How to measure and adjust the bearing clearances in the large and small ends of a compressor

After the connecting rod is installed, it is measured with an inner-diameter micrometer; the crank pin and crosshead pin are measured with an outer-diameter micrometer. If the clearance is too small, the bearing shells need to be scraped; if the clearance is too large, the bearing shells must be replaced or steel plates inserted behind them

What size is the machine? Taking 4M65 as an example, the spindle diameter is 340 mm, and the clearance of the large-end bearing shell is 0.25 mm ； The size of the small-headed tile is 0.19–0.24 mm. I remember there being a formula for the clearance standard; it seems to be around 0.75–1.2 percent of the shaft diameter

It’s best to follow the manufacturer’s instructions; use the amount specified in those instructions, unless there are obvious errors in them! This requires consulting the manufacturer.

1. Measure the gap with a feeler gauge. For fine adjustments of the gap, scraping the wiper is usually done. If it gets too large, it’s basically beyond use. 2. The compressor user manual is the standard! !

Place a wire between the bearing shell and the shaft; after tightening the screws that hold the bearing shell in place, remove them again and measure the thickness of the wire – this thickness represents the clearance of the bearing shell. This is a makeshift solution.

The most convenient option is a outside diameter micrometer combined with an inside diameter dial indicator.

Could you please tell me the more detailed steps on how to do it?

Use an outer diameter micrometer to determine the degree of locking of the crankshaft. Then, place an inner diameter dial indicator inside the outer diameter micrometer and zero it. Next, use the magnifying part of the dial indicator to observe the movement of the crankshaft bearings back and forth; the range of this movement should not exceed 15 degrees. The highest reading obtained represents the clearance between them

Use a feeler gauge to measure the axial clearance of the crankshaft positioning bearing (on the side near the motor); the design value is 0.22~0.45 mm. Use an inner diameter dial indicator to measure the clearance between the large-end bearings and the small-end bearings; the clearance should be controlled at 0.15 MM (with a standard range of 0.12–0.18 mm). Check whether there is any looseness or defects in the fit between the crosshead bushing and the crosshead. Visual inspection: The connecting rods and rod bolts show no defects such as cracks; if necessary, inspections can be carried out using coloring, magnetic particle testing, or ultrasonic testing. The end face of the connecting rod bolt and the end face of the connecting rod bolt hole should be lapped to ensure even contact, with a contact area of not less than 80%. The connecting rod bolt elongates by 0.88±0.05 mm during installation.