The Work Sharp Professional Precision Adjust sharpener has gained a following among knife enthusiasts for its guided system that takes much of the guesswork out of sharpening. But the base kit only gets you so far. The 320 and 400 grit coarse diamond abrasive kit is an optional add-on that expands the system’s capabilities, particularly for those who need to repair damaged edges or reset bevels. This review examines what the kit offers, how it performs in practice, and where it might fall short for some users.
The kit includes two diamond stones: a 320 grit and a 400 grit. Both are mounted on plastic carriers that slide into the Precision Adjust’s guide rod. The stones are color-coded (320 is black, 400 is red) for easy identification. Diamond abrasives are known for their longevity and ability to cut hard steels, including high-vanadium alloys that can frustrate traditional stones. The 320 grit is the more aggressive of the two, intended for heavy material removal, while the 400 grit serves as a bridge between coarse and medium grits.
In real-world use, these stones are most valuable when a knife has sustained damage—chips, rolls, or a completely dull edge that needs reprofiling. For routine touch-ups, they’re overkill; the finer stones in the base kit (600 and 800 grit) are better suited. But when you need to remove a lot of metal quickly, the 320 grit makes short work of it. The 400 grit follows up to refine the scratch pattern before moving to finer grits. Users who sharpen frequently or work with older knives will appreciate having these coarser options on hand.
One of the key advantages of diamond stones is that they stay flat and cut consistently. Unlike water stones, they don’t require soaking or flattening. The trade-off is that they can feel harsh and leave deeper scratches if not used carefully. Also, diamond stones can be aggressive on softer steels, removing material faster than expected. It’s easy to overshoot and create a larger bevel than intended, especially on thin kitchen knives. The 320 grit, in particular, demands a light touch and frequent checking of progress.
Compared to other guided sharpening systems like the KME or Edge Pro, the Work Sharp Precision Adjust is more affordable and portable, but its stone options are more limited. The coarse diamond kit helps close that gap, but it’s not as comprehensive as the stone selections available for those systems. For example, Edge Pro offers a wider range of grits and stone types, including diamond matrix stones that some users prefer for their feedback. However, the Work Sharp system’s clamp-based design is quicker to set up and works well for most folding knives and smaller fixed blades.
Who is this kit for? It’s aimed at owners of the Precision Adjust who regularly sharpen knives and need to do more than just maintenance. If you often buy used knives, repair edges for friends, or just want to be able to handle any sharpening task, the coarse diamond kit is a worthwhile addition. It’s also useful for those who sharpen harder steels, as diamond abrasives handle them more effectively than the included aluminum oxide stones. On the other hand, if you only sharpen your own knives occasionally and they never get seriously dull, you might not need this kit. The base kit’s 600 and 800 grit stones are sufficient for maintaining an already sharp edge. Also, if you’re new to sharpening, starting with such coarse stones can be risky—it’s easy to remove too much metal and shorten the life of your knife.
In terms of build quality, the stones are well-made and fit securely in the guide rod. The plastic carriers are durable enough for repeated use, though they can develop a little play over time. The diamond surface is evenly distributed and shows no signs of premature wear after several sharpening sessions. As with any diamond stone, they should be used with water or oil to prevent clogging and reduce heat buildup, though the manufacturer doesn’t specify a preference. A few drops of water work fine.
One limitation is that the 320 and 400 grits are close in aggressiveness, so the jump between them isn’t huge. Some users might wonder if they need both. In practice, the 400 grit does leave a noticeably finer scratch pattern, but the difference is subtle. If you’re on a budget, you could probably get by with just the 320 grit and then move to the 600 grit. However, having both allows for a more gradual progression, which can lead to better results with less risk of deep scratches that are hard to remove.
Another consideration is that these stones are specifically designed for the Precision Adjust system. They won’t work with other sharpeners unless you have an adapter. That’s expected, but it means you’re locked into the Work Sharp ecosystem for coarse grit options. Fortunately, the system itself is popular enough that third-party stones are starting to appear, but they vary in quality.
Overall, the Work Sharp Professional Precision Adjust 320 & 400 Grit Coarse Diamond Abrasive Kit is a practical addition for anyone who needs to do serious sharpening work with the Precision Adjust. It’s not a mandatory purchase for every user, but for those who sharpen often or deal with damaged edges, it fills an important gap. The diamond stones cut fast and last long, but they require a careful hand to avoid over-grinding. If you’re comfortable with the sharpening process and want to expand your capabilities, this kit is worth considering. If you’re just starting out, you might want to master the finer grits first before adding these aggressive stones to your setup.
