An edge finder tool is a must-have in precision machining, helping machinists accurately locate the edges and center points of a workpiece on a manual milling machine. While not commonly used on CNC machines, edge finders remain essential in traditional, manual machining setups for accuracy and repeatability.
At Travers Tool Company, we offer a wide selection of high-quality edge finders designed to meet the needs of professional machinists and hobbyists alike. With a large variety of edge finders available, this guide covers how to use the .200” mechanical edge finder, which is the most commonly used edge finder, and provides easy-to-follow instructions on how to use it effectively.
If you’re looking for a more in-depth comparison or help choosing the right type, check out our full guide on how to select and use an edge finder.
An edge finder tool consists of a spring-loaded cylinder that spins in a chuck or collet and is a precision tool used in milling operations to precisely locate the edge of a workpiece. The most common type used is the .200” mechanical edge finder with a 1/2" body diameter. Edge finders are also available with a 3/8” body diameter, but the 1/2" body allows more of an offset, giving you an earlier indication of when you’re approaching the workpiece edge, and making it easier to see when the exact edge is reached.
Insert the edge finder into the collet or chuck in your milling machine spindle.
Run the spindle at a moderate speed—typically between 750 and 1500 RPM. Spinning too fast can damage the edge finder, while spinning too slowly may reduce accuracy.
With the spindle running and the tip of the edge finder visibly wobbling off-center, gently move the table to bring the spinning tip toward the edge of your workpiece. Observe closely as the tip starts to center itself, reducing its "wiggle."
As the edge finder contacts the workpiece, the tip will momentarily center and then abruptly "break away" or jump. This breakaway indicates that you are exactly .100” from the true edge of the workpiece (which is half the diameter of the .200” edge finder).
Once the breakaway occurs, set your machine's Digital Readout (DRO) or indicator to zero.
Repeat steps 3 and 4 to ensure your DRO or indicator returns to the zero point set in step 5. If it does, lift the edge finder, move the table another 0.100" in the same direction, and reset your DRO or indicator to zero. This position marks the exact edge of your workpiece relative to the spindle centerline, ensuring accuracy and confidence before beginning the machining operation.
Always clean the workpiece, the edge finder, and the collet it’s going into before use.
Practice a few times to become familiar with the “feel” of the approach and the breakaway.
Travers Tool Co. offers a wide range of precision edge finders and machinist tools that meet the highest standards of quality, or fit the tightest of budgets. Whether you're searching for an edge finder, or any other machinist measurement tools, cutting tools, and much more, Travers Tool is a trusted source known for excellent customer service, competitive prices, and quick delivery.
With over 100 years in the industry, Travers Tool Co. understands the needs of machinists and manufacturers, and our Tech Support people have put in the time and made the chips, working “hands-on” in the metalworking industry for decades. Their online catalog features thousands of high-performance tools, including inspection and layout tools, cutting tools, workholding solutions, and more.