of the interme- diate ring from
C = FA+ FB+∆a(mm)
where∆a= maximum axial clearance according to Table or for special bearings, the maximum value of the special clearance.
The following tolerances apply to the width C of the intermediate ring: 0/–0,04 mm for bearings with outside diameter D ≤ 140 mm and 0/–0,06 mm for berings with outside diameter D > 140 mm
The axial clearance values given take into account the clearance reduction caused by the interference fit when the shaft tolerances (also given in Table
) are applied. These tolerances are required for rotating inner ring loads which are moderate to heavy. The outer ring with its point load should have a seating to tolerance J6 or H7.
1 1 111 Measuring the standout F Maximum stand- ard axial clearance of matched taper roller bearings F Fig 3 Table 1 Measuring load Gauge block
S
Principle of force/path measurement
Recorded force/ path diagram for shaft/bearing/ housing system
There will be virtually no reduction in clearance from any deformation of the outer ring. If looser fits are chosen, then the axial clearance value will be slightly larger when the bearing is mounted. If a tighter fit is used then it is advisable to check that the bearing will not be axially preloaded.
Adjustment of taper roller
bearings arranged face-to-face
to preload
When adjusting bearings which are to have a preload it is necessary to achieve a certain preload force. If the preload distance (path) method is to be used, it is first necessary to meas- ure the force and displacement in the mounted condition. This is the only way to be able to take housing resili- ence into account when determining the appropriate distance. Fig shows the principle of a force/distance measure- ment. Diagram shows the result of such measurements. The characteris- tic curve has been extrapolated (brok- en line) for small loads because the measurements are not sufficiently accurate under such light loads. Using the characteristic curve the desired preload can be set by fitting a shim or spacer ring.
The adjustment of taper roller bear- ings using the friction torque as a
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basis or a collective method based on tolerances has not found acceptance in gearbox applications as there is excessive scatter of the preload force when these methods are used. However, the friction torque can be used indirectly for adjustment as will be seen from the following.
● The friction torque of the two bear- ings which are to be adjusted against each other is measured in a rig for a given preload force and at a defined measuring speed and recorded.
● After mounting the bearings in the gearbox, the preload force is applied by inserting shims until the recorded friction torque is obtained. The speed and lubrication conditions when the torque is measured must be the same as when the original recorded measurements were made. This method is advantageous particu- larly when large numbers of bearings are to be adjusted if it is easier to measure torque than force at the assembly position.