Introduction

An edge finder is an essential tool 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 indispensable in traditional machining setups for layout accuracy and setup repeatability.

At Travers Tool Company, we offer a wide selection of high-quality edge finders designed to meet the needs of both professional machinists and hobbyists. This guide explains how to choose the right edge finder and provides step-by-step instructions on for using it effectively.

Types of Edge Finders

Selecting the right edge finder for your milling setup depends on your specific application. Travers Tool carries various types to suit different precision tasks:

1. Mechanical Edge Finders

• The most widely used and traditional type of edge finder

• Features a spring-loaded body with a cylindrical or pointed tip

• Turns in the spindle and visually offsets (or “jumps”) upon contact with the edge of the workpiece edge

2. Electronic Edge Finders

• Uses electrical conductivity to detect the edge of a conductive workpiece

• Typically includes LED indicators, audible signals, or both for clear edge detection

Shapes & Sizes of Edge Finders

Edge finders come in various sizes and tip designs to accommodate different workpiece shapes.  At Travers Tool Co., we offer the following options:

1. .200” Tip Diameter on a 3/8” or 1/2” Body

• Ideal for smaller and more precise setups

• The 1/2” body provides more tip offset  

2. .375” (3/8”) Tip Diameter on a 3/8” Body

• A common choice for general machining

• Suitable for finding the center of a round tube or solid rod

3. .500” (1/2”) Tip Diameter on a 1/2” Body

• Provides more contact area for larger workpieces

• Offers more tip offset than the 3/8” body size

• Suitable for finding the center of a round tube or solid rod

4. Pointed Tip on a 3/8” or 1/2” Body

• Often used for finding the center of a round tube or solid rod

• The 1/2” body provides more tip offset

How to Find the Edge of a Workpiece with an Edge Finder

Here’s a step-by-step guide to help you use a mechanical edge finder effectively and avoid common mistakes:

1. Secure the Workpiece:

   Ensure the workpiece is properly clamped in the milling machine.

2. Insert the Edge Finder:

   Mount it in the spindle and set it to an appropriate speed (approximately 1,000 RPM for mechanical types).

3. Approach the Workpiece Edge:

   Slowly move the tool toward the workpiece, allowing the tip to contact the surface.

4. Watch for Deflection:

   For mechanical edge finders, the tip will “kick” or offset when contact is made. 

   
   

5. Set the Zero Point:

   At the moment of deflection, set the machine’s DRO (digital readout) or dial reading to zero.

6. Confirm the Setting:

   Move the Edge Finder away from the workpiece, then slowly back in, to confirm your zero setting. 

7. Compensate for Tip Radius:

   Add (or subtract) half the tip diameter (e.g., 0.100” for a .200” tip) to set the DRO or dial to the true zero. 

How to Find the Center of a Boss, Pocket, Round Tube, or Solid Rod

To locate the center of a symmetrical or round feature:

1. Follow edge-finding steps 1 through 6 above:
   
   

2. Move to the Opposite Edge:

   Repeat the edge-finding process on the opposite side without resetting the zero.

3. Calculate the Midpoint:

   Subtract the first reading from the second and divide by two.

4. Reposition:

   Move the machine table to the midpoint value and reset your DRO or dial to zero.

To Find the Center of a Round Tube or Solid Rod

Process:

Use the same process described in the “How to Find the Center…” section above.

TOOL RECOMMENDATION:

To properly position the edge finder along the side of a round workpiece, use either a cylindrical edge finder with a tip diameter equal to its body diameter or one with a cone-shaped tip.

Alternative Tools for Edge and Center Finding

While edge finders are a go-to solution for many machinists, other tools and methods are also available, each with its own process:

• Test Indicators:

  Ideal for high-precision setups but require careful positioning

• Co-Ax Indicators:

  Excellent for centering on bores

• 3D Tasters:

  Digital touch probes for fast X, Y, and Z detection

• Wiggler Sets:

  Suitable for general alignment tasks

• “Chairs” (Custom Fixtures):

  Use a method similar to that described in “How to Find the Center…”

• Center Finders:

  Specifically designed for locating the center of round stock

Conclusion

An edge finder is a crucial tool for machinists seeking precision, accuracy, and repeatability in their work. At Travers Tool Co., we provide a variety of high-quality edge finders in different styles, sizes, and configurations to suit your machining needs. By selecting the right tool and following proper techniques, you can ensure accurate positioning and enhance overall machining efficiency.

Shop Edge Finders and More

Explore our complete selection of edge finders, indicators, and other precision tools:

• Manual Edge Finders & Locators

• Combo Sets

• Electronic Edge Finders & Tool Setters

• Audible Edge Finders

• “Chair” Edge Finder Fixture

• Co-Ax Indicators

• 3D Tasters

• Center Finder

• Wiggler Sets