Adjustable parallels are precision tools used in machining to measure, set, and transfer dimensions accurately. They consist of two parallel steel plates that can be adjusted to various widths while maintaining parallelism. These tools are essential for several applications: 1. **Height Measurement**: Adjustable parallels are used to measure the height of workpieces or components. By adjusting the parallel to fit snugly between two surfaces, machinists can determine the exact height or gap. 2. **Setting Up Workpieces**: They help in setting up workpieces on machine tables or fixtures. By ensuring that the workpiece is parallel to the machine table, adjustable parallels contribute to accurate machining operations. 3. **Inspection**: In quality control, adjustable parallels are used to inspect the parallelism and flatness of surfaces. They can be used in conjunction with micrometers or calipers to verify dimensions. 4. **Transferring Measurements**: Adjustable parallels can transfer measurements from one part of a workpiece to another, ensuring consistency and accuracy across multiple components. 5. **Supporting Workpieces**: They can be used as supports or spacers to elevate workpieces to a desired height during machining, ensuring that the workpiece is level and stable. 6. **Tool Setup**: Adjustable parallels assist in setting up cutting tools at precise heights or distances from the workpiece, crucial for operations like milling or drilling. Overall, adjustable parallels are versatile tools that enhance precision and efficiency in machining processes, ensuring that components meet exact specifications and tolerances.

To adjust and secure adjustable parallels, follow these steps: 1. **Select the Parallel**: Choose the appropriate size of adjustable parallel for the gap or slot you need to measure or set. 2. **Loosen the Locking Mechanism**: Most adjustable parallels have a locking screw or nut. Loosen this to allow the parallel to expand or contract freely. 3. **Adjust the Width**: Slide the two halves of the parallel to the desired width. This can be done by hand or by gently tapping with a soft mallet for finer adjustments. Ensure the parallel fits snugly within the gap or slot. 4. **Check the Fit**: Verify that the parallel is evenly expanded and fits tightly without forcing. It should not wobble or tilt. 5. **Secure the Parallel**: Once the desired width is achieved, tighten the locking screw or nut. This will hold the two halves in place, maintaining the set width. 6. **Recheck the Fit**: After securing, recheck the fit to ensure the parallel has not shifted during tightening. Adjust if necessary. 7. **Use in Measurement or Setup**: With the parallel secured, it can now be used for precise measurement or as a setup tool in machining operations. 8. **Store Properly**: After use, clean the parallel to remove any debris or oil, and store it in a protective case to prevent damage. By following these steps, adjustable parallels can be effectively used for accurate measurements and setups in machining and inspection tasks.

Adjustable parallels typically come in sets that include a range of sizes to accommodate various measurement needs. The sizes generally refer to the minimum and maximum width that each parallel can adjust to. A common set might include the following sizes: 1. **3/8 inch to 1/2 inch (9.5 mm to 12.7 mm)** 2. **1/2 inch to 11/16 inch (12.7 mm to 17.5 mm)** 3. **11/16 inch to 15/16 inch (17.5 mm to 23.8 mm)** 4. **15/16 inch to 1-5/16 inch (23.8 mm to 33.3 mm)** 5. **1-5/16 inch to 1-3/4 inch (33.3 mm to 44.5 mm)** 6. **1-3/4 inch to 2-1/4 inch (44.5 mm to 57.2 mm)** These sizes allow for a wide range of adjustments, making them versatile tools for machinists and engineers. The parallels are designed to be used in pairs, and they can be adjusted to fit into slots, gaps, or spaces where precise measurements are required. The ability to adjust them makes them particularly useful for setting up workpieces in milling machines, lathes, or other machining operations where exact spacing is crucial.

To maintain and care for adjustable parallels, follow these steps: 1. **Cleaning**: After each use, clean the parallels with a soft cloth to remove any debris, dust, or metal shavings. Use a brush for hard-to-reach areas. 2. **Lubrication**: Apply a light machine oil to the sliding surfaces to ensure smooth operation and prevent rust. Wipe off any excess oil to avoid attracting dust. 3. **Storage**: Store the parallels in a dry, clean environment. Use a protective case or wrap them in an oil-soaked cloth to prevent exposure to moisture and air. 4. **Inspection**: Regularly inspect the parallels for wear, damage, or corrosion. Check for smooth movement and ensure the locking mechanism functions properly. 5. **Calibration**: Periodically verify the accuracy of the parallels using a micrometer or gauge blocks. Adjust or replace if they are out of tolerance. 6. **Handling**: Handle with care to avoid dropping or knocking them against hard surfaces, which can cause misalignment or damage. 7. **Avoid Over-tightening**: When setting the parallels, avoid over-tightening the locking mechanism to prevent distortion or damage. 8. **Use Proper Tools**: Use appropriate tools for adjustments to avoid damaging the threads or surfaces. 9. **Environmental Control**: Keep the workspace free from excessive humidity and temperature fluctuations to prevent rust and expansion. 10. **Training**: Ensure that all users are trained in the proper use and care of adjustable parallels to maintain their longevity and accuracy. By following these steps, you can ensure that your adjustable parallels remain in good working condition, providing accurate measurements and a long service life.

Adjustable parallels offer several advantages over fixed parallels: 1. **Versatility**: Adjustable parallels can be set to a wide range of sizes, making them suitable for various tasks without needing multiple sets of fixed parallels. This adaptability reduces the need for extensive tool inventories. 2. **Precision**: They allow for precise adjustments to achieve exact measurements, which is crucial in tasks requiring high accuracy. The ability to fine-tune the size ensures better alignment and support in machining operations. 3. **Space Efficiency**: A single set of adjustable parallels can replace multiple sets of fixed parallels, saving space in the workshop. This is particularly beneficial in smaller workspaces where storage is limited. 4. **Cost-Effectiveness**: Although the initial cost of adjustable parallels might be higher, they eliminate the need to purchase numerous fixed parallels, leading to long-term savings. 5. **Ease of Use**: Adjustable parallels are straightforward to set up and adjust, allowing for quick changes between tasks. This efficiency can lead to increased productivity in a workshop setting. 6. **Flexibility in Complex Setups**: They are ideal for complex setups where varying sizes are needed, such as in the case of irregularly shaped workpieces or when working with non-standard dimensions. 7. **Durability**: High-quality adjustable parallels are often made from robust materials, ensuring longevity and consistent performance over time. 8. **Reduced Clutter**: By minimizing the number of tools required, adjustable parallels help maintain an organized and clutter-free workspace, which can enhance workflow and safety. Overall, adjustable parallels provide a practical, efficient, and economical solution for precision measurement and support in machining and inspection tasks.