A center head is an essential attachment for a combination square, primarily used to accurately find and mark the center of round, cylindrical, or square stock. This tool is invaluable in woodworking, metalworking, and machining for precise layout, drilling, and turning operations.
Understanding the Center Head
The center head typically features a V-shaped body that cradles the workpiece, ensuring the attached rule (blade) passes directly through the object's center. When paired with the rule, it allows for quick and precise identification of the central point on the end of a shaft, dowel, or plate.
Finding the Center of Round or Cylindrical Stock
The most common application for a center head is locating the center of circular or cylindrical workpieces. This process involves scribing intersecting lines to pinpoint the exact middle.
Step-by-Step Guide:
- Assemble the Tool: Attach the center head to the rule (blade) of your combination square. Ensure it is securely fastened.
- Position the Center Head: Firmly place the V-shaped arms of the center head against the circumference of the round or cylindrical stock. The rule should extend across the end face of the object you wish to center.
- Scribe the First Mark: Using a sharp pencil or a scribe, draw a short, distinct line along the edge of the rule across the diameter of the end face. This mark represents the first diameter line.
- Reposition and Scribe Again: Move the tool to a new point on the circumference of the object. Rotate the object approximately 90 degrees relative to the tool, or simply reposition the center head to a different section of the circumference, ensuring the V-arms are still snugly against the edge.
- Scribe the Second Mark: Draw another short mark across the diameter, similar to the first.
- Identify the True Center: The point where the lines cross is the true Center of the round or cylindrical stock. For increased accuracy, you can repeat steps 4 and 5 one or two more times, scribing additional lines. All lines should intersect at the exact same central point. This technique is the same for cylindrical objects of any length.
Key Tips for Accuracy:
- Snug Fit: Always ensure the V-groove of the center head is held firmly against the circumference of the workpiece.
- Sharp Scribe: A sharp pencil or metal scribe creates finer, more accurate lines, making the intersection point clearer.
- Multiple Lines: While two intersecting lines are sufficient, drawing three or four lines by repositioning the tool further validates the center point.
Using for Square or Rectangular Stock (as Diagonals)
While specifically designed for round stock, a combination square's rule can also assist in finding the center of square or rectangular stock. Although not directly using the "center head" attachment for this, it's a related layout task where the rule is invaluable.
- Scribe Diagonals: To find the center of a square or rectangular piece, simply use the rule of your combination square (or any straight edge) to draw two diagonal lines from opposite corners. The point where these diagonals intersect is the center.
Benefits of Using a Center Head
Using a center head offers several advantages for various projects:
- Precision: Ensures highly accurate centering, crucial for drilling pilot holes, turning on a lathe, or precise marking.
- Efficiency: Saves time compared to more complex manual layout methods.
- Versatility: Usable on a wide range of diameters for both round and cylindrical materials.
- Reduced Error: Minimizes human error in locating centers, leading to better project outcomes.
| Application | Benefit |
|---|---|
| Drilling | Ensures holes are perfectly centered |
| Lathe Work | Essential for mounting stock accurately |
| Layout & Marking | Foundation for precise design transfer |
| Joinery | Aids in aligning components for assembly |
Conclusion
The center head, as part of a combination square, is an indispensable tool for anyone needing to precisely locate the center of round, cylindrical, or even square stock. Its straightforward application ensures accuracy, saving time and improving the quality of your work in various crafts and trades.
