Calipers are essential tools for any machinist or engineer. They are used to measure the outside diameter (OD), inside diameter (ID), and depth of a wide variety of objects. Calipers come in a variety of sizes and shapes, but all of them work on the same basic principle: two jaws that are moved together or apart to measure the distance between two points. The jaws are typically made of hardened steel, and they are often equipped with a dial or digital readout to provide precise measurements.
Calipers can be used to measure a wide range of objects, including shafts, rods, tubes, and holes. They are also commonly used to measure the thickness of materials, such as sheet metal or plastic. To use calipers to measure the OD of an object, simply close the jaws around the object and read the measurement on the dial or digital readout. To measure the ID of an object, insert the tips of the jaws into the hole and then close the jaws until they touch the sides of the hole. To measure the depth of a hole, insert the tips of the jaws into the hole and then close the jaws until they reach the bottom of the hole.
Calipers are relatively easy to use, but there are a few things to keep in mind when using them. First, it is important to make sure that the jaws are clean and free of any debris. Second, it is important to apply even pressure to the jaws when closing them. Finally, it is important to read the measurement carefully and to make sure that it is accurate. Calipers are a versatile and essential tool for any machinist or engineer. With proper care and use, they can provide accurate and reliable measurements for many years to come.
Essential Tools and Equipment
Dial Caliper
A dial caliper is the most versatile type of caliper for measuring lengths, widths, and depths. It consists of a main scale with a sliding jaw that has a vernier scale. The vernier scale allows for precise measurements to the nearest 0.01 millimeter (0.005 inches).
Mitutoyo Dial Caliper
Mitutoyo is a leading manufacturer of precision measuring tools and their dial calipers are considered the industry standard. They offer a wide range of models to suit different applications, with features such as digital displays, built-in depth gauges, and interchangeable anvils.
Here is a table summarizing the key features of the Mitutoyo CD-6″ CX dial caliper:
| Feature | Specification |
|---|---|
| Measuring range | 0-6 inches (0-150mm) |
| Accuracy | ±0.001 inches (±0.02mm) |
| Resolution | 0.0005 inches (0.01mm) |
| LCD display | Yes |
| Depth gauge | Built-in |
| Interchangeable anvils | Yes |
Selecting the Right Caliper
Choosing the right caliper for your specific application is crucial for accurate measurements. Consider these factors when selecting a caliper:
Type of Caliper
Dial caliper: Features a circular dial that indicates measurements. Ideal for quick and approximate readings.
Vernier caliper: Uses a sliding scale to provide precise measurements. Preferred for applications requiring high accuracy.
Digital caliper: Displays measurements electronically on a digital readout. Offers convenience and high accuracy.
Range and Resolution
Determine the measurement range you need. Consider the maximum and minimum measurements you will be taking. Resolution refers to the smallest increment that the caliper can measure. A higher resolution provides more precise measurements.
Accuracy
Accuracy is typically expressed as a percentage of the full-scale range. A higher accuracy rating indicates a more reliable caliper. For critical measurements, a caliper with high accuracy is essential.
Jaw Type
Outside jaws are used to measure external dimensions. Inside jaws are used to measure internal dimensions. Some calipers feature interchangeable jaws for added versatility.
Material
Calipers are typically made of steel or plastic. Steel calipers are more durable but can rust. Plastic calipers are lightweight and affordable but may be less durable.
Consider the following table for a summary of the key factors:
| Type | Range | Resolution | Accuracy |
|---|---|---|---|
| Dial | <20 inches | 0.001 inches | +/-0.002 inches |
| Vernier | <24 inches | 0.001 inches | +/-0.001 inches |
| Digital | <48 inches | 0.0005 inches | +/-0.0005 inches |
Measuring Inside Diameters
To measure inside diameters, adjust the calipers so that the outside jaws are just touching. Zero the caliper. Insert the outside jaws into the hole to be measured. The reading on the caliper will be the inside diameter of the hole.
Special Considerations for Measuring Inside Diameters
There are a few special considerations to keep in mind when measuring inside diameters:
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The jaws of the caliper must be parallel to the surface of the hole. If the jaws are not parallel, the reading will be inaccurate.
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The caliper must be zeroed before taking a measurement. If the caliper is not zeroed, the reading will be inaccurate.
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The hole must be large enough for the caliper jaws to fit inside. If the hole is too small, the caliper will not be able to take a measurement.
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The caliper must be held steady while taking a measurement. If the caliper is not held steady, the reading will be inaccurate.
| Measurement | Caliper Reading |
|---|---|
| Inside diameter of a hole | Distance between the outside jaws |
Measuring Outside Diameters
To measure the outside diameter of a cylindrical object using a caliper, follow these steps:
- Ensure that the caliper is set to the “outside” measuring mode.
- Open the caliper’s jaws wide enough to fit the object.
- Carefully align the outside edges of the jaws with the object’s surface.
- Tighten the knurled thumb screw to secure the object in place.
- Read the measurement from the scale on the caliper’s beam.
Additional Tips for Measuring Outside Diameters
For more accurate measurements, follow these tips:
| Tip | Description |
|---|---|
| Clean the caliper jaws | Remove any dirt or debris that could affect the accuracy of the measurement. |
| Use a magnifying glass | For very small measurements, a magnifying glass can help you read the scale more precisely. |
| Take multiple measurements | Measure the object from different angles to ensure consistency. |
| Calibrate the caliper regularly | Over time, calipers can become misaligned. Calibrating them ensures accurate measurements. |
Measuring Depth
Measuring the depth of a hole or slot with a caliper requires a slightly different approach than measuring the thickness of an object. Here are the steps involved:
1. Position the Caliper Jaws
Position the lower jaw of the caliper against the bottom of the hole or slot. Align the upper jaw parallel to the lower jaw, ensuring it’s just touching the opposite surface of the cavity.
2. Stabilize the Caliper
To ensure accurate measurements, stabilize the caliper by holding it firmly against the workpiece. Use your thumb to apply gentle pressure on the thumb screw to secure the jaws in place.
3. Lock the Jaws
Once the caliper jaws are properly positioned, lock them in place using the locking screw. This will prevent the jaws from moving and ensure the reading remains constant.
4. Read the Measurement
Read the measurement on the caliper scale. The depth of the hole or slot is the vertical distance between the two jaws. It’s important to note that the measurement may vary slightly depending on the type of caliper used.
5. Types of Depth Calipers
There are different types of depth calipers designed for specific measuring applications. Here are a few common types:
| Type | Description |
|---|---|
| Inside Calipers | Used to measure the inside diameter of holes or the depth of a cavity. |
| Outside Calipers | Used to measure the outside diameter of shafts or the width of a slot. |
| Offset Calipers | Designed with offset jaws to reach into recessed or hard-to-reach areas. |
| Digital Depth Calipers | Provide precise measurements with digital displays and can measure depth, inside diameter, and outside diameter. |
Reading Caliper Measurements
When reading caliper measurements, it is important to pay attention to the following details:
1. Zero Setting
Before taking any measurements, make sure that the calipers are properly zeroed. This involves closing the jaws of the calipers and adjusting the zero point on the dial or digital readout to zero.
2. Inside and Outside Measurements
Calipers can be used to measure both inside and outside dimensions. For inside measurements, place the jaws inside the object and read the measurement on the dial or digital readout. For outside measurements, place the jaws outside the object and read the measurement on the dial or digital readout.
3. Reading the Dial
Dial calipers have a dial that indicates the measurement in thousandths of an inch (0.001 inches). To read the dial, start by locating the zero point. Then, count the number of major divisions (each representing 0.100 inches) and the number of minor divisions (each representing 0.001 inches). Add these values together to get the total measurement.
4. Reading the Digital Readout
Digital calipers have a digital display that indicates the measurement in inches or millimeters. To read the digital readout, simply read the number that is displayed.
5. Accuracy
The accuracy of caliper measurements depends on the quality of the calipers and the skill of the user. High-quality calipers can measure with an accuracy of ±0.001 inches (0.025 mm). However, it is important to note that even high-quality calipers can be inaccurate if they are not used properly.
6. Vernier Caliper Measurement
Vernier calipers are similar to dial calipers, but they have a movable scale called a vernier scale. The vernier scale allows for more precise measurements than dial calipers. To read a vernier caliper, first read the measurement on the main scale. Then, locate the line on the vernier scale that lines up exactly with a line on the main scale. The number on the vernier scale at this point represents the thousandths of an inch (0.001 inches) part of the measurement.
| Measurement | Reading |
|---|---|
| Main scale | 0.500 inches |
| Vernier scale | 0.015 inches |
| Total measurement | 0.515 inches |
Calibrating Your Caliper
Calibrating your caliper is an essential step to ensure accurate measurements. Here’s how to do it effectively:
1. Gather Essential Tools
You will need a standard block or a precision gauge of a known size, a screwdriver (if applicable), and a clean cloth.
2. Prepare the Caliper
Wipe the caliper’s measuring surfaces with a clean cloth to remove any dirt or debris.
3. Zero the Caliper
Close the measuring jaws together and gently adjust the zero knob until the jaws touch without applying any pressure. This sets the caliper to zero.
4. Check the Calibration
Insert the standard block or gauge between the measuring jaws and take a measurement. The measurement should match the known size of the block.
5. Adjust the Calibration If Needed
If the measurement does not match the known size, use the screwdriver to adjust the zero knob. Move the knob slightly until the measurement matches the standard block’s size.
6. Verify the Calibration
Remove the standard block and close the jaws again. The caliper should still read zero. If it does not, repeat steps 3-5 until the calibration is correct.
7. Compensate for Measuring Forces
When measuring soft materials, the measuring force can affect the accuracy of the measurements. To compensate for this:
| Material Type | Measuring Force |
|---|---|
| Soft materials (e.g., rubber, leather) | Low force (e.g., 1-2 pounds) |
| Hard materials (e.g., metal, plastic) | Higher force (e.g., 5-10 pounds) |
Troubleshooting Common Problems
8. Stuck Calipers
Sticky calipers sometimes release and may start working normally with the steps from previous troubleshooting methods. Calipers may also become stuck when they are not engaged frequently. However, if the calipers are rusted, there are further steps to take. To do this, you will need to remove the caliper from the brake rotor and disassemble it. If the calipers are not rusted shut, apply penetrating oil to the pins and pistons. Use a wire brush to remove any rust from the caliper. After the rust is removed, reassemble the caliper and test it. If the caliper is still stuck, it will need to be replaced.
Below is a chart that outlines the different types of caliper sticking problems and their solutions:
| Problem | Solution |
|---|---|
| Sticking caliper piston | Clean and lubricate the piston and bore. |
| Sticking caliper slide pins | Clean and lubricate the slide pins. |
| Rusted caliper bolts | Remove the bolts and replace them with new ones. |
Advanced Caliper Techniques
Measuring Large Diameters
Use a large-diameter caliper or a micrometer. To use a micrometer, place the anvil against one edge of the object and the spindle against the other edge. Read the measurement on the scale.
Measuring Small Diameters
Use a small-diameter caliper or a dial indicator. To use a dial indicator, attach it to the caliper and place the contact point on the object. Read the measurement on the dial.
Measuring Thickness
Place the object between the jaws of the caliper and close the jaws until they touch the object. Read the measurement on the scale.
Measuring Depth
Insert a depth probe into the hole or slot and close the jaws until the probe touches the bottom. Read the measurement on the scale.
Measuring Angles
Use a protractor or an angle finder. To use a protractor, align the baseline of the protractor with one leg of the angle and read the measurement on the scale. To use an angle finder, place the angle finder on the angle and read the measurement on the display.
Measuring Radii
Use a radius gauge. To use a radius gauge, place the gauge on the radius and read the measurement on the scale.
Measuring Spheres
Use a sphere micrometer. To use a sphere micrometer, place the sphere between the anvil and the spindle and close the jaws until they touch the sphere. Read the measurement on the scale.
Measuring Irregular Surfaces
Use a surface gauge. To use a surface gauge, attach a scriber to the gauge and move the gauge over the surface. The scriber will create a line on the surface that can be measured with a caliper.
Using a Calliper Tool with a Digital Display
Calipers with digital displays offer several advantages over traditional calipers, including:
- Increased accuracy and precision
- Easier reading
- Data storage and retrieval capabilities
To use a calliper with a digital display, simply follow the manufacturer’s instructions.
Safety Precautions
1. Wear Personal Protective Equipment (PPE)
Wear safety glasses to protect your eyes from flying debris or metal shavings. Use gloves to prevent cuts and abrasions from handling sharp edges. Wear earplugs or earmuffs to minimize noise levels.
2. Inspect the Caliper
Before using the caliper, check for any damage or loose parts. Ensure the jaws are clean and well-lubricated to prevent sticking.
3. Secure the Workpiece
Hold or clamp the workpiece firmly in place to prevent it from moving or slipping during measurement.
4. Use a Steady Hand
Hold the caliper firmly and move it gently along the workpiece to ensure an accurate reading.
5. Avoid Over-Tightening
Do not over-tighten the jaws of the caliper, as this can damage the workpiece or the caliper itself.
6. Keep the Caliper Clean
Clean the caliper regularly to remove any dirt or debris that may interfere with accurate measurements.
7. Store the Caliper Properly
When not in use, store the caliper in a dry, dust-free environment to prevent corrosion.
8. Use the Correct Measuring Range
Select a caliper with the appropriate measuring range for the workpiece being measured. Using a caliper with an insufficient range can lead to inaccurate readings.
9. Read the Dial or Digital Display Carefully
Ensure you accurately interpret the readings from the dial or digital display on the caliper.
10. Vernier Caliper Specific Precautions
When using a vernier caliper, pay special attention to the following:
Precaution Reason Align the zero marks To ensure accurate starting point for measurements Read the main scale first To determine the whole number measurement Estimate the tenth decimal Using the vernier scale to interpolate the fractional value Avoid parallax error Look perpendicularly at the scales to prevent error caused by viewing angle How To Caliper
Calipers are measuring instruments used to determine the distance between two points, the thickness of an object, or the depth of a hole. They are commonly used in engineering, manufacturing, woodworking, and other industries. There are different types of calipers, including vernier calipers, dial calipers, and digital calipers. Vernier calipers are the most common type and consist of a main scale and a vernier scale that slides along the main scale. Dial calipers have a dial that displays the measurement, while digital calipers display the measurement on a digital display.
To use a caliper, first select the appropriate caliper for the measurement you need to make. Then, position the caliper on the object to be measured and adjust the jaws of the caliper until they touch the object. Finally, read the measurement from the scale or display.
People Also Ask About How To Caliper
How to measure the inside diameter of a hole?
To measure the inside diameter of a hole, use a pair of inside calipers. Insert the tips of the calipers into the hole and adjust the jaws until they touch the sides of the hole. Then, read the measurement from the scale or display.
### How to measure the outside diameter of a shaft?
To measure the outside diameter of a shaft, use a pair of outside calipers. Place the jaws of the calipers around the shaft and adjust the jaws until they touch the sides of the shaft. Then, read the measurement from the scale or display.
### How to measure the thickness of a sheet of material?
To measure the thickness of a sheet of material, use a pair of thickness calipers. Place the tips of the calipers on the edge of the material and adjust the jaws until they touch the sides of the material. Then, read the measurement from the scale or display.
