“Reading” and “Measuring” of Bearing Tolerance

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“Reading” and “Measuring” of Bearing Tolerance

The product sections for the various bearing types provide information on compliance with applicable tolerance classes. High precision oilless bearings with maximum speed suitability。Benefits for our customers: High durability, high operating safety.

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Reading & Measuring Bearing | Viiplus

“Bearing tolerance refers to the shape, size, position relationship of the object, etc., and “tolerance” is “allowable error”. It also includes defining dimensions, defining allowable errors in shape and position.

What is bearing tolerance

“The marking method of design drawings can be roughly divided into the length, shape, parallelism, inclination, position and run-out of each part..”

Marking method of design drawing

On the basis of dimension information, bearing tolerance information such as “parallelism” and “flatness” is added. In this way, problems caused by simply marking dimensional tolerances can be avoided. Correctly and efficiently convey designer intentions that cannot be reflected through dimensional tolerances.

Advantages of bearing tolerances

Measurement with different measuring equipment and detection methods. For example, the distance between two points will be measured with a vernier caliper, micrometer, etc., and the roundness and the position of the central axis will be tested with a roundness measuring instrument and a coordinate measuring instrument.

Method of measurement

ISO is a stated international standard. However, in the United States and other countries, some enterprises may follow ASME (American Society of Mechanical Engineers) guidelines that do not apply the principle of independence. Therefore, when conducting trade with overseas enterprises, it is recommended that the specification requirements must be clarified through negotiation and other channels in advance.

ISO Standards

“Thoroughly understand bearing tolerance symbol and control significance, and understand its concept correctly.”

Focus on Bearing Tolerance

What is a benchmark

The so-called datum (datum) is the surface, line and point used as the datum when processing and dimensional measurement. Benchmarks are divided into “benchmark elements” and “simulation benchmark elements”. There is also a benchmark system that combines more than two benchmarks and designates elements.

  • Benchmark elements

    The actual elements of the object (surfaces of components, holes, etc.) are used to set the benchmark.

  • Analog reference element

    An actual surface (plate, bearing, mandrel, etc.) of extremely precise shape in contact with the reference element when setting the reference.

  • The benchmark system

    In order to establish a baseline with tolerance elements, a baseline group of two or more different benchmarks is used in combination.

    Surfaces of parts labeled as datum do not have perfect shape. Therefore, it is necessary to contact the plate, ruler, mandrel, etc. with more precise surface as a practical reference.

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Datum can be annotated by a datum symbol. Reference symbols are marked by hollow or blackened triangles. The letter representing the reference must be in the same direction as the drawing.

In addition, the area of the object will vary depending on the position of the reference symbol in the drawing. In order to convey the design intent carefully, please note the position of the marking reference.

  • Marking axis or central plane

    Combine dimension line with datum at one place to mark datum element. The labeled datum element center will become the datum axis or datum central plane.

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Types Of Bearing Tolerances

  • Shape tolerance (shape deviation)

    The so-called shape tolerance is the basic geometric tolerance that determines the shape of the object (part). The geometric tolerances of shapes can be determined independently without datum.

  • Shape tolerance, position tolerance (line profile, surface profile)

    Line profile and surface profile are also used for position tolerances. The marking method of shape control frame in shape tolerance and position tolerance is the same.

  • Attitude tolerance

    The so-called attitude tolerance is the tolerance that determines the attitude of the corresponding element relative to a certain datum. Before specifying the attitude tolerance, the datum must be determined, so the attitude tolerance is the element associated with the datum, that is, the geometric tolerance of the associated element.

  • Position tolerance

    The so-called position tolerance is the tolerance that determines the position (true position) of the corresponding element relative to a datum. The datum must be determined before the positional tolerances can be specified, so the positional tolerances are the elements associated with the datum, that is, the geometric tolerances of the associated elements.

  • Runout tolerance (runout deviation)

    The so-called “runout tolerance” is the geometric tolerance that controls the runout variation of the target element by setting a certain straight line as the rotation axis, rotating the target object (component). Before the runout tolerance is specified, the datum must be determined, so the runout tolerance is the element associated with the datum, that is, the geometric tolerance of the associated element.

Shape Control Frame

Bearing tolerances are marked by “shape control frame”. The shape controller enclosure should contain the following elements.

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  • Maximum Entity Requirements (MMR) vs. Minimum Entity Requirements (LMR)

    MMR: Maximum Material Requirement (MMR) is used to mark the tolerances of embedded components such as shaft holes. The LMR: Least Material Requirement is used to specify the strength of the hole around the end face and the thickness of the pipe.

Classification And Notation Of Geometric Tolerance Characteristics

size

Specifies the “straightness” parameter that indicates how correct the straightness should be. Applies to a straight line rather than a flat object and represents the bending of centerlines, busbars, etc. Therefore, it can be used to set the allowable warping of objects with long dimensions.

Specify “surface convexity” to indicate what the correct flat surface should be. The most raised part and the most depressed part must be located at a certain distance between the upper and lower separated planes.

Specifies the roundness parameter. Indicates the roundness of a circular section such as a shaft, hole, cone, etc., indicating what the correct circle should be.

Specifies the roundness and straightness parameters. Indicate the distortion of the cylinder and indicate what the correct cylinder should be.

This is a parameter that indicates whether the actual surface of the design component is consistent with the design ideal value, and represents the distortion of the contour (the line element presented by the surface cut surface). The section line that cuts off the specified surface must be within the tolerance zone.

Mark the parameters of the design component “whether the actual surface (surface) is consistent with the design ideal value”. Surface profile differs from line profile in that it takes the entire surface as an object.

Similar to flatness, parallelism has datum (plane, line). Parallelism specifies “the degree to which two lines or planes are parallel to each other.”

Specifies the “degree of right-angle correctness” relative to the datum (the plane, line that serves as the datum). The unit of the value specified by a straight Angle is not Angle, but mm.

If the specified line or plane is not 90°, specify whether it is properly tilted with respect to the datum (the plane or line used as the datum). Gradients are specified in mm rather than in Angle.

Specifies the accuracy of the “degree of positional correctness relative to the datum”.

Specifies “the degree to which the axes of the two cylinders are coaxial (with no deviation from the central axis)”.

Specifies the precision of “the degree of axis alignment (no deviation at center point) of 2 cylinders”. The difference from coaxiality is that the reference element is the central point (plane).

Specifies the accuracy of maintaining “symmetry with respect to the datum (the plane that serves as the datum)”.

Specifies the “jump of any circumferential part of a rotating part”. Circular runout — that is, the measured runout of rotating parts must be within the specified range.

Specifies the “jump of the entire surface as it rotates” of the part. Total runout — that is, the runout of the whole measured value of the cylinder must be within the specified range.

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