A combination square is a versatile hand tool used in woodworking, metalworking, and stonemasonry for various measuring and marking tasks. It consists of a ruler and one or more interchangeable heads that can slide along the ruler's length. The most common head is the square head, which allows the tool to be used for checking and marking right angles (90 degrees) and 45-degree angles, making it essential for tasks like squaring up a piece of wood or marking miters. The combination square can also be used as a depth gauge, helping to measure the depth of grooves or holes. By adjusting the position of the square head along the ruler, it can measure and mark specific distances, acting as a ruler or straightedge. The tool often includes a spirit level vial, enabling it to check the level or plumb of surfaces. Additionally, the combination square can be used to find the center of a circular object by aligning the ruler across the diameter and marking the midpoint. Some models include a protractor head for measuring and marking angles other than 90 and 45 degrees, and a center finder head for locating the center of cylindrical objects. Overall, the combination square is prized for its accuracy and multifunctionality, making it an indispensable tool for ensuring precision in layout and measurement tasks across various trades.

A combination square is a versatile tool used for measuring, marking, and checking angles. Here's how to use it: 1. **Measuring and Marking**: - **Length Measurement**: Align the ruler with the edge of the material. Use the scale on the ruler to measure the desired length. - **Marking Lines**: Hold the square firmly against the edge of the material. Use a pencil to draw a straight line along the ruler. 2. **Checking and Drawing Angles**: - **90-Degree Angle**: Place the square's head against the material's edge. Ensure the ruler is perpendicular to the edge to check or draw a right angle. - **45-Degree Angle**: Use the angled side of the square's head to check or draw a 45-degree angle. 3. **Depth and Height Measurement**: - Adjust the ruler to the desired depth or height. Lock it in place using the screw. Use it to measure or mark consistent depths or heights. 4. **Leveling and Plumb**: - Some combination squares have a built-in spirit level. Use it to check if a surface is level or plumb by aligning the bubble between the marked lines. 5. **Transferring Measurements**: - Adjust the ruler to the required measurement. Lock it and use it to transfer the measurement to another piece of material. 6. **Scribing**: - Use the scribe (a pointed tool often included) to mark precise points on the material. 7. **Center Finding**: - For round objects, adjust the square so the ruler bisects the circle. Rotate the square to draw two lines; their intersection is the center. By mastering these functions, a combination square becomes an essential tool for precision in woodworking, metalworking, and other crafts.

A combination square and a double square are both precision tools used in woodworking and metalworking, but they have distinct differences in design and functionality. A combination square consists of a ruler and a movable head that can be adjusted to various angles. The head typically includes a 90-degree square face and a 45-degree miter face, allowing it to be used for marking and measuring right angles and miter cuts. Some combination squares also come with additional features like a spirit level and a scribe for marking. The versatility of the combination square makes it suitable for a wide range of tasks, including checking the flatness of surfaces, measuring depths, and setting angles. In contrast, a double square is simpler in design, consisting of a ruler and a fixed or adjustable head that forms a 90-degree angle with the ruler. Unlike the combination square, the double square does not have a 45-degree miter face or additional features like a spirit level. Its primary function is to check and mark right angles. The double square is often preferred for its compact size and ease of use, making it ideal for tasks that require precision in tight spaces. In summary, the main differences between a combination square and a double square are their design and functionality. The combination square is more versatile with multiple features and angle options, while the double square is more straightforward, focusing on right-angle tasks.

To check for squareness with a combination square, follow these steps: 1. **Preparation**: Ensure the combination square is clean and the blade is securely fixed at a 90-degree angle to the head. 2. **Positioning**: Place the stock (the thicker part of the head) of the combination square against the edge of the workpiece you want to check. 3. **Alignment**: Ensure the blade of the square extends across the surface of the workpiece. The blade should be flat against the surface without any gaps. 4. **Visual Inspection**: Look for any gaps between the blade and the workpiece. If the blade lies flat without gaps, the edge is square. If there are gaps, the edge is not square. 5. **Marking**: If needed, use a pencil to mark along the blade to indicate the square line on the workpiece. 6. **Verification**: For further verification, flip the combination square to the opposite side of the workpiece and repeat the process. Consistent results confirm squareness. 7. **Adjustments**: If the workpiece is not square, adjustments or re-cutting may be necessary to achieve the desired squareness. 8. **Re-check**: After adjustments, re-check the squareness using the same method to ensure accuracy. By following these steps, you can effectively use a combination square to check for squareness in your workpieces.

To adjust a combination square, follow these steps: 1. **Check the Blade**: Ensure the blade is straight and free from damage. If bent or nicked, replace it. 2. **Clean the Components**: Disassemble the square by loosening the locking nut and sliding the blade out. Clean the blade and head with a cloth to remove dirt and debris. 3. **Inspect the Head**: Examine the head for any damage or wear. Ensure the surfaces are smooth and the bubble level is intact. 4. **Reassemble**: Insert the blade back into the head, ensuring it slides smoothly. Align the blade with the desired measurement mark. 5. **Square the Blade**: To ensure the blade is square to the head, place the square on a flat surface with the head against a straight edge. Use a carpenter's square or a known straight edge to check for gaps between the blade and the straight edge. Adjust if necessary. 6. **Adjust the Bubble Level**: If the bubble level is off, adjust it by loosening the screws holding it in place, repositioning it, and tightening the screws. 7. **Tighten the Locking Nut**: Once aligned, tighten the locking nut to secure the blade in place. Ensure it holds the blade firmly without slipping. 8. **Test for Accuracy**: Verify the accuracy by drawing a line along the blade, flipping the square, and drawing another line. The lines should be parallel. If not, repeat the squaring process. 9. **Lubricate**: Apply a light oil to the moving parts to ensure smooth operation and prevent rust. 10. **Store Properly**: Store the combination square in a dry place to maintain its condition. By following these steps, you can ensure your combination square is accurately adjusted and ready for precise measurements.

A combination square consists of several key parts: 1. **Blade (Rule):** The main component, typically a steel ruler, marked with graduations in inches and/or millimeters. It is used for measuring and serves as the base for other attachments. 2. **Square Head:** This is a movable, 90-degree angled head that can slide along the blade. It is used for marking and checking right angles and 45-degree angles. It often includes a spirit level for checking horizontal and vertical alignment and a scribe for marking materials. 3. **Protractor Head:** This component can also slide along the blade and is used to measure and mark angles other than 90 and 45 degrees. It typically has a rotating dial to set and read angles accurately. 4. **Center Finder (Center Head):** This attachment is used to locate the center of cylindrical objects. It has a V-shaped groove that helps in aligning the blade with the center of round workpieces. 5. **Spirit Level:** Integrated into the square head, it is used to ensure surfaces are level or plumb. 6. **Scribe:** A small, pointed tool often stored in the square head, used for marking materials. These components make the combination square a versatile tool for various tasks in woodworking, metalworking, and construction.

To maintain and care for a combination square, follow these steps: 1. **Cleaning**: After each use, wipe the combination square with a clean, dry cloth to remove dust, dirt, and moisture. For stubborn grime, use a mild soap solution and a soft brush, then dry thoroughly. 2. **Lubrication**: Apply a light machine oil or a silicone-based lubricant to the moving parts, such as the blade and the adjusting screw, to ensure smooth operation and prevent rust. 3. **Rust Prevention**: Store the square in a dry place. Consider using a rust inhibitor spray or a silica gel pack in the storage area to absorb moisture. 4. **Calibration**: Regularly check the square for accuracy. Place it against a known straight edge or a machinist's square to ensure the blade is at a true 90-degree angle. Adjust if necessary by loosening the screw, realigning, and retightening. 5. **Storage**: Store the combination square in a protective case or hang it on a tool rack to prevent damage. Avoid placing heavy objects on it or storing it in a cluttered toolbox. 6. **Handle with Care**: Avoid dropping the square or using it as a hammer or pry bar, as this can damage the tool and affect its accuracy. 7. **Blade Care**: Keep the blade free from nicks and scratches. If the blade becomes damaged, it may need to be replaced to maintain accuracy. 8. **Regular Inspection**: Periodically inspect the square for wear and tear, especially the locking mechanism and the blade. Replace any worn or damaged parts promptly. By following these steps, you can ensure your combination square remains accurate and in good working condition for years.