A snap-off blade knife (Dutch: breekmes) is a utility knife fitted with a segmented blade that can be snapped off section by section to expose a fresh, sharp cutting edge. It is one of the most commonly used hand tools on construction sites, in workshops, and for general-purpose cutting tasks.
How a snap-off blade knife works
The blade is made from hardened carbon steel and features scored lines at regular intervals, typically every 10-12 mm. When the tip becomes dull:
- Extend the blade until one segment protrudes past the body
- Grip the dull segment with the built-in snap cap or a pair of pliers
- Bend the segment sideways along the scored line until it breaks off cleanly
- The next segment now forms a fresh, sharp point
Most standard blades have 7 to 13 snap-off segments, providing multiple fresh edges from a single blade.
Common blade sizes
| Width | Typical use |
|---|---|
| **9 mm** | Light-duty work: paper, tape, thin cardboard |
| **18 mm** | General construction: plasterboard, carpet, insulation, roofing felt |
| **25 mm** | Heavy-duty work: thick insulation boards, vinyl flooring, rubber sheeting |
Safety tips
- Always retract the blade into the handle when not in use
- Cut away from your body and keep hands behind the blade
- Dispose of snapped-off segments in a sealed container, never loose in a toolbox
- Replace the entire blade when only one or two segments remain for stable cutting
- Use a blade with a blade lock to prevent accidental retraction during cuts
Application
Snap-off blade knives are indispensable on construction sites for cutting plasterboard, insulation material, vapour barriers, carpet, and packaging. They are equally useful in painting and decorating for trimming wallpaper and masking tape. Their low cost and disposable blade design make them a practical alternative to fixed-blade utility knives.
Related Terms
- Utility knife
- Hooked blade knife
- Plasterboard knife
- Cutting mat
- Safety knife
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