Interchangeable Blades for Folding Pocket Tools

A 1987 patent for a folding pocket knife with split handles that can securely swap out different tools, like saw blades, using a locking pivot block and protective aluminum handles.

What it covers

This patent describes a folding multi-tool with two U-shaped handles that swing around to enclose or expose a central blade. It features a mechanism to swap in different tools, such as a saw blade, using a pivoting block with a split (bifurcated) end on one handle. When the handles are closed, a pin on the second handle slides into this split end, locking the interchangeable tool securely in the middle. To prevent the blades from wobbling, built-in centering guides inside each handle hold the tool perfectly aligned. Additionally, the design uses soft aluminum handles with press-fit pivot pins and reinforcing spacers, allowing the user to use the folded tool as a heavy-duty, right-angle screwdriver without scratching or damaging the metal.

What it doesn't cover

• —Does not cover multi-tools with single, solid handles where blades fold out like a traditional Swiss Army knife.
• —Does not cover interchangeable blade systems that do not use a bifurcated pivoting block and mating pin to lock the tool.
• —Does not cover tools that lack centering guides built inside the U-channel of the handles.
• —Does not cover folding knives with steel or titanium handles that do not require protective press-fit reinforcing spacers.

The clever bit

Instead of using a complex latch, the tool uses the natural closing action of the two handles to lock the interchangeable blade. The split end of the pivot block on one handle is physically pinned shut by a post on the opposing handle when they meet.

Why it matters

This patent represents an early innovation in the consumer multi-tool market of the 1980s, trying to solve the problem of carrying multiple heavy tools. By allowing a single handle system to swap out saws, files, and blades, it paved the way for modern modular pocket tools. It also addressed the manufacturing challenge of using lightweight, cheap aluminum instead of heavy steel for the handles.

Real-world examples

• 1.Modular pocket knives with interchangeable saw and knife blades
• 2.Early butterfly-style multi-tools
• 3.Aluminum-handled folding utility knives