1. The plane oil seal products check the appearance quality. The surface of the skeleton oil seal must be smooth and free of defects such as burrs, cracks, bubbles, missing corners and impurities embedded; the edge of the oil lip is sharp, without gaps, burrs and unevenness. The contact width between the lip and the shaft is generally 0.13-0.5mm, and the optimum width is 0.25mm; the bonding between the rubber and the reinforcement ring should be tight and not loose, the reinforcement ring should not be offset, and the inner and outer surfaces should not be exposed. Iron; the embossed characters on the oil seal plane are marked with "shaft diameter × outer diameter × height", the manufacturer's name and trademark, and the handwriting should be clear.

　　2. Use a vernier caliper to measure the size of the oil seal. It is best to use a standard plug gauge to measure the inner diameter to check whether the tightness of the combined gasket is appropriate. If the inner diameter of the oil seal is greater than 30-90mm, the tolerance is -1.0-+0.7mm; if the height is greater than 4mm, the tolerance is -0.3-+0.40mm. According to the requirements of the manufacturer of The plane oil seal products, the oil seal cutting edge should have an appropriate amount of interference with the matching journal. If it is too large, it will affect the service life of the oil seal. If it is too small, the sealing performance will deteriorate.

　　3. The plane oil seal products When the machine is working, the radial force of the oil seal lip on the shaft causes an oil film with a thickness of about 2.5mm between the interfaces, which is the essence of the sealing effect of the skeleton oil seal.