Patented on May 28, 1908, the C.P. Wrench Knife is among the most sought-after of the ancient multitools. Produced in Bristol, Tennessee, it was based upon a self-adjusting pipe wrench, with a knife blade that folded out from the handle. The upper jaw of the wrench head is spring-loaded with a thumb stud for quick opening. Heavy duty all-steel construction makes the C.P. tool a real workhorse. It also makes the tool ride rather heavily in the pocket. A screwdriver tip ground onto the opposite end adds a bit more capability.
The jaws of the C.P. Wrench are somewhat more complex than they first appear. The lower jaw is a hardened carbon steel insert, pinned into place on the frame. The teeth on this jaw are slanted outwards, away from the jaw opening.
The upper jaw pivots and is spring-loaded, allowing pipe of up to 3/4" (19mm) diameter to be gripped securely. The teeth on the upper jaw slant inwards, opposite the lower jaw. By design, the harder a person pushes on the wrench handle, the tighter the jaws bite down and grip the pipe.
Two slabs of heavy cast steel form the basis of the handle. They are riveted together in three places. These rivets also serve as pivots for the upper wrench jaw and knife blade, and attachment point for the lower jaw/backspring. It is an extremely solid construction.
The handle houses a spear point knife blade that is 2-3/4" (70mm) long. No locking mechanism is employed.
A flathead screwdriver tip is ground into the profile of one handle slab, on the end opposite the wrench head. (Note that this flathead driver was the only type required back in 1908)
Unknown, if any.
- Folded length = 5-1/4" (133mm)
- Unfolded length = 8" (203mm)
- Thickness = 3/8" (9.5mm)
- Weight = 7.2 oz (202g)
At least one example of a C.P. Wrench Knife is known to exist with a different cast profile to the wrench jaws than the one pictured above.
Patented 5-28-08. Unknown how long it remained in production, or how many were produced.