What is Eccentric Turning - How to Do Eccentric Turning on the CNC Lathe

2019/12/16 18:06:07

To solve some special problems in equipment running, eccentric parts and eccentric turning methods are becoming more and more important, and many people searching for how to do eccentric turning on the CNC lathe. Now, dajinprecision.com will introduce what is eccentric turning and CNC turning method of eccentric parts.

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Related Read: Guide to Internal Turning on Lathe

What is Eccentric Turning?

Eccentric turning on a lathe refers to the turning off the center or not on the normal center axis, it can be done on 3 jaw self-centering chuck or 4 jaw chuck in different situations, the 4 jaw chuck with independently moved jaws allows parts to be moved off-center.  The outer circle of the eccentric parts is parallel to the axis of the inner hole or outer circle without overlapping. In mechanical transmission, rotary motion to reciprocating linear motion or reciprocating linear motion to rotary motion is generally accomplished with an eccentric component, like the engine crankshaft in the automobile. 

How to Do Eccentric Turning on the CNC lathe?

When processing CNC parts on a lathe with eccentric turning, the center of the eccentric part must be regulated to coincide with the center of the lathe spindle. 

Common eccentric turning methods for eccentric parts

(1) Eccentric work on a double chuck

This way is to clamp the 3 jaw self-centering chuck on the 4 jaw independent chuck, offset by an eccentric distance, then secure the workpiece to the 3 jaw self-centering chuck. When offsetting the position of the 3 jaw self-centering chuck, the calibration test rod can be clamped in the 3 jaw chuck, and use a dial indicator to ensure the eccentric value position to turn the eccentric parts on a special fixture.

(2) Eccentric work on special fixtures

This method is beneficial for large batches production of eccentric parts, which can shorten the calibration time, improve production efficiency, and ensure processing quality. According to the eccentricity required by the workpiece, turning an eccentric shaft or eccentric sleeve in advance, then mount the workpiece on the eccentric sleeve or eccentric shaft, following with installing them together on the chuck to execute CNC turning. 

(3) Eccentric work on 3 jaw self-centering chuck

This solution is suitable for short eccentric parts. In the 3 jaw self-centering chuck, put a pad with a calculated thickness between any one of the jaws and the contact face of the part. 

An eccentric turning method for an eccentric part with detailed steps:

1. Identify and separate the eccentric and non-eccentric parts of the workpiece.

2. CNC Turn non-eccentric parts and reserve them.

3. Measure the eccentricity of the eccentric part, then calculate the thickness of the pad required in the turning process based on the eccentricity.

4. Clamp the workpiece on the chuck, confirm it is fixed firmly, and measure the radial runout, start turning workpiece, control the error during turning, avoid irrecoverable damage caused by excessive cutting, and stop to test after preliminary turning. After retesting, correct the thickness of the gasket again, and then continue turning until the precision is right.

5. Measure the various indexes of the workpiece (eccentric product), ensure it meets the precision requirements.

Eccentric Hollow Shaft is a typical CNC turning parts product of Dajin Precision, we are specialized in quality custom Eccentric Hollow Shaft manufacturing and rapid CNC machining. 


DAJIN provides excellent quality turning services, precision turned parts, offering professional machining services at competitive price and on timely delivery. With our extensive machining capabilities, we produce the most challenging precision machining parts covering all Industries especially in mass production in automotive industry.