All conditions
Condition
Gap or poor fit
The parts do not meet flush — a worn tenon, a chipped break — and the adhesive must bridge the gap.
What to do
Working with it
- Measure the gap. Under about 0.1 mm any glue works; past 0.5 mm only a gap-filling adhesive has anything to bond to.
- Thin, watery adhesives are the worst choice here — super glue in a gap cures into a brittle crust that snaps.
- Epoxy, polyurethane, and construction adhesive all bridge gaps. Epoxy stays dimensionally stable; polyurethane foams and must be trimmed.
Adhesives
What holds up, and what doesn’t
Better under this condition
Ruled out by it
Questions
Common questions
- Should I clamp a gap closed or fill it with adhesive?
- Clamp only when the parts naturally return to the correct shape without harmful stress. If closing the gap bends or distorts them, rebuild the missing fit or use an adhesive designed to remain sound at that thickness.
- Does expanding glue turn a loose joint into a strong joint?
- Expansion can fill empty space, but the cured foam is weaker than a thin bond between fitted faces. The repair still needs solid contact areas that carry the load.
- Can adhesive replace a missing chip or worn joint surface?
- A small defect may be rebuilt with a suitable filled resin, but a large missing bearing surface should be patched with compatible solid material first. Glue works best between parts; it is a poor substitute for the part itself.
- How do I prepare the inside of an irregular gap for glue?
- Remove loose fragments, dust, oil, and weak old adhesive from every reachable face. A gap-filling product can match the shape, but it cannot rescue a bond attached to contamination or crumbling material.