Interface Features
Flatness
Bearing mounting surfaces must be machined flat after allwelding and stress relief treatment on the structures iscomplete. If subsequent welding is necessary, it must bedone to avoid distorting the previously machinedmounting surface. The allowable degree of out-of-flatnessin the circumferential direction ( d r ) for typical four-pointand eight-point ball bearings is shown in Figure 3-9. Out-of-flatness, like distortion, must be gradual, reflecting asinusodial wave pattern and not occur in a span less than90° and not more than once in 180°.In addition to flatness in the circumferential direction, the
allowable dish or perpendicularity deviation ( d p ) in theradial direction must be determined. For ball bearingdesigns, this can be done using the following equation.
d p ≈ 0.001 • D w • P
Where P = radial distance of mounting structure faceThe allowable degree of out-of-flatness for roller bearings is2/3 the limit for an equivalent-sized four-point ball bearing.It may be necessary to reduce the d r and d p values inapplications which require low rotational resistance or highprecision.



LYDZC offers the following guidelines to assistdesigners. Failure to follow any of these may causeadditional risk and/or premature failure. Therefore, testingof the overall configuration and bearing installation isrequired to validate the design. Extra caution is requiredduring any testing, as failure of any component could leadto complete separation. This may result in injury or fatalityto anyone in close proximity.
A uniform vertical and tube-shaped structure with a flange on one end should be used, allowing adequateroom for fastener installationandmaintenance. Thisstructure would be similar to the end of a flanged pipewith a diameter close to that of the bearing's raceway.
Refer to Figure 3-5. For initial sizing, wall thickness ofsuch tubing should be at least 1/5 the overall height ofthe adjacent bearing's ring. Refer to Figure 3-4.The mounting or structural plate supporting the bearing should have a finished thickness of 1/2 of thebearing ring height for single-row rolling elementbearings and at least 1/3 of the bearing ring height formulti-row bearings. Generally, thinner mounting platesrequire more structural support and bracing to stiffen