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Knife Knowledge - Slip Joint Knives

Posted by David McHan

An important safety feature for any knife is the locking mechanism. A good knife should open and close when YOU want it to, which is what the locking mechanism controls. There are many locking mechanisms used by manufacturers, and each has their own pros and cons. Over a series of posts, we'll discuss the different types of locking mechanisms ABKT uses and why we use them.

Slip Joints

Our first focus will be slip joint knives, which we use on the traditional style knives in our Roper and Cattleman lines. These are mostly used in our stockman, trapper, and toothpick patterns.

Here are a few examples of ABKT knives that use slip joints:

Medium Stockman
Trapper
Medium Trapper
Toothpick

Farriers Knife
Stockman
Trapper

Pros and Cons of Slip Joints

There are many benefits from using a slip joint knife. For one, they are easier to manufacture and that translates to being easier on the wallet. They are collected, traded, and gifted more than any other style of knife made. Slip joints are also highly versatile in their blade configurations. They can accommodate different steels, number of blades, and nearly any handle material or design. They are also lighter and easy to carry, varying in size to fit different styles a customer may need.

Ready for some knife jargon? The “snap” noise when opening and closing a blade is called the "walk and talk" of the knife. We design and manufacture our knives to ensure that every slip joint knife talks to the customer.

Another benefit to slip joint knives are their legality. This style of knife is legal in most areas including but not limited to all US states, Europe, and Canada. Of course, we always recommend to regularly check your knife laws because they can change.

One drawback to slip joint knives is that they do not actually lock - so you must take care to use the knife properly. This style of knife is not a pry bar or a chopper. It very well suited to cutting string, whittling, castrating, and/or light use cutting. You must use both hands to open this style of knife, so it may not be ideal for quick use.

These styles of slip joint knives are great for carrying and are a farmer's go-to Sunday church knife. In east Tennessee, where ABKT calls home, you'd be hard pressed to find someone without one of these in their pocket.

How They Work

In simple terms, a slip joint knife has a metal bar spring that holds the blade open and closed. The spring sits along the spine of the knife, pinned to the handle in the middle of the spine. The unpinned section near the blade applies pressure to the bottom of the blade tang, which holds the knife either open or closed.

As you pull the blade open, the spring presses upward. Once fully opened, the spring presses into a slot in the blade tang, holding the blade open. Closing the blade requires enough force to overcome the spring tension on the blade. Additionally, when the blade is near closed the spring tension will close the blade the rest of the way.

Safety tip: Because the blade is not locked, you must be careful how you use the knife to avoid accidentally closing the blade on your finger.

Knife Care Tip: Keep the notch on the tang from getting filled with dirt and grime. If enough material builds up in the notch, the spring won’t engage all the way and the blade will be more likely to accidentally close. Also, slip joints may become difficult to open over time unless you regularly oil the pivot and clean out dirt.

ABKT tests each of our slip joint knives to ensure they meet our quality standards. We cycle new designs up to 100,000 cycles on our cycle tester. Check out the video below to see our cycle tester in action.

We also inspect each knife according to the following criteria:

  1. All blades must snap shut and stay closed to verify the strength of the spring.
  2. All handles and back springs must be smoothly finished.
  3. No gaps in the back springs or handle when finished.
  4. Blades must be sharp.
  5. All Nail Nitches must be visible when closed.
  6. No blades edges or tips should be showing when blades are closed.
  7. All blades must be straight.
  8. Carbon Steel blades must be covered with oil, wrapped in wax paper, and a desiccant package placed in box when shipped.

ABKT started it business 13 years ago making slip joint knives. They are the everyday knife for farmers and cowboys, and are the most collected style among knife collectors. For more information about stockman style knives (which traditionally use slip joint mechanisms), be sure to check out our Guide to Stockmans blog post. We will post in the future about our other locking mechanisms.