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There are a vast number of different types of locking systems that can be found on today's knives. Rather than try to provide a comprehensive listing of each one, I have chosen to focus on those which are most commonly seen and will represent the great majority of knives currently available. |
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Liner lock
Without question, one of the most popular style of lock seen on today’s folding knives is the liner lock. Invented in 1980 by Knife maker Michael Walker, the mechanism was known for some time as a "Walker Lock". Soon enough the design was adopted by mainstream knife manufacturers and the term liner lock was developed.
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| In its most common configuration, the liner lock is created from the steel liners most knives incorporate. Typically cut from the liner on the reverse side of the knife (when looking at knife, blade tip pointing left and edge facing up), a section of the liner on this side is bent away and angled inward toward the interior of the knife. This section of liner bending inward is given a natural "set" in this shape so its "at ease" position is angling away from the liner from which it is cut and cutting across the interior section of the knife handle. The liner now can only go back to its old position with manual force. |
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Bob's Knife and Tools Reviews
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The end of the liner lock which is closest to the blade is cut so as to engage with the bottom end of the blade below the pivot. This bottom end of the blade is cut at an angle so the liner moves across the blade bottom to the point at which the angle stops its movement (ideally in the middle of the blade). The blade is now said to be locked in the open position. To disengage the lock, one must manually move the liner to the side, away from the blade bottom before closing the blade. Once closed, the presence of the blade prevents the liner from moving, but when the blade is opened, the tension in the steel snaps the liner open, stopping at the point where the bottom end of the blade angle prevents further travel. The blade is now open and locked again.
The liner lock was a great advancement in knife lock technology and assisted in the evolution of the tactical knife and one-handed knife. There is debate about the strength of the liner lock. Those who keep their distance from it or claim it is prone to failure often cite examples of the end of the liner being forced off the angled blade bottom as reverse pressure is applied to the blade (pressure on the blade spine). This type of failure is not an inherent weakness of the liner lock design, but rather a function of a poorly made example of it. A well made liner lock, of sufficient thickness and with a sufficient amount of "spring", will push itself into the angled blade bottom and not move until it is made to move by the user. There is no reason to label the liner lock design as weak when in fact a strong and dependable lock under normal stresses.
Some contend the liner lock is not as strong as the back lock based on tests in which various back locks have been shown to withstand hundreds of pounds of weight without failing, which the liner lock cannot do. It is true, the back lock beats the liner lock in these kinds of brute strength tests and if your knife needs to withstand that type of pressure you should consider this. However, most normal use does not rise to this level and by limiting oneself to good quality manufacturers, a user can rest assured that his hand is well protected by a liner lock.
Frame lock
A frame lock system is similar to a liner lock however the knife with a frame lock typically does not have handle scales but rather is a simple frame design in which the two sides of the handle are, alone, the basis of both the frame and handle. The two sides of the handle form the frame and are often made from steel cut thicker than what any traditional liner lock would be. It is this thickness from which the frame lock draws its considerable strength. In other respects, the frame lock functions very much like a liner lock. A portion of the frame which makes up one side of the knife handle is cut and given a set so it angles inward toward the interior of the handle with the tip engaging the bottom of the blade which has been cut at an angle like a ramp. It is released by applying pressure to move the piece of frame away from the blade bottom and back toward its natural side and is held in place there by closing the blade. Upon opening, the tension the lock piece has been given causes it to snap across the bottom of the blade engaging at its furthest point of travel as determined by the angle cut into the blade bottom.
As stated before, this is a very strong type of lock due to the thickness of the materials generally being used however, like the liner lock, requires quality construction to realize its full potential. A mismatch between the angle of the blade bottom and the tip of the lock which causes the lock to travel too far or not far enough can have serious effects on the effectiveness of the lock.
Lock back
The lock back knife design has been around for many years and is older than the liner lock design. This well proven design functions with a locking arm along the handle spine being shaped with a hook or post end that fits, under spring pressure, into a notch on the back of the blade behind the pivot.
The lock back, having been around for many years and proven itself dependable, has many adherents. The lock back is the simplest and least expensive lock to manufacture and enjoys a general familiarity among the knife using public as it has grandfathered itself into the knife landscape over time. This type of lock is found most often on traditional, light to medium duty folding knives such as the Buck 110 or smaller gentleman’s knives based on similar patterns and incorporated the release near the butt end of the knife.
As with anything else, the quality of construction in the lock back is vital. The lock back design operates under tension from the back spring and every time the knife is opened the hook is dragged with tension across the notch edge to then "snap" into place. The use of low quality steel in this construction can eventually see a rounding off of the hook and notch due to wear from opening. This will weaken the lock and increase the likelihood of failure. Some claim the lock back is more susceptible to lint and dirt driven failure than other types of locks as this debris can collect in the hook and notch system thus preventing full engagement. Poor construction which allows play or wiggle in the blade can also reduce the effectiveness of a lock back. The lock back release is located on the spine at the furthest point from the blade and is operated by pressing downward on it. A lock back knife is not a true one-handed knife. Although a lock back can be closed with one hand by releasing the lock and pressuring the blade spine against something, like the side of your leg, this is not true one-handed design.
Mid lock
The mid lock is really a back lock except with the release located in the middle of the handle spine as opposed to near the butt end of the knife. With the locking arm shortened the back lock can be made to tighter tensions and thus increased effectiveness and strength. Most notably among mid lock knives are the video demonstrations produced by Cold Steel which show them maintaining integrity under sometimes hundreds of pound of pressure. These demonstrations speak well of the mid lock design and show it can achieve remarkable feats of strength.
AXIS lock
The AXIS lock is the brainchild of the design team at Benchmade Knives. In this system a reinforced steel stop pin spans the entire width of the knife. The pin rides fore and aft in a slot cut through the liners and handle scales, creating a "see through" slot just behind and above the pivot. When the blade is opened the stop pin cams rearward in the slot, riding the rounded bottom of the blade until the blade approaches the open position. At this point the rounded bottom of the blade flattens to an incline ramping upward. The stop pin, driven by omega springs, now slides up this inclined portion of the blade with the final open position leaving the stop pin forward in its slot on the top flat inclined portion of the blade, thus preventing the blade from rotating closed. To close the blade, the stop pin must be pulled rearward to clear the flat inclined portion and then the blade can be closed.
The advantages of this system are numerous. Firstly, the strength of the lock is undisputed. The blade is fully blocked from rotating closed by a substantial reinforced steel pin held in place by the liners and ultimately the entire frame of the knife. The lock is easy to operate, it is one-handed and fully ambidextrous. I have not heard anything negative about this lock and the knives I own with this type of lock have always worked very well.
Ring Lock or Twist lock
Several knife manufacturers have utilized this type of locking system on their knives, the most notable being Opinel Knives who added it to their line in 1955. Simple but highly effective, this lock system has proven its popularity due to its ease of use, dependability and low cost.
To operate, the user turns a metal ring or ferrule wrapped around the pivot of the knife to a position where a break in the ring allows the blade to be opened. Once opened, the ring is turned again so the channel through which the blade was opened is once again blocked, thus locking the knife in the open position.
Slip joint
The slip joint lock is not really a "lock" in the technical sense but rather is simply a description of the method by which a knife blade is kept open through spring tension. The slip joint is found on traditional pocket knives and is perhaps the oldest design still widely available.
The slip joint pocket knife has a stiff back spring which is a piece of steel riveted to the handle. As the knife blade is opened, the back spring is forced outward by the rotation of the blade and returns to rest in its original position once the blade is fully open. The only force keeping the blade open at this point is the pressure of the back spring on the blade. To close the knife, this force is overcome by exerting greater force on the blade spine and closing the knife. There is nothing to disengage or maneuver, the slip joint is a tension only system.
While it may not qualify technically as a lock in the true sense, the back spring does keep the blade open during normal use and prevents opening while closed so it carries out a critical function and is worthy of inclusion here.
Lever lock
A lever lock is a system whereby a post or pin contained in or near the pivot bolster engages a hole drilled in the base of the blade. With the pin through the blade hole, the blade is locked either in the open or closed position. This is a lock use on automatic knives and is closely related to the plunge lock.
A similar locking system is one in which the blade is manufactured with a post on its spine down near the pivot. The back spring has a circular top piece with a hole drilled in it to match the post. When the blade is opened, the post engages into the hole in the back spring and a very firm and safe lockup results.
Clasp Lock
Considered more of an antique type of lock, this was found on knives at the turn of the century. The simple clasp lock featured a tension loaded piece of metal on the spine of the handle at the pivot. When the blade was opened it would force the clasp upward, much as in the slip joint knife. When the blade was fully open, the clasp would return to its original position due to the spring tension. The clasp lock is released by a lever or sometimes just a simple ring that is pulled away from the knife to release the blade.
Some variations of the clasp lock contained an additional "post in groove" system to enhance the lock beyond simple tension. One of the most famous clasp locks was used on the Navaja knife which incorporated a series of posts which ratcheted through the clasp and make a clicking sound as each passed. This sound became famous as the Navaja "Carraca" sound and if heard in the darkness, was a cause for alarm.
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