TOOL
Binding router bit
Cuts the channel that takes the binding and purfling.
| Cutter diameter | 6 – 12 mm, often a spiral upcut |
|---|---|
| Bearing sizes | Matched set, 0.5 mm increments |
| Cut depth | Matched to the binding thickness |
| Channel width | Binding width plus a little for glue |
| Shank | 6 mm or 1/4 in |
| Setup | Router table or a binding jig with a carriage |
| Channel depth | Binding thickness, plus 0.2 mm for glue |
|---|---|
| Channel width | Binding plus purfling width |
| Cutting | Shallow passes, working around the body |
| Direction | Feed against the cutter rotation |
| Test | Cut a scrap to check depth before the instrument |
| Price band | Moderate |
A binding router bit has a bearing that rides against the side of the body and a cutter that removes a channel of a set width and depth. The binding sits in that channel and protects the vulnerable edge of the top and back, where end grain meets impact.
The bearing size sets the depth of the channel and the cutter height sets its width. Most builders use a set of matched bearings so a top and back channel, and a purfling ledge inside it, can all be cut without changing the bit.
At this stage
The channel is cut after the box is closed and the top and back are trimmed flush. The bearing rides on the side, so the side has to be smooth and true first.
Suits these instruments
- Steel-string acoustic
- Classical
- Archtop
Works with
- Binding and purfling
- Body mold
- Titebond
- Cabinet scraper
- A router cutter spinning at 20000 rpm is the most dangerous tool in the shop. Eye and hearing protection, no loose clothing, and hands well clear.
- Cut in shallow passes. A full-depth cut in one pass grabs the work and throws it.
Working notes
- Make a test cut in scrap every time you change a bearing.
- Support the body fully so it cannot tip into the cutter.
- A spiral upcut bit clears chips better and leaves a cleaner channel in end grain.
- Cut the purfling ledge in a second pass with a smaller bearing, not a wider bit.
Related
Bracing chisel
Shapes braces to a measured taper without tearing the grain.
Spokeshave
Shapes curved surfaces a plane cannot reach.
Radius dish
Gives the top and back their curve, consistently.
Go-bar deck
Clamps a whole braced plate at once, evenly.