Heavy Duty Metal Knife

Standard snap-off knives use 18mm blades. A 25mm blade is not merely wider — it is thicker and considerably stiffer, and stiffness is what a knife needs when it is being pushed through thick material. An 18mm blade extended more than a segment or two flexes noticeably under heavy pressure, wanders off a straightedge, and eventually snaps mid-cut. A 25mm blade stays where you point it. For cutting insulation board, thick card and packaging, carpet and underlay, plasterboard, foam and dense sheet materials, that rigidity is the whole difference.

It also reaches deeper. Cutting insulation or foam board means getting through material that is thicker than a small blade can span, and a 25mm blade extended a few segments has the depth to do it in one pass rather than scoring from both sides.

The housing is aluminium alloy with a stainless steel flute. The flute is the channel the blade runs in and it is the part that determines whether the blade is held rigidly — a blade in a worn or sloppy flute rocks and snaps under load. Stainless matters because these knives cut damp materials, insulation and packaging outdoors, and a rusted flute goes rough, which makes the blade stick when advanced; people then force it and it breaks in the channel.

One 25mm blade is included and it takes Harden 570349 blades.

The buyers are insulation and drylining contractors, carpet and flooring fitters, packing and crating departments, shopfitters, roofing contractors, upholsterers, and hardware dealers supplying trades cutting thick material.

Three habits. Extend only as much blade as the material depth actually needs, since even a 25mm blade flexes when most of it is out. Cut away from your body and never towards your supporting hand. And snap segments off with pliers or the cap snapper, holding the piece in a cloth — a 25mm segment is a substantial piece of razor-sharp steel and it flies.

Retract the blade every time you put the knife down. Ask us on WhatsApp for a price, or with a box of 570349 blades.