What I look for before purchasing a folding knife.

 What I look for in a folding knife BEFORE I buy it.

From Left to right (as seen above): Kubey Max Tkachuk Design (liner lock); SOG Terminus XR (axis/roller lock); SRM 258L-GB & -GN (axis/roller lock); FKMD Predator 1 FX-446 ODS & FX-446 GR (Liner locks/LAWKS system); Nieto Fighter (traditional lock back) and Extrema Ratio RAOC (roller/axis lock).

Let's grab a coffee and get started?

These are the following things I look for in folder before I purchase it.

The lock up

Perfect lock up regardless of the mechanism and what materials the knife has been made from (In other words don't be swayed if the whole construction is from Titanium etc.- it doesn't make the knife) although more important for liner locks and frame locking mechanisms.

A thorough lock up can be seen in the above example of a liner locking type folder

(knife shown is the Kubey Max Tkachuk Design in AUS10, G10 and Titanium)

 Above example shows a "roller" type "axis"  lock bar mechanism (SRM 258L-GN). Some say patented/pioneered by benchmade. Whether that is/was the case is not the subject of this blog. Numerous knife manufacturers (and not just Asian) as using such a design.

All frame locks must have a removable hardened steel insert at the end of the lock bar in order to be able to replace it after wearing.

(I own one frame locking knife and it's not with me right now- a very good one from RaidOps)

For liner locking knives, if the liner barely engages the back end of the blade then that is it for me, I'll put it back on the shop's shelf and call it a day or look at some other models. 

I don't care if it is made of printed titanium alloys and sports a 154CM blade cryo treated on Mars, it means nothing if the lock up is poor, simply because you may as well be purchasing a slip jointed knife. If you have to fiddle with the locking mechanism right after you purchase it ir even before hand then the locking mechanism was rubbish, end of story.

For example on certain FKMD folders, the back end of the blade which engages the locking liner has been treated in such a way (it appears to some sort of EDM but I'm not sure and it's probably a manufacturing "secrete") as to provide extra long lasting friction between it's surface and that of the end of the liner, 

(Above example from FKMD FX-446 ODS)

so that when under pressure the liner will not want to move back across the back end of the blade and thus disengage under heavy reverse loading (ie trying to close the blade whilst it is locked open). Small design features like this only add a an "extra" when I'm looking to purchase. I guess this is why I own 2 of such folders.

Also it is indeed possible to be "overbuilt" but still of small structure as can be seen here (see image below) in this FKMD folder which sports very thick liners (almost 2mm!) and even a very thick lanyard pin!).

(Above example from FKMD FX-446 GR)

What about the actual frame of the knife?

A partially closed back or fully closed back. Generally all classical lock back knife designs 

Above, classical lock back knife design. (Nieto "Fighter" in Sandvik 12C27)

have a fully closed back due to the way the locking mechanism is constructed, and despite the plethora of locking mechanisms out there, this type of lock design and or slight modifications of it has stood the test of time.

An example of a "partially closed back" (Extrema Ratio HF1T now currently discontinued)

Above image showing a range of folders from medium sized to large.

From Left to Right: Partial, Partial, Fully closed back (single one piece 'Mono Chassis" design new from SRM Outdoors), Fully closed back and Fully closed back; 

Personally, I'm not a super fan of the pillar type standoffs (Eg TB outdoor, a French company are still making knives like this it's a cheap way to make a folding knife (I thoroughly checked them out at IWA 2024 and personally didn't like them and don't believe they would go the distance as military knives (as many models are marketed as-yeah maybe if the soldier doesn't have to purchase it themselves and it's a freeby) as they provide the least amount of contact for the knife scales/body. besides this, it's an "Old fashioned way" now of folding knife construction IMHO.

Although this type of "pillar/standoff" construction) probably makes for the lightest possible construction although it could also be argued that there are more screws and or bolts involved. To be honest the only folders which have ever failed me were ones constructed in this manner when a small screw came loose and the frame scales started to move and this only caused other screws to loosen. With CNC bending machines folding knives can be constructed without

Medium to large, it doesn't matter your preference, as long as you don't buy a folder and have to continually fiddle with it to get it to work properly. Ok maybe you like pulling apart your folders and fiddling with them, personally I don't want to have to buy something and pull it apart all the time (ok, with few exceptions-maybe tuning a car?)

Small to ginormous range of folding knives Far right knife (Extrema Ratio RAOII "Expeditions model).

Note, that despite the the slight variation in handle sizes, the blades shown above are all pretty much similar in length and thickness.

I could be argued however that the pillar construction allows for easier cleaning of a folding knife.

The mechanism by which the blade is prevented from moving upwards when downward pressure applied. 

Generally, this is referred to as a stop pin; 

(see below) A super thick stop pin sandwiched between two almost 2mm thick liners.

where a horizontal circular cross section pin will be inserted between the two liners. (this is absent in the radically new designed "mono-chassis" from SRM-where the chassis forms also part of the "regular" stop pin.

How thick is this pin? How thick are the liners to which this pin is inserted? 

The stop pin or stop mechanism should be adequate for the knife design. Under a pressure of at least up to 30kg it should not fail. It should not be so thick as to stop a ten tonne truck. The knife world is full of over designs whereby any such attempts by the user to fulfil gigantic and ridiculously disproportionate loads upon a folding knife would result in severe injury to the user's arm/hands before any collapse of the folding knife's mechanisms-in reality.