Measuring the internal diameter of a cylinder, bushing, or tube requires a tool that can access the measurement location and provide results consistent with tolerance coordinates. This article explains how to use a comparative bore gauge, how to read the reversal point, and what to check when selecting a tool suitable for the job.
What is a Bore Gauge?
A bore gauge is a tool used to measure the internal diameter of a hole, such as a cylinder, tube, or bushing. This article focuses on two-point contact bore gauges that read the difference from a reference size, using a dial or digital display depending on the model.
Principle of Operation of Bore Gauge
The two-point contact bore gauge uses contact heads on opposite sides of the hole wall. When the distance between the contact heads changes, the measuring rod sends the movement to the display. Models with supports make it easier to align the measuring head in the hole. The measurement principle is a comparison with a known size.
Select Contact Heads and Set Reference
Select contact heads and spacers according to the measurement range of the model, and set them using a reference device with a known size, such as a setting ring or an external micrometer with a set that the manual supports. Gently move the bore gauge in the reference device until the display reaches the reversal point. Then set zero or the reference value according to the manual.
Find the Reversal Point in the Workpiece Hole
Place the measuring head at the depth according to the inspection plan of the workpiece, and gently move the measuring rod so that it passes the position where the display changes direction. Use the reversal point as the reading position, and set the reference with the workpiece in the same orientation as recommended by the manual for that model. Check the display direction before interpreting whether the hole is larger or smaller than the reference value.
Convert the Read Value Compared to the Reference Size
For example, if the reference is set at 50.00 mm and the reading according to the manual shows that the hole is smaller than the reference by 0.02 mm, the diameter at that position is 49.98 mm. If you need to check the difference along the depth or ovality, measure repeatedly at multiple levels and directions according to the inspection plan.
How many types of Bore Gauge are there?
Consider both the display method and the probe tip characteristics, as they affect the setup method, access to the hole, and reading results.
Categorized by Display System
The analog type reads values from a scale, while the digital type displays values as numbers. Functions such as minimum value recording or data export are available only on supported models. Check the resolution and display method from the instrument's specifications.
Categorized by Probe Tip and Contact Points
The two-point bore gauge uses opposing probe tips and is suitable for measuring sizes in a specified direction. A three-point micrometer is another option when the hole shape and depth are suitable for the probe tip. Models for small or tapered holes have different limitations regarding range and depth.
Bore Gauge Maintenance
Proper maintenance of the bore gauge is the most important factor in maintaining accuracy. Industry-standard preventive practices to avoid internal mechanism damage are as follows:
Proper Cleaning
Clean the probe tip, reference device, and hole surface before measurement. After use, clean according to the manual, for example, use a soft dry cloth for Starrett 3089 and avoid compressed air blowing or submerging the tool in liquid.
Checking the Mechanism Before Use
Ensure that the probe tip moves smoothly, the locking points are in position, and the display responds consistently. Grip the handle according to the manual to limit the effect of hand heat. Measure when the workpiece is stationary and in a safe condition.
Proper Storage and Rust Prevention
Store the tool in a box in a dry place, away from shocks and temperature changes. If stored for a long time, follow the manual for that model, for example, Starrett 3089 should release the initial pressure of the display before long-term storage.
Instrument Calibration
Zeroing with a reference device prepares the gauge for measurement, while calibration checks the performance of the instrument and reference device. Determine the calibration cycle based on job coordinates, frequency, usage conditions, calibration history, and customer or quality system requirements.
Application of Bore Gauge in Industry
Bore Gauge is an important tool for controlling the quality of parts. SCMA Co., Ltd. (SCMA), as a leader in measuring and testing tools, sensors, and automation systems, is ready to support industrial equipment that meets every application need.
Measuring Internal Bores and Cylinders
Measure diameters at multiple depths to compare roundness, and measure at multiple directions on the same cross-section to screen for ovality. If you need to confirm roundness according to specific criteria, use the method and shape measuring tools as specified by the job requirements.
High-Precision Quality Control
The bore gauge allows the quality control department to inspect and record the hole size at a specified location before deciding whether the part passes or not. Compare the value with the tolerance coordinates and inspection method according to the job specification.
Use with Standard Reference Equipment
For comparative bore gauges, select a setting device with a known size and suitable for the measurement range, such as a setting ring or a set with an external micrometer according to the manual. Recheck the reference value according to the inspection plan, especially after changing the contact tip or when there is a suspicion of deviation.
Advantages of Bore Gauge
SCMA's internal bore gauges and diameter measuring devices stand out in terms of accuracy. These devices are designed to meet the demands of heavy-duty use in the industrial sector specifically.
Directly Check Deviations from Reference Size
The values displayed by the comparative bore gauge show how much the hole size differs from the reference value. The quality of the result depends on the instrument specification, reference equipment, temperature, and the measuring operator's alignment method.
Select the Measuring Head Set Suitable for the Part
Models that allow replacement of the contact tip and setting rings support multiple hole size ranges. Check the stem depth and the type of hole (blind or through) before selecting, and use them according to the temperature conditions and maintenance instructions specified by the manufacturer.
Consultation and Specification Matching Services from SCMA
SCMA has a team of expert engineers ready to advise on selecting the Bore Size that matches the actual work surface characteristics. We provide equipment specification matching services and quickly resolve issues related to replacement parts, so that your production line can continue smoothly.
How to Choose a Bore Gauge
Purchasing and inspecting industrial measuring instruments through SCMA will help you receive accurate advice to get a Bore Gauge that best matches your work requirements.
Measurement range and depth: Select contact tips and stems that cover the hole size and access positions required.
Accuracy and performance: Check the specification of accuracy, deviation, and repeatability in conjunction with the tolerance of the workpiece.
Two-point contact tip: Suitable for comparative measurement in a specified direction. Practice reading reverse direction points and check the display direction according to the manual.
Three-point contact tip: Consider three-point micrometers when suitable for the shape and depth of the hole, and follow the setup method of that model.
Reference equipment: Prepare setting rings or sets that support the measurement range and check the calibration status according to the quality system of the site.
Why Choose Industrial Measuring Instruments from SCMA?
SCMA is not just a distributor, but we are a technical partner specialized in automation systems. We are ready to deliver solutions that meet the needs of the Thai industry.
High-quality measuring instruments hub: We select only equipment that meets international standards, is durable, and provides accurate measurement values.
Expert engineering team: Provide technical advice to help you choose the right specification Bore Gauge and measuring instruments for your production process.
Comprehensive after-sales service: Supports everything from calibration work, maintenance, to project design.
Easy access, fast service: Has branches covering major industrial estates, ready to solve your problems promptly.
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Summary
Bore Gauge or Bore Gauge is a high-precision measuring instrument indispensable for quality control of holes in industrial parts. Choosing the right type and maintaining it properly will help maintain accuracy and extend its service life. If your factory is looking for high-standard measuring instruments and reliable calibration services, the engineering team from SCMA is ready to be your comprehensive consulting partner.
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If you want to buy a Bore Gauge, you can buy it from SCMA today!
Investing in non-standard measuring instruments has a negative impact on product quality and causes huge hidden costs. High-quality Bore Gauge helps you measure accurately and effectively reduce waste in the production line. We are ready to deliver industrial measuring instruments and automation systems in a comprehensive manner, along with technical consulting services to upgrade your factory.
Frequently Asked Questions
What does a Bore Gauge measure?
It measures the internal diameter, such as pipes, bushings, or cylinder bores. Multi-directional and multi-level measurements help compare size differences according to position.
What is the difference between a 2-point and 3-point Bore Gauge?
A 2-point Bore Gauge uses opposing contact points and finds the reversal point when used in comparison mode, while a 3-point micrometer uses three contact positions to help align. Choose according to the shape and inspection criteria of the part.
Why should you set the zero before using a Bore Gauge?
Reference setting allows interpretation of the difference values displayed by the instrument. Use equipment with known dimensions, such as setting rings, and follow the method of the model in use.
How often should a Bore Gauge be calibrated?
Determine the cycle according to the required accuracy of the job, relevant requirements, instrument stability, and usage conditions. If there are past calibration results, use them to review the cycle according to NIST guidelines.
Does SCMA offer after-sales service for measuring instruments?
SCMA offers comprehensive after-sales service, covering calibration, maintenance, and technical consulting by expert engineers.
Reference Documents
Starrett — 3089 Dial Bore Gage Manual
