2023 June the First Week KYOCM Technical Knowledge: Improvement of Measurement Method for Verification of Bearing Groove Position

Abstract: The original method for verifying the position of ball bearing grooves has limitations, especially for complex shaped rings, it is more difficult to measure the position of grooves. In response to this situation, improvements have been made to the original measurement method, improving its applicability, measurement efficiency, and accuracy. Not only can it be applied to standard parts for verifying groove position, but it can also be used to directly measure the groove position of certain special groove shaped parts on the processing site.

Keywords: Rolling bearings; Channel location; Measuring instruments; Standard parts; improve

During the machining and inspection process of ball bearing grooves, the position of the groove is one of the important detection items, and usually instruments or templates are used for comparative measurement. The instrument measurement method is mainly carried out on instruments of the same types as DO12 (outer groove) and D022 (inner groove). During measurement, one position standard piece needs to be calibrated in advance as a comparison sample. The verification of position standard parts requires the use of height standard parts for indirect measurement. Although this verification method is simple and feasible, it has defects such as not fully ensuring measurement accuracy and difficulty in measuring bearings with special structural shapes. Therefore, it is necessary to improve this calibration method to improve measurement accuracy and expand its application range.

1. Original calibration method

The original calibration method is shown in Figure 1. Before measurement, first select one steel ball of the same size as the finished bearing and one height standard part, so that the sum of the steel ball radius Dw/2 and the height value h of the height standard part is close to the position value H of the bearing channel.

Firstly, measure the total height H1 (H1=h+Dw) of the steel ball and height standard component, and make the measuring needle indicate a measurement point in the middle of its range as the reference zero point; Then, move the steel ball to the bottom of the bearing groove, adjust the bearing ring and steel ball so that the instrument needle contacts the highest point of the steel ball, check the position indicated by the needle, and record the actual height value as H2 at this time; The difference between the two indicated values is recorded as δ = ∣H1-H2∣(when H1>H2, take "-"; when H1<H2, take "+"), then the actual channel position H=H1-Dw/2 ± δ =  H+Dw/2+H2-H1.

The above calibration method is simple and easy to operate, but there are certain problems: (1) due to the steel ball radius being smaller than the groove curvature radius, the positioning of the steel ball is prone to instability and deviation in actual operation, resulting in measurement errors; (2) For measurements of irregular groove shapes and positions (such as asymmetric grooves in angular contact bearings and non-standard bearing parts with deeper groove shapes), it is difficult for steel balls to accurately locate them; (3) The tip surface of the testing instrument is too small, making it easy to swing during the measurement process, making it difficult to accurately locate the highest point of the steel ball by directly contacting the surface of the tested object. From this, it can be seen that this method has problems of inconvenient operation and low measurement efficiency, requiring high technical level and experience of operators, and is prone to human measurement errors, which need to be improved.

(a) Step 1

(b) Step 2

1- Measurement platform; 2- Samples to be inspected; 3- Height standard parts; 4- Steel ball standard parts; 5- Instrumentation

Figure 1 Original measurement method

2. Improved calibration method

The improved calibration method is shown in Figure 2. The measurement steps are as follows: (1) Adjust the height of the gauge holder according to the diagram, so that the measuring point H1 of the test gauge rod is close to the bottom position H of the bearing ring groove, and the difference between the two is recorded as δ = ∣H － H1∣  Adjust the position indicated by the tip of instrument 1 to the middle position of the instrument range indicated by the needle as reference point; (2) Select a height standard block with a height size close to the position size of the bearing groove to be measured, compare instrument 2, and use the middle position of the gauge range indicated by the gauge needle as the reference zero position; (3) Adjust the adjustment screw to move the entire measuring meter frame up and down. Observe the movement position of the gauge needle in instrument 1. When the gauge needle reaches a limit position during reciprocating movement, stop rotating the adjustment screw. At this time, the position indicated by the tip of the test gauge rod is the bottom position of the bearing groove; (4) Check the new position indicated by the needle of instrument 2, calculate the number of scales rotated compared to the original position, and record it as δ'。 Due to the fact that two instruments share the same stand, their movement distance is equal, i.e δ = δ'。 Then the position dimension of the bearing channel H=H '± δ =  H '± δ' (When H>H ', take "+"; when H<H', take "-").

1- Measurement platform; 2- Samples to be inspected; 3- Measuring rod; 4- Instrument 1; 5- Instrument guide pillar; 6- Adjust the screw; 7- Meter stand; 8- Instrument 2; 9-Height standard parts

Figure 2 Improved measurement method

This method allows for more accurate verification of the groove position of bearings, as well as measurement of the groove position of certain special structure bearings (which cannot be measured with commonly used instruments).

3 Application effects

To verify the effectiveness of the improved instrument, different specifications of bearing rings were selected as samples, and three measurement methods, namely professional precision instrument (clearance gauge), simple instrument before improvement, and improved instrument, were used to verify the groove position size. The measurement results are shown in Table 1

Table 1 Comparison of Measurement Data

3. Application effect

From the data in the table, it can be seen that the improved measurement method can meet the accuracy requirements of the on-site process and can achieve simple verification of the standard parts at the groove position. In addition, this method has a simple structure and simple operation, and can be directly used as a conventional instrument to measure the groove of bearing parts (especially products with complex groove shapes that are difficult to measure with conventional instruments). Moreover, this instrument is economically applicable and can greatly reduce measurement costs compared to specialized precision instruments.

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