Ultra Sharp Diamond Sharpening Stone Set: problems, parts and running costs

Checked: 2026-10-19

Summary

The set is three 8 x 3 in monocrystalline-diamond plates (300/600/1200 grits) with an adjustable holder, and the two things to check before buying are quality control and the warranty: a 2024 review found grit contamination and raised plating spots on the finer grits, and the retailer advertises a lifetime guarantee while its written policy allows 30 days. Running costs are just lubricant — about $8 per quart for Krud Kutter, or near zero with plain water. It is a strong buy at the $61-80 street prices observed at Home Depot and a poor one at the $166.74 manufacturer MSRP.

Common problems and fixes

Grit contamination and plating clumps on finer grits — a 2024 review of a $60 Ultra Sharp set found raised plating spots on the 600 grit that scratched bevels and clumps plus grit contamination on the 1200 grit; the review likely covered the smaller 6 x 2 in variant, so the findings may not transfer to this 8 x 3 set. Rinse stones periodically to remove loose diamond particles and clean with Krud Kutter and a nylon brush; the review author moved to Sharp B stones and a Koraku stone instead. Warranty coverage is contested (see below). [10][1]
Warranty conflict — Best Sharpening Stones advertises a “Lifetime Guarantee” on its product and category pages, but its own guarantee page accepts returns only within 30 days, unused, in original packaging, with buyer-paid return shipping; the manufacturer states only “No Questions Asked 100% Guarantee” with no duration. Treat the written 30-day terms as the enforceable baseline and get the terms in writing before buying. [2][3][1]
New stones need a break-in — the manufacturer requires breaking in new stones before use and warns against flattening chisel or plane-blade backs with a brand-new stone; seller listings do not mention this. [1]
No coarse grit below 300 — 300 is the coarsest stone in this line, so heavy reprofiling or chip repair is limited; a BladeForums member flagged this when recommending a Norton stone instead. [13]
Rust discoloration — remove with Bar Keepers Friend and dry the stones before storage, per the manufacturer’s maintenance guidance. [1]

Parts and consumables

Replacement stone, 8 x 3 in, single grit — $42.95-$48.95 each at Best Sharpening Stones (2026-10) and $56.34-$58.74 each from the manufacturer; how often owners replace them is not reported. [4][1]
Adjustable stone holder — $17.95 at Best Sharpening Stones (2026-10), or a $19 add-on on the manufacturer’s site; included with this set. [4][1]
Krud Kutter lubricant — about $8 per quart at Lowe’s and Home Depot (2026-10); plain water or glass cleaner also work, and owners report using mineral oil or mineral spirits. No lubricant is included. [1][5][12]

Yearly running cost

Hand stones with no power source, so the only recurring cost is lubricant: about $8 per quart for Krud Kutter at Lowe’s and Home Depot (2026-10), or near zero with plain water, which the manufacturer says also works. No other consumables, parts or service charges are reported; how long a quart lasts is not documented. [1]

When it is a good buy

Home Depot listing mirror: $61 for the 300/600/1200 8 x 3 set with holder; a second snapshot showed $80 for the same described set. [15][16]
Best Sharpening Stones (the manufacturer’s own retail destination): $116.95 without holder, $128.95 with holder. [2]
Manufacturer MSRP: $166.74 with holder; $143.94 for the same three stones without it. [1]
Walmart aggregator mirror: $44 for the 2-stone 600/1200 variant — a different model, listed only as a brand price anchor. [17]

At $61-80 the set undercuts the MSRP by more than half and competes directly with DMT Dia-Sharp kits that cost more per stone. At $116.95-128.95 it is fair if the 8 x 3 in size matters. At the $166.74 MSRP it is overpriced against every observed street price for the identical set. Named alternatives: DMT Dia-Sharp stones, the benchmark several owners compare against; Sharp B stones (about $70 for a 3 x 8 in 325/1200 stone) and a Koraku stone, the 2024 review author’s picks; and Atoma plates, which a Reddit owner with several Atoma plates called inferior to the Ultra Sharps after about a year. [11][13][10][5]