The Pentagon OTF is a new American-made double-action out-the-front (OTF) automatic knife from Studies and Observations Group (SOG). It’s designed with the professional in mind for demanding use. It’s SOG’s first OTF knife and was several years in development. Fans of SOG knives have been clamoring for the company to come out with an OTF knife. SOG waited to release one until the company could do it right. The Pentagon OTF proves that the wait was well worth it. SOG did it right.

The Pentagon OTF is engineered with SOG’s patent-pending Dynamic Locking System blade lockup. It’s guaranteed to withstand thousands of openings and closings without blade rattle or the need for factory re-calibration. It offers exceptional lockup strength.

SOG is no newcomer to the tactical knife game. SOG was founded in 1986 by designer and toolmaker Spencer Frazer. Named after the elite Vietnam-era multiservice special operations unit. known as the Military Assistance Command, Vietnam Studies and Observation Group (MACV-SOG), the company’s first knife was a replica of the original MACV-SOG Counter Insurgency Support Office (CISO) issue Bowie knife. The new SOG Pentagon OTF is a fitting addition to the company’s now extensive line. SOG was recently acquired by GSM Outdoors.

SOG Pentagon OTF has a 3.79” CPM S35VN double-edge dagger-style blade. Dynamic locking system ensures secure, rattle-free lockup and no re-calibration. The double-action is smooth and authoritative.

OTF Automatic Knives

OTF Automatic knives fall into one of two types single-action and double-action. The blade on single-action OTF knives must be manually retracted after deployment. Double-action OTF knives have a mechanism that automatically deploys and retracts the blade.

The blade doesn’t have enough force during deployment to penetrate through an object. What will happen is the blade will disengage from its track if it comes in contact with an object while deploying or retracting. This is a safety feature. Resetting the blade is easy and takes only seconds. You simply pull the blade to the full extension and then give it a sharp tug to reengage the blade to the deployment track.

OTF knives have several advantages over side-opening folders, whether manual or automatic. A key advantage is that they allow you to maintain a full, firm grip on the knife during deployment. You don’t have to adjust your grip. This can be critical is self-defense uses. They allow for quick one-handed deployment. They can’t accidentally close on your fingers. And double-action automatic OTF knives allow for easy one-handed blade closure, as well.  They’re a great adult fidget toy too, as many who own one will attest.

Maintenance of an OTF knife is really not that different from that of a folder. Clean the blade after use. Remove any residue left after cutting before retracting the blade. Regularly lubricate the blade with a light lubricant. I recommend the use of a dry lubricant such as SENTRY Tuf-Glide™. Tuf-Glide won’t attract dust, dirt or debris or gum up the action, ensuring reliable operation. Never put gun oil or any liquid directly into the handle. If you want to clean out the inside of your knife you can use compressed air. Don’t disassemble the knife. It will void the warranty.

SOG Pentagon OTF

The SOG Pentagon OTF is a hefty knife that’s built for hard-use duty. It features a 3.79″ flat-ground plain double-edge spear-point blade made of CRYO CPM® S35VN stainless steel with a hard, wear-resistant stealthy matte black PVD coating. Titanium nitride is a functional coating that protects the blade and provides lubricity. The blade has a fuller (often erroneously referred to as a “blood groove’) on each side for added aesthetic appeal. Blade width is 0.75″. Blade thickness is 0.11”. The Pentagon OTF has an overall length of 9.08” when open and measures 5.28” when closed. It weighs in at 6.7oz.

SOG Pentagon OTF’s oversized slide button allows for multiple interface points. Hard anodized 7075-T6 aluminum hand is easy to hold, even with gloves. Ambidextrous design allows easy operation with either hand.

The handle is CNC machined from 6061-T6 aluminum and hardcoat anodized (MIL-A 8625 Type III). It’s available in two colorways – Blackout and Flat Dark Earth (FDE). Both colorways have black hardware. The handle features ample contouring and texturing that provide a comfortable and solid non-slip grip. The machined micro-texture surface provides the right amount of grip in the right places without being so aggressive as to abrade your hand or wear out your pocket. The symmetrical handle design allows for use with any grip or blade orientation. The handle has two opposing finger grooves that serve as a dual guard   There’s an inobtrusive stainless stainless-steel tip-down carry pocket clip that’s suitable for ambidextrous carry. There are are no hotspots. The pocket clip and handle screws are stainless steel T6 TORX® screws. 

A few words on the blade steel. CPM S35VN a high-end martensitic stainless steel. Made in the USA by by Crucible Industries using the patented Crucible Particle Metallurgy (CPM) process. CPM is a method of producing higher alloyed grades of superior quality than could be accomplished through conventional melting processes. It produces a micro-structure that is fine grained and homogeneous.

CPM S35VN is a tougher version of the popular CPM S30V. The vanadium was reduced from 4 to 3% and replaced with 0.5% niobium. It offers what many consider the best combination of toughness, wear resistance, and corrosion resistance. It offers better resistance to chipping than CPM S30V. while maintaining nearly the same edge retention and ease of sharpening.

The steel is important, but it’s only part of the performance equation. The heat treatment is as important as the steel, if not more so. SOG utilizes a unique computer-controlled cryogenic heat treatment process that maximizes the performance of the blade.

The blade is deployed and retracted by means of side-mounted oversized slide button. The slide button is made of blackened stainless steel and has multiple interface points that allow for the leverage needed for reliable activation. The design of the slide-button coupled with the side-mounting allows for rapid ambidextrous opening, even while under duress or when wearing heavy gloves. The slide button requires a good amount of effort to deploy and retract the blade. There’s no worry about accidental deployment.

Blade play (wiggle) is present to varying degrees with nearly all out-the-front knives. SOG has addressed this issue with its Dynamic Locking System blade lockup. It ensures that the blade moves quickly to the open or closed position. When there the blade is held firmly in place in a reliable, rattle-free lockup. There’s virtually no blade play. The only other out-the-front knives with no blade play that I am aware of are the Hawk Custom Deadlock OTF knives which start at $1,000.00.

So exactly how does it work? The basic sequence of operation of the Pentagon OTF from the closed to open position as the slide button is pushed forward is as follows:

SOG Pentagon OTF is equipped with an inobtrusive stainless steel pocket clip. The clip is mounted for tip-down carry and works for ambidextrous use.

1. Springs build up force
2. Lock is released
3. Dynamic locking feature is opened
4. Blade travels from closed to open position
5. Locking feature is engaged
6. Dynamic locking feature is engaged

The basic sequence of operation of the Pentagon OTF from the open to closed position as the slide button is pulled rearward is as follows:

1. Springs build up force
2. Lock is released
3. Blade travels from open to closed position
4. Locking feature is engaged

The operation of the Pentagon OTF is similar to other double-action OTF knives except for the dynamic locking feature. This feature is unique to the Pentagon OTF. It employs what SOG refers to as “button over-push” to open up the dynamic locking feature and keep it open long enough for the blade to be fully deployed. When the slide button is released that in turn releases the force necessary to hold the dynamic locking feature open and it clamps down on the regularly locked blade and eliminates blade play.

My Thoughts

SOG has raised the bar for OTF knives with the Pentagon OTF. As of this writing, I have been carrying the Pentagon OTF regularly for several months. There have been no issues. The knife has worked flawlessly. Design, materials and workmanship are outstanding. It has excellent ergonomics and an aesthetically appealing form factor. It’s not a lightweight knife, but that goes with the territory. 

The Pentagon OTF has performed exactly as advertised. The Dynamic Locking System works very well. As previously mentioned, there’s no perceptible blade play when the knife is open. There isn’t any rattle when the knife is closed. The blade deploys and retracts with authority.

As would be expected, the Pentagon OTF isn’t inexpensive. It has a MSRP of $349.95. As with all SOG knives, it comes with a Limited Lifetime Warranty.  If you are looking for a great automatic OTF knife, you’ll definitely want to check out the SOG Pentagon OTF.

SOG Pentagon OTF

Maker: SOG Specialty Knives & Tools
Model: Pentagon OTF
Type: Double-Action OTF Automatic Knife
Overall length: 9.08″
Closed Length: 4.06″
Blade Length: 3.79″
Blade Width: 0.75″
Blade Thickness: 0.11″
Weight: 6.7oz.
Blade Steel Type: CRYO CPM S35VN Stainless Steel
Blade Finish: Black Titanium Nitride
Edge Type: Plain Double-Edge
Blade Shape: Spear Point
Handle Material: 6061-T6 Aluminum, Hardcoat Anodized / MIL-A 8625 Type III
Handle Color: Blackout or Flat Dark Earth (FDE)
Opening Mechanism: Automatic OTF Switch
Locking Mechanism: Dynamic Locking Mechanism
Pocket Clip: Stainless Steel, Tip-Down Carry
Country of Origin: USA
Warranty: Limited Lifetime
MSRP: $349.95


SOG Knives

Material Disclosure

I received this product as a courtesy from the manufacturer so I could test it and give my honest feedback. I am not bound by any written, verbal or implied contract to give this product a good review. All opinions are my own and are based off my personal experience with the product.

*The views and opinions expressed on this website are solely those of the original authors and contributors. These views and opinions do not necessarily represent those of Spotter Up Magazine, the administrative staff, and/or any/all contributors to this site.

By Eugene Nielsen

Eugene Nielsen provides intelligence and security consulting services. He has a bachelor's degree in political science from the University of California. His byline has appeared in numerous national and international journals and magazines.

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