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Tap
From WikiPedalia
A tap is a tool for cutting internal threads. It takes the form of a bolt with flutes cut in the threads, and usually has a taper at the end that is intended to start the thread. There are only a few standard sizes used on bicycles:
| Size | Application | Metric drill | SAE drill |
|---|---|---|---|
| 3 mm | Adjusters in rear dropouts | ||
| 5 mm x .8 mm | Bottle cage mounts, fender eyelets, shift lever bosses. | 4.20 |
|
| 6 mm x 1mm | Cantilever bosses, some fender eyelets | 5 mm |
|
| 10 mm x 1mm | Derailer hangers | 9.0 mm | "T" |
| 1/2" x 20 L & R | Pedal threads for one-piece cranks | ||
| 9/16" x 20 L & R | Pedal threads for three-piece cranks | ||
| 1.375 x 24 tpi L & R | British/I.S.O. bottom brackets | ||
| 35 x 1mm L & R | French & Swiss bottom brackets | ||
| 36 x 1mm | Italian bottom brackets |
The corresponding nut-like tool for cutting external threads is called a die.
My Tool Tips series features an article on the use of taps.
