SOG BRINGS THE PENTAGON FOLDER INTO THE 21ST CENTURY WITH DESIGN AND MATERIAL UPGRADES
Knives are among man’s oldest tools and oldest defensive weapons. Even in the 21st century, they maintain their utility either as a backup to a firearm or as a primary weapon if you live in an area that makes legally carrying a firearm difficult.
“The Pentagon XR is part of SOG’s professional series and designed for defense, but it makes a great utility blade as well.”
The Pentagon, in both fixed blade and previous folding models, has been a self-defense staple for SOG Knives for years, and its latest incarnation is a thoroughly modern, feature-packed folding version, the SOG Pentagon XR.
If you carry a defensive folder either as a primary weapon or as a backup, then it’s well worth taking a look at what the Pentagon XR has to offer.
WELCOME TO THE PENTAGON
The latest version of the Pentagon has a number of updates over previous models in both design and materials. The XR is named so due to the ambidextrous XR lock, which operates by pulling down on the release lever.
This can be done with the thumb or index finger of either hand. It’s a tough lock capable withstanding 1,500 pounds of pressure, but it’s also easy to operate. This style of lock keeps your hands away from the blade too when you’re closing the knife, unlike frame or liner locks.
The blade itself is 3.61 inches of cryo-treated Carpenter CTS XHP stainless steel. CTS XHP is a powdered metal stainless steel that’s described as either a high hardness 440C stainless steel or a corrosion-resistant D2 tool steel.
SOG doesn’t list the Rockwell hardness on the SOG Pentagon XR, but Carpenter Steel states that it can be treated up to a 64 HRC.
SOG describes the XR as having a spear-point blade with a centerline tip. It’s almost a dagger profile with a dagger-style grind, except that the back edge is unsharpened except for a small portion near the tip.
The factory edge was excellent and hair popping sharp. A thin fuller is present in the blade and everything is coated in a black titanium nitride for even further corrosion resistance and to add to a subdued finish.
OPEN IT FAST
There are three ways to open the SOG Pentagon XR, although one requires some practice. The first way is by means of the spine mounted flipper. It’s fast and intuitive, and a set of serrations on the top edge of the flipper ensures your finger has positive contact when you snap the blade open.
“The factory edge was excellent and hair popping sharp… and everything is coated in a black titanium nitride for even further corrosion resistance…”
The second method is by means of the dual thumb studs on the blade. These are well positioned and make it easy to snap the blade open with a flick of the thumb.
I’m about tied for how fast it is to open the blade with either the thumb studs or the flipper. With my left, I found I was better using the flipper, but then I’m less coordinated with that hand.
With that said, the knife is truly ambidextrous; I just happen to be better with my primary hand than the offhand. If you’re a lefty though, you’ll love the SOG Pentagon XR. The controls are exactly the same on both sides of the knife.
Closing the knife is extremely easy too. Just pull down on the lock with either your thumb, index finger, or both by grabbing it from each side, and give a slight forward flick and the blade rolls closed on its own.
You can do this with one hand and, as mentioned above, your fingers are nowhere near the blade.
The third opening method is to pull down on the XR lock and swing the blade open with a flick of your wrist. It works, but I tend to use too much force and the blade bounces back and partially closes before it can lock into place.
You can do it with a little practice, but personally, I’ll stick to the excellent flipper or thumb studs.
The handle of the SOG Pentagon XR is made from G10 and is very well done. It’s 4.77 inches long and extremely well textured. It’s that perfect mix of enough texture to ensure a firm grip, but not so much that it becomes uncomfortable in use or tears up your clothes.
A set of grooves at the butt of the handle and where your thumb lies help to further enhance your grip, especially in wet or slimy conditions.
A pronounced index finger groove melds with the flipper when the blade is open to create yet more point of positive contact on the handle and to prevent your hand from sliding up onto the blade during hard thrusts or stabs.
The handle has an open back too to keep crud from collecting in the mechanism and to make the knife easy to clean. My test model was basic black, which never goes out of style, but OG Green, Flat Dark Earth, and carbon fiber handles are also available.
The SOG Pentagon XR is fitted with a discrete low profile reversible pocket clip set up for left- or right-hand, tip-up carry. It’s a good clip with the proper mix of enough tension to hold the knife in place, but not so much that it’s hard to put in your pocket or draw the knife. It’s also not rough on your pocket edges either. The skeletonized clip cuts down on the profile as well.
The Pentagon XR is part of SOG’s professional series and designed for defense, but it makes a great utility blade as well. It carries easily in the pocket, and although it feels solid in the hand at its 4.9-ounce weight, it is still light and trim enough that in the pocket you don’t really notice it.
I’m always picky about tip-up blades because I’ve had a number of them over the years slip open enough to either catch and cut clothing or stab me in the hand when I go to draw the knife.
There are no such issues with the Pentagon though. It stays shut as it should when closed but opens fast as you draw it.
“The keen tip punched through leather and denim with ease, and I could sink the blade to the hilt in my stacked cardboard test target…”
If you’re a fan of the sharpened pry bar, then the Pentagon is probably not for you. It’s only 0.118 inch thick and with its double grind has a fairly thin profile. That makes it a great slicer and stabber though.
The keen tip punched through leather and denim with ease, and I could sink the blade to the hilt in my stacked cardboard test target using an overhand, ice pick grip.
It doesn’t have a lot of belly for slashing, so I wasn’t expecting much, but the dagger-shaped tip still made wicked cuts that raked much deeper into my test target than I expected.
Underhand thrusts penetrated deeply as well—basically what you’d expect from a dagger pattern, even without the unsharpened back edge. The excellently shaped and textured grip kept my hand in place during the slashes and especially stabs too. I never felt in danger of having my hand sliding up onto the blade even with full-power stabs.
Even if you don’t expect to find yourself in a lot of knife fights, the Pentagon XR is an excellent EDC knife. It carries and handles well, is made from top notch materials, and comes ready to roll from the factory. It can easily handle utility chores as well as it does defense ones too.
The Pentagon XR would actually work great as a field knife too. In fact, even though it’s not designed to be one, that handle shape and spear-point blade, combined with the thin edge, remind me a lot of a bushcraft blade.
Whether you have a specific purpose in mind, or just need a quality folder that fill multiple roles, I’d recommend giving the Pentagon XR a hard look. My tester has become one of my favorite EDC knives and I plan on grabbing a second one in OD Green soon.
CARPENTER CTS XHP STEEL
I’ll be the first to admit that I’m a basic steel kind of guy. I don’t mind good old 1095 high carbon, Bucks 420HC, or Sandvik 12c27. As long as it has a good heat treat, I can work with it. I don’t even mind taking care of carbon steel or dealing with some patina from use if I don’t get to it quick enough with some oil.
And I try to keep my blades stropped so I don’t have to resharpen them as often. With that said, I get the allure of a blade that doesn’t need as much maintenance and doesn’t need sharpened nearly as often, and I know a lot of consumers demand it.
Carpenter Technology has been around for over 130 years and the company knows a thing or two about steel. Its powder metal CTS XHP stainless steel that’s used in the Pentagon XR has excellent corrosion resistance properties and well as edge retention. It can be hardened to a 64 Rockwell and has been described as either a high hardness 440C or a corrosion resistant D2 tool steel.
That combination of features makes it perfect for a hard use blade. I don’t have months of carry in with my Pentagon XR yet, but I did do a lot of cardboard cutting and stabbing, and some work on sisal rope, which usually takes its toll on a blades edge.
So far, I can’t tell of any edge degradation, and there is definitely no chipping, or deformation present. This is my first run in with CTS XHP, but so far I’m impressed and I’m looking forward to seeing how it holds up in the months and years to come.
SOG Pentagon XR
Blade Length: 3.61 inches
Closed Length: 4.77 inches
Overall Length: 8.38 inches
Blade Material: CTS-XHP stainless steel
Thickness of Blade: 0.118 inch
Blade Style: Spear point
Finish of Blade: Black titanium nitride
Handle Material: Black G10 (OD, FDE and carbon fiber available)
Locking Mechanism: XR
Pocket Clip: Tip up deep carry, right/left hand
Weight: 4.9 ounces
Made in Taiwan
6521 212th Street Southwest
Lynnwood, WA 98036
Editor’s note: A version of this article first appeared in the May / June 2021 print issue of Knives Illustrated.