Things You'll Need
Ruler
Paper
Pencil
Textron's line of Torx-head bits and screwdrivers are designed to be used specifically with Torx-head screws. The bits are six-point splines, the individual sizes of which are measured in a standard known as "T-sizes." If you ever come across a Torx bit that's mislabeled or doesn't have a T-size on it, you can figure out the exact T-size with a ruler and a chart from Textron.
Step 1
Line up the ruler on the star-shaped screw tip to measure from one point to the point directly opposite.
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Step 2
Examine the markings on the ruler and write them down.
Step 3
Compare the measurement with the "P to P" (point to point) column of the first chart on the Wiha website to determine your Torx bit's exact T-size. You can measure in inches or millimeters. The Wiha link can be found in Resources.
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