TOOL
Body mold
Holds the sides in shape while the box goes together.
| Type | External form, in two halves |
|---|---|
| Material | 18 mm plywood or MDF |
| Construction | Stacked and shaped, or CNC cut |
| Clamping | Open access along the full perimeter |
| Linings | Fitted and glued while the sides are in the mold |
| Alignment | Dowels or bolts to keep the halves registered |
| Tolerance | Sides must sit without forcing |
|---|---|
| Height | Deep enough to support the full side depth |
| Release | Wax or tape the mold so glue does not stick |
| Storage | Flat, so the mold itself does not warp |
| Reuse | One mold, many instruments |
| Price band | Moderate, or built from plans |
A body mold is an internal or external form that holds the bent sides in the correct outline while the top, back and linings are glued on. Without one, bent sides spring back and the body goes out of shape during the build.
Molds are made from plywood or MDF in two halves, with clamping access along the whole perimeter. Most builders own a mold per body shape they build, because the mold defines the outline and the outline defines the instrument.
At this stage
The mold is used from bending through to closing the box. Sides that are bent and then left out of the mold will not go back into the right shape.
Suits these instruments
- Steel-string acoustic
- Classical
- Archtop
Works with
- Bent sides
- Binding router bit
- Titebond
- Radius dish
- A stacked plywood mold is heavy and has sharp edges. Deburr it and lift with two hands.
- Do not force a side into a mold. If it needs force, the bend is wrong and the side will crack.
Working notes
- Line the mold with tape or wax before the first glue-up, and every one after.
- Fit the linings while the sides are clamped in the mold, not after.
- Keep the top and back halves labelled — an upside-down mold builds a mirror image.
- Store molds flat. A warped mold builds a warped guitar.
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.