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Tools & Rules Online -- Fast, Accurate Work Location with Edge Finders
 |  | | Volume 3, No. 1 | Winter, 2009 |
| | | |  Edge Finders are simple, effective and accurate tools for locating workpiece surfaces.
Flat surfaces, straight edges, grooves, shoulders, round work, dowels, studs, center points and scribed lines can all be accurately located with this tool. | How To Use an Edge Finder
Edge finders are easy to use. First, secure them into a collet or chuck. Then, traverse the worktable to obtain contact between the rotating edge finder and the work.
Upon contact, the contact diameter will shift to concentric position relative to the body -- with very slight additional table adjustment, it will move off center with a decided wobble (see right).
When the contact diameter aligns with the shank, the center of the finder is exactly one-half the diameter of the contact from the work edge. After setting the appropriate machine axis, accurate location relative to the workpiece edge is assured.
To locate center points and scribed lines, put a rule or pencil tip along a scribed line. Then, carefully bring the edge finder's pointed contact to the center point or intersection of scribed lines and adjust the table so that it barely touches the work.
Starrett 827 Series Edge Finders
The body and contacts of Starrett 827 Series Edge Finders are made of tool steel, hardened, ground and lapped to close tolerances for diameter and concentricity.
Single edge versions are available in an English version with .375" body and .200" contact diameters, and a Metric version with 10mm body and 6mm contact.
Double Edge models have .500" or 10mm bodies and .200" or 6mm contacts, respectively, on one end, and pointed contacts on the other.
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The Collet Adaptor -- A Valuable Edge Finder Accessory
A recent addition to the Starrett product line, the Collet Adaptor (below) (PT28314, EDP 68846), simplifies edge finder use with when working with multiple collets on vertical milling machines.
 Working as an exterior attachment of the 3/8" shank edge finder, it has progressive steps of 1/4", 5/16", 3/8", 1/2", 5/8", 3/4" and 1" to fit seven common collets, thus eliminating the need to change collets when using the edge finder.
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