Plastigage is a thin, malleable wire used to measure bearing clearances. To use it, select the appropriate thickness, apply it to the bearing journal, and torque the bolts. Remove the Plastigage after torquing and measure its crushed width. Match the width to a color chart to determine the exact bearing clearance value. Ensure accuracy by using clean surfaces, applying even pressure, and allowing for plastigage expansion.
Unveiling the Secrets of Bearing Clearance Measurement: A Guide to Plastigage
In the realm of mechanics, precise bearing clearance ensures the smooth operation of rotating machinery. Measuring this clearance accurately is crucial for optimizing performance and preventing costly failures. Enter Plastigage, a revolutionary tool that makes this task a breeze.
Plastigage is a specially formulated polymeric strip that, when inserted between a bearing and its journal, provides a highly accurate measurement of the clearance upon assembly. By crushing and flattening under the pressure of the tightened bolts, Plastigage reveals the exact gap between the two surfaces.
Essential Concepts in Plastigage Measurement
A. Bearing Clearance Measurement: The Key to Optimal Performance
Proper bearing clearance is critical for smooth operation and extended component life. Measuring this gap between the bearing and its journal is essential to ensure optimal performance.
Plastigage acts as a versatile tool in this measurement process. It consists of a thin strip of precisive plastic that flattens under force. By placing Plastigage on the bearing journal before torquing, you can accurately determine the clearance as the Plastigage flattens during assembly.
B. Plastigage Application: Ensuring Accuracy
Selecting the appropriate Plastigage thickness is crucial. The correct thickness will ensure sufficient material to measure the clearance while avoiding excessive flattening.
Proper application involves placing the Plastigage strip along the center of the bearing journal. Avoid overlapping or gaps, as this can compromise the accuracy of the measurement.
C. Plastigage Clearance Measurement: Interpreting the Results
After torquing the bolts, carefully remove the Plastigage from the bearing. The _crushed width of the Plastigage corresponds to the bearing clearance._
Measure the crushed width using a caliper or ruler. _Compare the measurement to a color chart provided by the Plastigage manufacturer to determine the exact bearing clearance._
D. Bearing Clearance Gauge: An Alternative for Precision
While Plastigage is a widely used method, bearing _clearance gauges offer an alternative for more precise measurements. These gauges directly measure the clearance, providing accurate readings with minimal uncertainty._
E. Plastigage Reading: Unraveling the Color Code
Plastigage strips are typically color-coded to simplify and enhance accuracy. Match the crushed width of the Plastigage to the corresponding color on the _color chart. This will provide the exact bearing clearance value in a convenient and straightforward manner._
Practical Considerations for Plastigage Accuracy and Limitations
Plastigage Accuracy: Ensuring Precise Measurements
Understanding the factors that can affect Plastigage accuracy is crucial for reliable bearing clearance measurements. Ambient temperature plays a significant role, as Plastigage is temperature-sensitive. Measuring in controlled temperature conditions minimizes errors. Additionally, proper installation is essential. Ensure the bearing is correctly positioned and torqued to the specified value before applying Plastigage.
Plastigage Limitations: Beyond Its Capabilities
While Plastigage offers a straightforward method for clearance measurement, it has certain limitations. For extremely tight or loose clearances, Plastigage might not provide the desired level of accuracy. In such cases, dial indicators or micrometers provide more precise measurements. Moreover, Plastigage is not suitable for measuring clearances in oval or tapered bearings. For these applications, alternative methods like bearing clearance gauges are more appropriate.
Alternative Measurement Methods: Expanding Your Toolkit
When Plastigage falls short, other measurement techniques can come to the rescue. Dial indicators directly measure the gap between the bearing and journal, providing highly accurate readings. Micrometers measure the bearing’s outer diameter before and after assembly, indicating the clearance by subtracting the values. For oval or tapered bearings, bearing clearance gauges are specifically designed to conform to the bearing’s shape, providing accurate measurements.
