How to choose crankshaft bearings
How to Choose Crankshaft Bearings
Source: China Bearing Network | Time: 2014-07-04
Choosing the right crankshaft bearings is essential for ensuring smooth engine operation and prolonging the life of your machinery. After the crankshaft has been repaired and its grade selected, it's crucial to match it with the appropriate bearing grade. Bearings are typically available in four standard sizes: 0.25mm, 0.5mm, 0.75mm, and 1.0mm. When replacing a bearing, the following key steps should be followed: 1. **Select Based on Journal Size** Choose a bearing that matches the grinding size of the crankshaft. Ensure that the bearing grade corresponds to the specific journal being used. 2. **Check Bearing Length** When installing a new bearing into the housing, both the upper and lower halves should extend slightly above the bearing seat surface by about 0.03–0.05mm. This ensures a tight fit between the bearing and the housing. To check this, install the bearing cap, tighten one bolt to the recommended torque, and use a 0.05mm thick gasket between the other end and the seat. If the bolt can't be tightened properly, the bearing may be too long. If it’s too short, you’ll need to start over. 3. **Ensure Proper Lubrication and Surface Finish** The backside of the bearing should be free of any mottling or imperfections. The surface roughness (Ra) should be around 0.8μm. If the finish is poor, it may affect the bearing’s performance. In such cases, the bearing should be replaced. 4. **Verify Elasticity and Noises** A properly functioning bearing should have the right elasticity to ensure a snug fit within the housing. It should also be free from any dull sounds when tapped. If there’s a dull sound, it may indicate poor contact between the bearing alloy and the base, and the bearing should be replaced. 5. **Check Clearance Between Bearing and Journal** Measuring the clearance between the bearing and the journal is important. Use a micrometer and a cylinder gauge to determine the gap. For connecting rod bearings, apply a thin layer of oil, mount the rod on the journal, and tighten the bolts to the correct torque. You should be able to turn the rod manually by 1–1.5 turns, and feel no play when pulling it along the axis. For main bearings, apply oil to both the journal and bearing surfaces, tighten the bolts, and rotate the crankshaft. A slight resistance is normal, but excessive friction should be addressed. 6. **Ensure Coaxial Alignment of the Seat Holes** The centerline of each main bearing must be aligned. Check the alignment by removing the bearing cover and lifting the crankshaft. All contact areas should be evenly distributed. If not, minor repairs may be needed. However, if the misalignment is significant or some bearings don’t make contact, it may be necessary to recheck the coaxiality of the housing bore or select a different bearing. --- **Related Bearing Knowledge** - How to Anneal Thrust (Positioning) Bearings for High Carbon Chromium Bearing Steel - Discussion on the Detection Method for INA Plastic Bearing Noise - Analysis of Methods for Dealing with Overheating Imported Bearings This article was originally published at http://www.chinabearing.net. Please cite the source as China Bearing Network – http://www.chinabearing.net. Previous: Application Example of Long-Life Rolling Bearing Next: Layout Characteristics and Effect of Thrust Bearing
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