Spyderco Fine Grit Slip Stone Sharpener (Review) 2021

This sharpener is durable, versatile, and portable.

By Josiah Johnston | Updated Oct 28, 2021 9:08 AM EDT

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Spyderco has been one of the biggest names in the knife industry for decades, producing their first folding knife model in 1981, which debuted their now-infamous Round Hole™ opening system and the pocket clip. The Round Hole™, colloquially referred to as the Spydie-hole, allows for easy, ambidextrous one-handed opening, while having a larger surface area than thumb studs, thumb disks, or nail nicks, and remaining easily accessible, even while wearing gloves. Their innovative pocket clip went on to inspire their CLIP-IT® line, and soon became accepted and implemented by most pocket knife companies.

Based out of Golden, Colorado, Spyderco has an extensive catalog, offering both exclusive and limited runs of their more popular models in various boutique blade steels, handle materials, and colors. Its founder, Sal Glesser, was inducted into Blade magazine's Cutlery Hall of Fame in 2000, and they have arguably experimented with more new blade steels than any other pocket knife manufacturer. However, their origins actually lie in sharpening systems and tools. Their first knife sharpeners debuted in 1978, with their most popular sharpening system being the Spyderco Tri-Angle Sharpmaker. They have many other sharpening products available, including sharpening stones in various styles and grit levels, one of which is the Spyderco Slip Stone.

The Spyderco Slip Stone is a bit of an oddity as far as sharpening stones go. Whereas most stones are flat and rectangular, a slip stone has rounded edges, resulting in a teardrop shape when viewed from the side. This allows the stone to maintain the edge on a larger variety of blade shapes, as normal stones struggle to sharpen recurve blade styles like the karambit or the khukri. The Spyderco Slip Stone is a relatively inexpensive ceramic stone, coming in at less than $90.

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Spyderco has never been one to splurge on packaging, and this product is no exception. The Slip Stone comes in trapped blister packaging, similar to what you’d find hanging on the shelves of many retail stores. The front of the cardboard is in Spyderco's normal packaging colors of red, white, and black, with ‘SLIPSTONE’ written at the bottom, ‘Spyderco’ at the top, and the Spyderco emblem underneath that in gold. The backside of the package reveals a black background with white lettering. It covers everything from information on Spyderco's extensive line of ceramic sharpening tools, cleaning/maintenance, and warranty/liability information, to Spyderco's contact information at the very bottom.

The Slip Stone itself is showcased inside of the clear plastic, with the brown suede leather pouch behind it. After freeing it from its plastic prison with my QSP Penguin, my initial impressions were somewhat cliche: It's smaller than I expected. The stone is just slightly over four inches long, about two inches wide, and is half an inch at its thickest point. It fits comfortably in the palm of my hand and weighs around seven ounces with the pouch, which makes it a good potential option for field maintenance. It's manufactured out of white American-made high alumina ceramic, and is advertised by Spyderco as being a fine grit stone (compared to Spyderco's medium grit stones, which are brown), and feels like it's just over 1,000 grit. The larger convexed side is perfect for recurved blade styles, while the smaller recurved side is designed for larger serrations. The two remaining sides are terminated at a 90-degree angle like on a traditional stone, allowing you to sharpen straight or traditionally curved edges.

The brown leather slip, or pouch, that the stone comes with is three inches wide, and just over five inches long. It's made from suede with white stitching, and while plain, seems to be well-constructed. It features the Spyderco emblem on the front, with the words ‘Spyderco, Inc.’ in large font, and in smaller letters under that, ‘Golden, Colorado, USA’. It's advertised as a carry pouch, but also as a slip-resistant base for the stone, should you prefer table sharpening over holding the stone in your hand. You can also use it as a strop in a pinch, though it's a lot smaller than what I’d personally use.

For testing, I did exactly what one would expect to do with a sharpening stone: I sharpened. As a mild disclaimer, I am not a professional knife sharpener, and have primarily used fixture sharpening systems made by Lansky and Smith, along with some experience using a Tormek T8.

I started off by procuring three kitchen knives in various degrees of disrepair. The first one I sharpened was a 5.75-inch long sheepsfoot-style blade that I had previously sharpened. There wasn't any major edge damage in the form of microchipping (small chips or nicks in the edge) or rolling (where the edge literally bends over), but the edge was dull from use. As I was just doing a touch-up, I had the edge apexed in less than five minutes, and stropped the burr off with my handmade strop (a random scrap of leather I found in my garage four years ago) using Marbles green honing compound. The green honing compound is between 5,000 and 6,000 grit, which creates a near-mirror finish on most blade steels.

The second kitchen knife was a paring knife with a 3.5-inch long blade that still had the factory edge. It had seen a similar amount of use as the first knife and didn't have any major edge deformation, but it required more work due to the factory edge being somewhere around 200 grit, and the factory edge terminating around two centimeters before the ricasso where it should have ended. In addition, sharpening freehand results in a slightly convexed edge (compared to the flat edge you get with machines or fixture sharpening systems like the Lansky, Worksharp, KME, or Wicked Edge systems), so reprofiling the flat factory edge to a convex edge took a little longer. After an hour of reprofiling, apexing, and extending the edge back to the ricasso, I stropped the burr off and was left with a near-mirror edge.

The third kitchen knife was a mistake to attempt on my part. It had been ‘sharpened’ extensively with a pull-through style sharpener, which is known for removing too much blade material, creating recurves in the edge, and leaving you with a very poor quality edge. The eight-inch-long blade featured a pit in the edge around two inches in from the tip, a recurve in the edge around one inch from the ricasso, and a ricasso that needed reduced due to how much steel had been removed previously. The edge was completely dull as well, with more than a few microchips.

I started off by filing down the ricasso to just slightly below the level of the edge, using a diamond file. Ideally, you’d want to make the ricasso even with the edge to make food prep on a cutting board easier, but I knew that I was going to have to remove a lot of material from the edge, so I overcompensated. I then spent the weekend attempting to reprofile the edge, unsuccessfully, during which I discovered a second recurved area near the middle of the blade, and that the pitting in the edge was much deeper than it initially appeared. I spent a few more days attempting to fix the edge with just the slip stone, but eventually, I gave in and reprofiled the edge with a 70 grit Lansky stone. After doing this, I was able to achieve a similar result to the first two knives, though I wasn't able to completely remove the pitting.

The last thing I did was to attempt to sharpen my Cold Steel Frenzy, which had a dull tip from an overzealous Marine who used it to cut a pineapple on a concrete bench. As expected, the CTS XHP steel used for the blade was too hard for me to be able to completely reprofile it on a fine stone, so I gave up after an hour or so.

The stone cleaned up very easily; my hand quickly wiped off most of the steel residue, and what little my hand didn't remove came off easily with water and dish detergent. Spyderco advises cleaning the stone with freshwater, powdered abrasive cleaner, and a scouring pad, and then leaving the stone out to air dry.

The Spyderco slip stone is exactly what it claims to be: a fine-grit ceramic slip stone. It's lightweight and small enough to be easily portable and packable, should you choose it for field use. It's easy to sharpen with the stone by holding it in your hand, which can be helpful when you don't have a table or similarly stable surface available. In some ways, it's actually easier to use it while holding it in your hand, though your experience may vary. I was able to easily achieve a near-mirror finish after stropping thanks to the fine grit stone leaving a very minimalistic scratch pattern, and I had no issues with the stone chipping, dishing out in the middle, or getting any sort of noticeable, appreciable wear. The fact that ceramic doesn't require lubricant means that you’ll make much less of a mess with this stone compared to stones that require oil or water, and it's also one less thing you have to worry about bringing with you if you plan to use this in the field.

The brown, suede leather slip that came with the stone proved surprisingly helpful, as I sharpened in quite a few different locations over the course of this article. It also worked well to keep the stone from slipping around when I tested sharpening with it stabilized on my workbench. All in all, this is a quality product that seems to have reinvested what money may have been saved on packaging to the end-user.

The only real issue I found with this product was the flats of the slip stone — or, rather, the attempt. The flat sides of the stone where you’d do most of the sharpening of straight or traditionally curved blades was slightly lower than the radiused sides, resulting in it being slightly recurved. This didn't pose a huge issue, as I simply rotated the stone 90 degrees to a side that wasn't radiused and kept sharpening, but it was slightly disappointing. I’m not sure if it was intentionally part of the design or a lapse in quality control, but I can't think of any reason why it would be an intentional choice. It is worth noting that while ceramic stones are extremely wear-resistant and aren't likely to dish out, they can break if dropped due to how hard ceramic is, similar to what would happen if you dropped a ceramic coffee mug.

My only other complaint actually has nothing to do with the Spyderco slip stone, but rather has everything to do with Spyderco: They don't offer a medium grit slip stone. This causes the issue I ran into when attempting to sharpen the third and fourth knives, as you need a medium- or low-grit stone to reprofile most knives that have major edge damage or are made from high-end or premium steels. While it's possible to attach adhesive lapping film or sandpaper to the slip stone, Spyderco should offer either a medium-grit ceramic or diamond slip stone.

Whether you’re fixing up your wood chisels, honing your tactical karambit to a razor edge, or just trying to bring your camp knife back to a functional edge, the Spyderco Slip Stone has you covered. Between the portable nature of the stone and the absence of a need for messy lubricants, you can take and use this almost anywhere, and the impressive wear resistance practically guarantees you decades of sharpening.

More questions? Here's Task & Purpose's additional brief.

A. Spyderco's MSRP is $86, but it can frequently be found for around $60 through most knife retailers or on Amazon.

A. High alumina ceramic is made from a process where alumina particles, synthetic sapphires, are combined with a bonding agent to form a stone, which is then placed in a kiln and baked to 3,000 degrees Fahrenheit. Stones made from this process come in at around nine out of 10 on the Mohs hardness scale, placing them just under diamonds, and as a result rarely wear out or need to be replaced. As an added benefit, lubricants such as water or oil aren't necessary for use.

A. Arguably one of the most important steps in sharpening, stropping is definitely one of the more neglected steps in sharpening, and is most commonly remembered for its usage by barbers with straight razors. A strop is typically made from a flexible piece of leather, canvas, or balsa wood, and is used to straighten or break off the burr formed on the apex of the edge when sharpening, leaving a hair-shaving edge. Strops are frequently coated in polishing or honing compounds, which help reduce or remove imperfections in the edge, while also reducing the friction and drag experienced when cutting through various materials. Stropping can be done as part of routine maintenance as well, as it can help realign areas of the edge that have rolled or bent over. Additionally, stropping can remove a miniscule amount of metal when combined with an abrasive honing compound.

A. A ricasso is the unsharpened area of a blade, right between where the primary grind ends and the handle begins. There are a few reasons for the existence of a ricasso: It can be a purely aesthetic choice, reinforcement at a high-stress area in the blade, a necessary feature for a locking mechanism in folders, or a feature that allows you to grip higher on the blade for increased control and torque.

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Josiah Johnston is an active duty Marine stationed at Camp Pendleton, originally from the Eastern Panhandle of West Virginia. He's dabbled in blacksmithing, martial arts, competitive shooting, and is a self-described knife nerd.

Josiah Johnston is an active duty Marine stationed at Camp Pendleton, originally from the Eastern Panhandle of West Virginia. He's dabbled in blacksmithing, martial arts, and competitive shooting, and is a self-described knife nerd.