# Knives, shears and cutting tools: research notes

Date: 2026-10-25. Scope: kitchen knives sold singly (chef's knife or gyuto, santoku, paring, bread, utility or petty, boning, slicing, cleaver or nakiri, steak knives), knife block sets, kitchen shears, and the tools that keep knife edges (whetstones, pull-through and electric sharpeners, guided systems, honing rods). Not covered: cutting boards (sibling `kitchen-boards`), peelers, corers and zesters (sibling `graters`), cookie and biscuit cutters (sibling `molds`), electric meat slicers (machines / appliances / grinders), craft scissors (supplies / crafts / cutting_tools). Mandolines, pizza wheels and egg slicers can land in this leaf, but they sit closer to the graters sibling and no source read for this run covers them; the register gives them no facets and the `tool_type` split has no value for them (see Judgements).

Taxonomy path: `supplies > kitchen > knives`. The JSON uses `"vertical": "other"` because the skill's `schema.json` enum (formulations, machines, fashion, furnishing, other) has no `supplies`; `validate.py` rejects `"supplies"` (checked against the sibling `labels/category.json`, which fails for exactly that reason). Reported as a script problem.

Quote labels: **verbatim** = the sentence in quotation marks was in raw text I read myself (curl plus HTML stripping, or pdftotext on a downloaded PDF); **fetched excerpt** = the WebFetch tool summarised or reworded the page; **search excerpt** = the claim came from a search-engine summary only. No search-excerpt-only number is in category.json.

Fetch notes: Serious Eats (people.inc) returns an access-denied page to curl, so every Serious Eats page was read from an Internet Archive snapshot (URLs below carry the snapshot timestamp). Amazon product pages returned full HTML to curl for every ASIN tried; Amazon search pages did not. The session's web-search budget ran out part-way through research (200 of 200, shared with parallel runs), so later sources were reached by following links inside pages already fetched.

## Seed

Seed output (verbatim from `seed.py --category knives`):

- Example: car-tyres `treadwear_grade`: "a number that is on every listing and still needs a judgement attached, because experts know it only compares within one manufacturer's range."
- Persona: "A competitive endurance athlete, who thinks in cost per unit of the active thing and what is a waste of weight"

1. **The knives equivalent of treadwear is the Rockwell hardness (HRC) number.** It is the one spec number brands print, it is real (a defined indentation test), and it still needs a judgement: it says how hard the steel is, not how long the edge lasts. Knife Steel Nerds' CATRA work finds edge retention set by hardness, carbide volume and type, and edge angle together, and says sharpening angle and grit "have a greater effect on performance than steel choice" (verbatim). The Quantified Knife Project's 16 chef's knives with a stated HRC show it: hardness correlates with measured edge retention at r = 0.53, edge angle at r = -0.63 (my arithmetic on their published figures, table below). Brand HRC is also a range or a claim, and measured edge angles miss the advertised ones by up to 4 degrees. **Kept** as `rockwell_hrc` (annotation) feeding `hardness_class` (split), with a judgement that HRC compares hardness, not edge life. A second treadwear analogue, the CATRA total card cut (TCC), survives as `catra_tcc`, researched and top-N only.
2. **The endurance athlete notices first that a block set is mostly dead weight.** The "pieces" count includes the block, the steel and the shears: the ZWILLING Gourmet 10-pc set lists 7 knives, a steel, shears and a block (Amazon Included Components, verbatim), three of them paring-type knives and two serrated (Serious Eats sets review, verbatim). Reviewers say three knives do almost all the work. **Kept** as `core_knives_included` and two derived metrics, `knives_in_set` and `cost_per_core_knife`. The athlete would also weigh the knife: German forged chef's knives weigh 230 to 272 g, Japanese-style 176 to 212 g, the stamped Victorinox 131 to 167 g. **Kept** as `blade_weight_g`, with the finding that weight does not track hardness (Victorinox is soft and the lightest). **Dropped**: "full tang and bolster are wasted weight". It is plausible and the add-on flags tang claims as a trap, but no source read for this run tests tang or bolster against performance; ATK's only bolster remark is that a large bolster shortened one knife's usable edge to 7.75 in. Vocabulary only.

## Sources and what each supports

### Standards bodies and test labs

**ISO 8442-5:2004, Specification for sharpness and edge retention test of cutlery (iTeh preview PDF, pdftotext)**
https://cdn.standards.iteh.ai/samples/30037/f0fe66a564194e379bfa0eeeb933bda5/ISO-8442-5-2004.pdf
- verbatim scope: "specifies the sharpness and edge retention of knives which are produced for professional and domestic use in the preparation of food of all kinds, specifically those knives intended for hand use."
- verbatim: "Type A edges: Cutting edges which can be resharpened by the user and edges with a pitch greater than 1 mm; Type B edges: Cutting edges which are not intended to be resharpened on a steel."
- verbatim definitions: ICP "cutting ability to be expected by the user from a knife when supplied 'as new'"; TCC "cumulative amount of card cut (measured in millimetres) by the test knife over the duration of a full test".
- verbatim Table 1: load 50 N, stroke 40 mm, 50 mm/s, 60 cycles for type A and 200 for type B.
- verbatim Table 2 "Performance levels": type A minimum ICP 50 mm, minimum CER (TCC) 150 mm; type B minimum ICP 50 mm, minimum CER (TCC) 1 500 mm.
- Supports: the CATRA test is the standard's method; the 50 mm and 150 mm floors. Confidence high.

**Lee Knives, How to test knife sharpness (maker page, curl)**
https://leeknives.com/knife-testing/
- verbatim: "According to ISO standards, a good sharpness level for a knife is around 50mm of paper cut."; "To be considered as having decent edge retention, a knife should achieve a minimum of 150 Total Card Cuts (TCC)."; bands "< 150 Poor", "150 – 280 Fair", "280 – 370 Good", "370 – 500 Great", "> 500 Excellent".
- Supports: second source for 50 mm and 150 mm. The bands are the maker's own, not the standard's. Confidence high for the two ISO numbers.

**Butterfork, CATRA testing (maker page, curl)**
https://butterfork.com/pages/catra-testing-sharpness-performance
- verbatim: "Chef's Knives When ICP > 110 mm and CER > 550 TCC mm, Sharpness Longevity is rated as Excellent."; bread knives "CER > 4000 TCC mm"; self-reported table, factory sharpened: ICP 104.9 / 106.4 / 118.8 / 127.7 / 139.0 / 129.4 / 132.0 and TCC 476.6 / 441.3 / 617.1 / 781.5 / 714.7 / 4660.1 / 731.2 for Wüsthof, three Globals, a Knife Gourmet and three Butterforks.
- Supports: makers set their own "excellent" bands (550 here, 500 at Lee Knives), and serrated knives post far larger TCC numbers. Not used for any number in the JSON, because these are maker-run tests of their own and competitors' knives.

**ISO 8442-1:1997, Requirements for cutlery for the preparation of food (iTeh preview PDF, pdftotext)**
https://cdn.standards.iteh.ai/samples/17759/a7bf4b09f3ed427f8b5da672aa161886/ISO-8442-1-1997.pdf
- verbatim scope: "specifies material and performance requirements and test methods for metal cutlery and related implements intended for use in the preparation of food."
- verbatim grades: "a normal grade with corrosion resistant blades or prongs capable of withstanding dishwasher cleaning procedures; a special grade with corrosion resistant blades capable of withstanding dishwasher cleaning procedures and sterilization processes."
- verbatim Table 1: knife blades with type "A" cutting edges, martensitic stainless steel (X39Cr13, 1.4031), "12,50 % min. Cr", "0,36 % min. C".
- verbatim 5.1: "The design of the cutlery shall be such that thorough cleaning processes can be readily carried out to avoid contamination of prepared foods."; 5.2.4 "There shall be no gaps in excess of 0,3 mm between components of the cutlery."
- verbatim 5.3: "Except where intended for chopping or boning, cutting edges shall be formed to an included angle no greater than 40 [degrees] and shall be no thicker than 0,46 mm when measured 1 mm from the extremity of the edge".
- verbatim introduction: the standard "does not cover those features of cutlery which are matters of choice for the user, such as the shape and size of knife or spatula blades"; "Attention is drawn to Directives of the European Community concerning materials and articles in contact with food".
- Supports: the food-contact and construction floor; 12.5% chromium for resharpenable blades; the 40 degree included-angle ceiling. Confidence high.

**IS 15104 (Part 1):2002, Indian Standard, identical adoption of ISO 8442-1:1997 (law.resource.org PDF, pdftotext)**
https://law.resource.org/pub/in/bis/S08/is.15104.1.2002.pdf
- verbatim Table 1: "12,50 % min. Cr" for type A knife blades; 5.3: "included angle no greater than 40~ and shall be no thicker than 0,46 mm".
- verbatim 6.4: "Knife blades with cutting edges shall have a hardness not less than 52 HRc for knives with type 'A' edges and not less than 48 HRc for knives with type 'B' edges when tested in accordance with 1S0 6508:1986."
- Supports: second copy of the 12.5% and 40 degree figures; the only text I read with the hardness clause. The 52 HRC floor is therefore single-document and stays in these notes, not the JSON. (A search summary gave the floor as "50 HRC"; the text says 52.)

**CATRA, Product testing services (curl)**
https://www.catra.org/testing-services/testing-product-evaluation/
- verbatim: "All types of food preparation and processing blades and knives are tested by CATRA to EN ISO 8442-1 and EN ISO 8442-5. The tests cover the following attributes and more: Blade sharpness, durability, geometry, strength and hardness Corrosion and dishwasher resistance"; "Knife Sharpener Testing Using EN ISO 8442-5"; "CATRA have developed in-house test protocols to assess sharpness and durability of all types of scissors and shears."
- Supports: ISO 8442-1 and -5 are the tests the trade's lab runs; shears have no ISO test. Confidence high.

### Specialist reviewers who measure

**Seattle Ultrasonics, Quantified Knife Project (QKP), individual knife pages (curl)**
Index pages: https://seattleultrasonics.com/pages/knife-pages/<slug>. Each page states material, "Edge Angle: X° measured (Y° advertised)", "Hardness", weight ("weighs N grams"), CATRA "First Cut Depth" and "Total Cardstock Cut", and a BESS score. Edge angles "directly measured ... using a CATRA laser goniometer" (fetched excerpt, How to Use the QKP page). The figures I read are in "Data points" below. Seven pages are cited in the JSON: wusthof-classic-8-chefs-knife, victorinox-swiss-classic-8-chefs-knife, shun-classic-hollowedge-8-chefs-knife, miyabi-kaizen-ii-8-chefs-knife, mac-professional-mth80-8-chefs-knife, henckels-classic-8-chefs-knife, misen-ultimate-8-chefs-knife.
- verbatim (Wüsthof page): "Edge Angle: 14.5° measured (14° advertised) Hardness: 58 HRC"; "weighs 269.5 grams"; "Total Cardstock Cut 365.9mm"; "This blade was middle-of-the-pack for edge retention in CATRA testing despite having a respectable BESS sharpness that ranked in the top 10."
- Supports: measured angles, hardness as stated, weights, independent TCC. Confidence high for what the pages state; the company sells an ultrasonic knife, which does not bear on the measurements of other brands. Note: the Victorinox Swiss Classic and Swiss Modern pages both state 131.35 g, which may be a copy error; Cutlery and More gives 165 g and ATK 5.9 oz (167 g) for the Fibrox Pro.

**Knife Steel Nerds (Larrin Thomas, PhD metallurgist), Testing the edge retention of 48 knife steels (curl)**
https://knifesteelnerds.com/2020/05/01/testing-the-edge-retention-of-48-knife-steels/
- verbatim: "an average difference of 15.8 mm paper cut per 1 Rc was found."
- verbatim regression: "TCC (mm) = -157 + 15.8*Hardness (Rc) – 17.8*EdgeAngle(°) + 11.2*CrC(%) + 14.6*CrVC(%) + 26.2*MC(%) + ..."
- verbatim: "steel is not even the greatest controlling factor for edge retention. After all, sharpening in terms of grit finish and edge angle have a greater effect on performance than steel choice."
- verbatim: "with higher toughness, the knives are better able to handle thin, low angle edges without chipping."
- Supports: hardness and edge angle both drive edge retention, angle at least as much per unit; geometry beats steel choice. Confidence high (lab data, one author; QKP's independent figures agree in direction).

**Knife Steel Nerds, Knife steels rated by a metallurgist (curl)**
https://knifesteelnerds.com/2021/10/19/knife-steels-rated-by-a-metallurgist-toughness-edge-retention-and-corrosion-resistance/
- verbatim: "Using 10 dps sharpening (20 degrees inclusive on the chart) leads to about 5x the edge retention of 25 dps."
- verbatim: "Toughness is a measure of how much resistance a steel has to fracturing. In the context of a knife this would be chipped edges or broken knives."
- verbatim: "D2 has enough chromium to be stainless (~12%) but its high carbon means that too much chromium carbide is formed to leave enough chromium for stainless levels of corrosion resistance."
- verbatim: lemon juice test on 440A, D2 and 1095: "There was significant sharpness loss with 1095, almost none with 440A, and D2 was in between."
- verbatim: "Heat treatment and edge geometry can mean more for kni[fe performance]" (summary section; text cut at the strip boundary).
- verbatim: the toughness versus edge retention chart is drawn on a log toughness scale: "When we plot toughness vs edge retention on a log scale instead we get a straight line".
- Supports: the toughness-versus-edge-retention grammar; corrosion depends on chromium in solution, not chromium on the label; carbon steel loses edge to acid. Confidence high.

**Serious Eats, The best chef's knives (Wayback 2026-01-28)**
http://web.archive.org/web/20260128170647/https://www.seriouseats.com/the-best-chefs-knives
- verbatim: "Western knives usually have a double-bevel edge, shaped like a V"; Japanese blades "many feature an asymmetric bevel ... or a single-bevel, where one side is angled and the other is flush. (You'll want to make sure you buy a right-or left-handed knife in this latter style.)"
- verbatim: Western stainless "is soft and forgiving. The blade edge rolls faster than a harder knife, but it can be honed back into shape with a few swipes on a rod."; "most of the Japanese knives I tested were pure stainless steel".
- verbatim: "The sweet spot in terms of weight was around seven to eight ounces"; the Messermeister "was nearly 10 ounces, the heaviest of the lot. It was difficult to control, and its thick blade wedged into carrots".
- verbatim: "A dishwasher is too hot and harsh, and can prematurely dull blades."
- Supports: bevel and handedness, honing soft edges, weight, dishwasher advice. Confidence high.

**Serious Eats, Western versus Japanese-style chef's knives (Wayback 2025-12-06)**
http://web.archive.org/web/20251206161117/https://www.seriouseats.com/western-versus-japanese-style-chefs-knives-6751328
- verbatim (quoting Josh Donald, Bernal Cutlery): "Western knives are typically tempered between 52 and 58 Rockwell hardness, while Japanese chef's knives are around 58 to 65 Rockwell"; "More carbon at a higher hardness means the blade will be more brittle, but it will also hold an edge longer and work at a finer polished edge."
- verbatim: "a rolled edge can be reset with a honing rod, something that won't work well with the more brittle, harder steel of a Japanese knife. When it comes time to touch up a Japanese blade, you'll n[eed] a whetstone."
- verbatim: Japanese knives "have historically featured single-beveled blades, meaning that they're angled only on one side and are therefore right- or left-handed."
- verbatim: "if you're unlikely to want to learn the art of sharpening on a whetstone, or if you want your chef's knife to tackle hardy ingredients without chipping, a Western-style chef's knife might be a good choice."
- verbatim: "many Japanese knife-makers go beyond traditional Japanese styles to sell a wide range of hybrid knives".
- Supports: the hardness bands, the hone-versus-whetstone rule behind split 2, single bevel as a Japanese trait. Confidence high (bands agree with the brand figures below).

**Serious Eats, Honing vs sharpening (Wayback 2025-09-02)**
http://web.archive.org/web/20250902003902/https://www.seriouseats.com/honing-vs-sharpening-7096318
- verbatim: "Honing doesn't remove any metal from the blade; instead, it realigns the existing edge"; sharpening removes metal, "twice a year is good for most home cooks".
- verbatim (quoting Cangshan Cutlery): "Harder steel (typically Japanese) has better edge retention but can be more brittle. These types of steel do not require as much honing but may need to be sharpened more often. Softer metals (such as German steel) do require m[ore honing]".
- Supports: honing versus sharpening vocabulary; second source for the hone-versus-stone rule. Confidence medium-high.

**Serious Eats, Carbon steel chef's knives (Wayback 2025-12-09)**
http://web.archive.org/web/20251209142126/https://www.seriouseats.com/why-buy-carbon-steel-knives-best-kitchen-tools
- verbatim: "There is no 'official' designation for how much carbon is required for a knife to be classified as high-carbon, but the label is generally applied to blades made with at least 0.6% carbon content by weight (up to 1.5% or so)."
- verbatim: "Stainless steel, on the other hand, has at least 10.5% chromium added in".
- verbatim: "About half of the knives I tested were non-stainless carbon steel, meaning they started picking up spots of stains when they were exposed to acidic tomatoes in the first cutting test."; patina "is a type of oxidation on the metal, but it's not destructive."
- verbatim: "it's impossible to generalize based solely on stainless or high-carbon categorizations."
- verbatim: the Zwilling Kanren "stood out for its comfortable balance and easy-to-maintain stainless cladding".
- Supports: carbon versus stainless; "high carbon" is not a defined grade; clad blades. The 0.6% figure is single-source and stays here. Confidence high.

**Serious Eats, The best knife sets (Wayback 2025-09-02)**
http://web.archive.org/web/20250902004425/https://www.seriouseats.com/best-knife-set-7110371
- verbatim: "At the very least, a good set should include a chef's knife, a serrated knife, and a paring knife."; "The sets I tested for this review ranged from three pieces to 15."; the "Zwilling Gourmet 10-pc Knife Block Set ... comes with three kinds of paring knives as well as two serrated knives."; "A smaller set with thoughtfully chosen, well-performing pieces can easily outshine a bloated block filled with duplicates or knives you never touch."
- Supports: the core three; sets carry duplicates. Confidence high.

**Serious Eats, The best knife sharpeners, including whetstones (Wayback 2025-09-02)**
http://web.archive.org/web/20250902003954/https://www.seriouseats.com/best-knife-sharpeners
- verbatim: whetstone "A minimal amount of the knife's edge is removed—even on coarser stones—so this is ultimately the best for your knife's longevity."; "electric sharpeners tend to grind away more of the knife's edge than whetstones, they have a lower risk than pull-through sharpeners of scratching and nicking the knife."; pull-through "is prone to damaging knives. I don't recommend using a pull-through sharpener for your favorite knives."
- verbatim: "It's best to buy a whetstone with a 1,000 grit stone (a baseline minimum) and a fine grit stone of 5,000-6,000 (for giving the knife a fine finish)"; "you should start with 800 or 1,000 grit (anything lower is for repairing the blade)".
- verbatim: "you want to situate your blade at a 15- to 20-degree angle."
- Supports: sharpener types ranked by metal removed; the grit ladder. Confidence high.

**America's Test Kitchen (ATK), The three knives every cook should have (curl)**
https://americastestkitchen.com/articles/8204-three-essential-knives
- verbatim: "Most cooks only need three knives."; essentials are a chef's knife, a paring knife and a serrated bread knife; "Made from hard Japanese steel, gyuto are more likely to chip and get damaged if used to break down chickens or cut denser foods such as butternut squash."; paring "blades measuring less than 4 inches".
- Supports: the core three; hard steel chips. Confidence high.

**ATK, How to build the best knife set (curl)**
https://www.americastestkitchen.com/articles/420-how-to-build-the-best-knife-set
- verbatim: block sets "are often filled with several knives you won't ever use in your home kitchen. We believe there are only three knives you truly need: a chef's knife, a paring knife, and a serrated bread knife."
- Supports: second ATK statement of the core three. Confidence high.

**ATK, The best chef's knives under $75 (curl)**
https://www.americastestkitchen.com/equipment_reviews/2357-the-best-chef-s-knives-under-75
- verbatim: "we focused on knives with blades measuring about 8 inches, as we've found this length to be the most useful and versatile for most cooks."
- verbatim: "Most of the knives we tested had narrow edge angles of 13 to 16 degrees"; sharpness "came down to a second factor: how well they had been sharpened and honed at the factory."
- verbatim: "Blades with thick spines ... have more power; while they sometimes wedge into food and get stuck, they are good at getting through dense butternut squash and bone."; weight: "Ultimately, the choice is personal".
- verbatim: Victorinox Fibrox Pro "Weight : 5.9 oz Edge Angle : 15°", "over the decades, it's proved itself to be a steady, stalwart companion"; Wüsthof Classic "heavy weight, thick spine, and big bolster"; one knife's "large, thick bolster ... limits the usable length of the knife to 7.75 inches".
- verbatim: "Can I put my chef's knife in the dishwasher? Please don't."
- Supports: 8 in default, factory angles 13 to 16 degrees, spine thickness trade-off, the stamped Victorinox as the long-running winner. Confidence high.

**ATK, The best manual knife sharpeners (curl)**
https://www.americastestkitchen.com/cooksillustrated/equipment_reviews/1608-the-best-manual-knife-sharpeners
- verbatim: "All sharpeners are designed to work with knives of specific edge angles. Traditionally, European knife manufacturers sharpened to 20 degrees and Japanese knife makers to 15 degrees (or less). But over the past decade or so, European knives have trended toward narrower edge angles too."
- verbatim: "In general, an older (10 years or more) kitchen blade from a Western manufacturer is likely to have a 20-degree edge angle; newer knives and Japanese knives are more likely to have narrower 15-degree angles."
- verbatim: "It's best to keep your knife at the edge angle it was designed to hold. ... So if you change a knife's angle from 20 degrees to 15, it'll need more frequent sharpening and you'll end up removing a considerable amount of metal from it over time."
- verbatim: "Compared to electric models, manual sharpeners are slower and can't repair deep damage such as chips in the blade."; pull-through, controlled-angle and other manual types described.
- Supports: the age-and-origin rule behind `sharpener_angle`'s question; converting angles costs metal. Confidence high.

**ATK, The best kitchen shears (curl)**
https://www.americastestkitchen.com/equipment_reviews/1877-kitchen-shears
- verbatim: "Take-Apart Design: We strongly preferred shears that could be easily separated for easy cleaning. Take-apart models allowed users to get rid of any chicken or herb bits that got stuck at the pivot"; "no take-apart models accidentally separated during use".
- verbatim: "all but one of the models in our lineup were ambidextrous".
- verbatim: "Cutterblades with thicker edge angles (more than 30 degrees) tended to wedge themselves into the food"; serrations "had to be on the edge of the blade or at least on the bevel".
- verbatim: shears "are critical for removing the backbone of the chicken—a task that can be really tough on your chef's knife."
- verbatim spec lines: Shun DM7300 "Can be taken apart : Yes Cutter blade angle : 25°"; J.A. Henckels 11517-100 "Can be taken apart : Yes Cutter blade angle : 50°".
- Supports: take-apart as the shears facet; ambidextrous is near-universal. The 30 degree wedge line is single-source and stays here. Confidence high for the take-apart preference.

**Wirecutter Show podcast, The only 3 knives you actually need (Apple Podcasts episode page, curl)**
https://podcasts.apple.com/us/podcast/the-only-3-knives-you-actually-need-in-your-kitchen/id1762217793?i=1000761497974
- verbatim: "Why you only need three knives: A chef's knife, a paring knife, and a serrated (bread) knife will handle nearly everything in a home kitchen. Most knife sets just add unnecessary 'filler' pieces."
- Supports: third source for the core three and set filler. Confidence high.

### Brand spec sheets (via Cutlery and More spec tables, brand pages and Chef'sChoice)

Cutlery and More (specialist retailer) prints the brand's spec block in the same order on every page: blade construction, handle, Rockwell hardness, edge angle, blade length, height, spine thickness, weight. All read with curl.
- Wüsthof Classic 8 in, https://cutleryandmore.com/products/wusthof-classic-chefs-knife-601 — verbatim: "Fully forged German stainless steel (X50 CrMoV 15)", "Rockwell Hardness: 58 degrees", "Edge: Approximately 14 degrees, double bevel", "Spine Thickness: 3mm", "Weight: 9.3 oz. (265g)".
- Zwilling Pro 8 in, https://cutleryandmore.com/products/zwilling-pro-chefs-knife-25203 — verbatim: "Rockwell Hardness: 57 degrees", "Edge: Approximately 15 degrees, double bevel", "Weight: 9.3 oz. (266g)".
- Shun Classic 8 in, https://cutleryandmore.com/products/shun-classic-chefs-knife-5286 — verbatim: "34-layer stainless steel Damascus with VG-MAX core", "Rockwell Hardness: 60-61 degrees", "Edge: Approximately 16 degrees, double bevel", "Weight: 7.5 oz. (212g)".
- Global G-2 8 in, https://cutleryandmore.com/products/global-chefs-knife-1073 — verbatim: "Cromova 18 high carbon stainless steel", "Rockwell Hardness: 56 to 58 degrees", "Edge: 10 to 15 degrees, double bevel", "Weight: 6 oz. (170g)".
- Victorinox Fibrox Pro 8 in, https://cutleryandmore.com/products/victorinox-fibrox-chefs-knife-42192 — verbatim: "Rockwell Hardness: 56 degrees", "Edge: Approximately 15 degrees, double bevel", "Weight: 5.8 oz. (165g)".
- Mac Chef series BK-80, https://cutleryandmore.com/products/mac-chef-series-chefs-knife-8094 — verbatim: "Rockwell Hardness: 60 degrees", "Edge: 15 degrees, double bevel", "Weight: 6.9 oz. (196g)".
- Victorinox brand page, Fibrox Pro 5.2063.20, https://www.victorinox.com/en-US/Products/Cutlery/Chef%27s-Knives/Fibrox-Pro-Chef%27s-Knife/p/5.2063.20 — verbatim fields: "Weight: 6.4 oz", "Forged: No", "Type of edge: Straight edge", "Length of blade: 7.9 in", "Dishwasher safe: Yes". No hardness and no edge angle on the brand's own page.
- Chef'sChoice 1520, https://chefschoice.com/products/chefschoice-diamond-hone-angleselect-sharpener-model-1520-white — verbatim: "Applies a traditional 20 degree edge or a finer 15 degree edge for precision slicing"; the page's own product tags (verbatim in the page source): "Traditional European & American style (20 degree edges)", "Asian and/or Contemporary European & American style (15 degree edges)". The 15XV model text (store products feed, same site): "upgrades traditional 20° factory edges into sharper 15° edges".
- What the brand fields tell us: hardness and edge angle are published by Wüsthof, Zwilling, Shun, Global, Mac and Victorinox through specialist retailers, but Victorinox's own page omits both. Weight is on brand pages and is reliable there.

### Retail listings (Amazon product pages, curl, product-information rows)

| ASIN | Product | Rows present (verbatim values) |
|---|---|---|
| B008M5U1C2 | Victorinox Fibrox Pro 8 in | Blade Material = Stainless Steel; Blade Edge = Plain; Length of Blade = 7.9 in; Weight = 6.1 oz; Item Weight = 22.68 g; Construction Type = Stamped; Dishwasher safe = ✓; Item Type Name = Chef's Knife. No HRC, no angle. |
| B00009ZK08 | Wüsthof Classic 8 in | Blade Material = Stainless Steel; Material Type = High Carbon Stainless Steel; Bolster = Full Bolster; Knife Edge = Straight Edge; BladeLength = 8 inches; Item Weight = 3.84 ounces; Construction Type = Forged. HRC only in a bullet: "tempered to 58-degree HRC". |
| B0000Y7KNQ | Shun Classic 8 in | Blade Core = VG-MAX; Steel Layers = 68 Layer Damascus; Rockwell Hardness = 60-61; Item Weight = 206 g; Construction Type = Forged. Angle only in a bullet: "16-degree edge". |
| B000N5H2XU | Mac MTH-80 | Blade Edge = Hollow; BladeLength = 13 inches (the overall length); Item Weight = 10 ounces; Construction Type = Forged; bullet "Not dishwasher safe". No HRC. |
| B000XSX8IA | Misono UX10 21 cm | Blade Material = Stainless Steel; BladeLength = 20 centimeters; Item Weight = 0.16 kg; bullet "asymmetrical edge". No HRC. |
| B001TPE0VU | Masamoto CT gyuto | Blade Material = Carbon Steel; Rust-resistant = ✓; Bevel = Double; HRC = 57 (bullets say "HRc. 58-59"); Item Type Name = Gyuto Knives. |
| B073R72PBV | ZWILLING Gourmet 10-pc set | Included Components = 2.75" Peeling Knife, 3" Vegetable Knife, 4" Paring Knife, 5" Serrated Utility Knife, 6" Slicing Knife, 8" Bread Knife, 8" Chef's Knife, 9" Steel, Rubberwood Block, Scissors; Construction Type = Stamped. |
| B00AL1J1IU | Wüsthof Come-Apart Kitchen Shears | title "Come-Apart"; Hand Orientation = Ambidextrous; bullet "Not dishwasher safe". |
| B000KILLXM | OXO Good Grips Multi-Purpose Kitchen Shears | Blade Edge = Serrated; Hand Orientation = Ambidextrous; bullet "Blades separate for thorough and easy cleaning". |
| B001CA5LZ6 | Chef'sChoice 1520 | title "for 15- and 20-Degree Straight-Edge and Serrated Knives"; Material = Diamond; Grit Type = Fine. |
| B01FYEYKD4 | SHAPTON Ha No Kuromaku A-set | title "Medium Grit (#1000) + Fine Grit (#5000)"; Grit Type = Medium Grit,Fine Grit; Material = Ceramic. |

What this tells the scraper: on 6 of 6 knife listings, blade material, blade length and an item-type row are present, and construction (forged or stamped) on 5 of 6. Rockwell hardness is a row on 2 of 6 and in a bullet on 1 more. Edge angle is never a row (1 of 6 in a bullet). Item weight is wrong on 3 of 6 (Victorinox 22.68 g, Wüsthof 3.84 oz, Mac 10 oz, against 165 to 266 g on the brand spec), so `blade_weight_g` is marked researched. Blade length is wrong on 1 of 6 (Mac). Amazon's "Rust-resistant" tick on a carbon-steel Masamoto shows the material row cannot be trusted for rust. Shears listings carry take-apart in the title or bullets and hand orientation as a row. Sharpener listings carry angle class and grit in the title.

### Primers

**Wikipedia, Sharpening stone (raw wikitext)** https://en.wikipedia.org/wiki/Sharpening_stone
- verbatim: "a higher number denotes a higher density and therefore smaller particles, which give a finer finish"; table: "1000-2000 || 8 μm || Fine, will leave a blade sharper than most factory edges"; "4,000 || 4 μm || Ultra-fine"; "There is no dominant standard for the relationship between 'grit size' and particle diameter."
- Supports: second source for the grit ladder (about 1,000 to sharpen, 4,000 to 6,000 to finish). Confidence medium (encyclopedia citing retailer charts).

**Wikipedia, Santoku (raw wikitext)** https://en.wikipedia.org/wiki/Santoku
- verbatim: "Standard santoku blade length is between 15 and 18 cm ... in comparison to the typical 20 cm European cook's knife."; the santoku "has limited 'rocking' travel".
- Supports: santoku lengths and motion. Confidence medium.

### Could not reach

Wirecutter guides (nytimes.com blocks curl, no Wayback snapshot of the chef's knife guide), Serious Eats shears and whetstone pages (no snapshot), the Wüsthof brand page (renders by script), UK legislation on knife sales to under-18s (legislation.gov.uk returned an empty page; not used), NSF/ANSI 2 page (no usable text), r/chefknives wiki (not attempted after the search budget ran out). Mandoline reviews were not found before the budget ran out.

## Data points used for derived metrics

Quantified Knife Project, 8 in class chef's knives, verbatim from each page ("measured (advertised)" angle per side; hardness as stated; weight; CATRA total cardstock cut):

| Knife | Steel | Angle measured (advertised) | HRC | Weight g | TCC mm |
|---|---|---|---|---|---|
| Wüsthof Classic | stainless | 14.5 (14) | 58 | 269.5 | 365.9 |
| Wüsthof Classic Ikon | high carbon steel | 15.5 (14) | 58 | 272.02 | 303.3 |
| Wüsthof Amici | Wüsthof steel | 13 (14) | 58 | 229.88 | 299.1 |
| Henckels Classic | X50CrMoV15 | 15 (15) | 55-58 | 231.52 | 318.2 |
| Zwilling Solution Fine Edge | stainless | 14.5 (15) | 50-54 | 151.52 | 361.5 |
| Mercer Renaissance M23510 | high carbon stainless | 14 (15) | 56 ± 1 | 231.44 | 231.7 |
| Messermeister Royale Elite | 1.4116 | 13.5 (15) | 57-58 | 204.7 | 242.3 |
| Victorinox Swiss Classic | high carbon stainless | 13.5 (15) | 56 | 131.35 | 230.6 |
| Victorinox Swiss Modern | high carbon stainless | 12.5 (15) | 56 | 131.35 | 371.8 |
| Misen Ultimate | AUS-10 | 11 (20) | 58 | 230.89 | 415.6 |
| Material 8 in | high carbon stainless | 13 (13) | not provided | 242.73 | 428.2 |
| Mac Professional MTH-80 | AUS 8 | 14 (15) | 61 | 196.04 | 426.3 |
| Tojiro Professional 8.2 in | VG10 + 13 chrome | 14 (12) | 60 | 197.25 | 411.1 |
| Shun Classic Hollow-Edge | VG-MAX | 20 (16) | 60-61 | 178.97 | 334.3 |
| Miyabi Koh | FC61 | 14.5 (12) | 61 | 178.07 | 383.8 |
| Miyabi Kaizen II | FC61 | 8.5 (9.5) | 61 | 199.11 | 1046.5 |
| Moritaka Hamono 9.4 in | Aogami Super | 4 (11) | 64 | 175.73 | 647.1 |

Arithmetic on the 16 rows with an HRC (range midpoints used): correlation of HRC with TCC r = 0.53, of measured angle with TCC r = -0.63, of HRC with weight r = 0.09. Rows at 58 HRC or under (10 knives) weigh 131 to 272 g with median TCC 311 mm; rows above 58 (6 knives) weigh 176 to 199 g with median TCC 419 mm. Every knife clears the ISO 8442-5 type A floor of 150 mm (lowest 230.6). Measured angles on 15 of 17 sit between 11 and 15.5 degrees; ATK's own measurements say 13 to 16 for its lineup. Misen's "20° advertised" against 11 measured may be an inclusive figure printed as per side; I have no source either way.

Hardness bands, two independent sets: Serious Eats (Donald) gives Western 52 to 58 and Japanese 58 to 65. Brand figures from Cutlery and More and QKP: Wüsthof 58, Zwilling Pro 57, Henckels 55-58, Messermeister 57-58, Mercer 56, Victorinox 56, against Shun 60-61, Mac 60 or 61, Tojiro 60, Miyabi 61, Moritaka 64. Global G-2, a Japanese brand, states 56 to 58, so origin and hardness class do not always match.

Weights: German forged 229.88 to 272.02 g (QKP), 265 and 266 g (Cutlery and More); Japanese-style 175.73 to 212 g (QKP; Cutlery and More Shun 212 g, Mac 196 g, Global 170 g); Victorinox 131.35 g (QKP), 165 g (Cutlery and More), 5.9 oz = 167 g (ATK), 6.4 oz = 181 g (Victorinox brand page). Serious Eats' sweet spot of 7 to 8 oz is 198 to 227 g.

Sets: ZWILLING Gourmet 10-pc = 7 knives + steel + shears + block (Amazon Included Components). Core three (chef's, paring, bread) all present. So `knives_in_set` = 7 of 10 pieces and `cost_per_core_knife` = price / 3.

## Against the existing add-on schema

Add-on read: `supplies/kitchen/add-ons/knife.jsonc` (sizing.blade_length, blade_steel enum, edge_grind enum, rockwell_hrc, full_tang, grit_raw), composed with `kitchen-standard.jsonc` (materials with roles, max_heat_temp, dishwasher_safe) and `supplies-standard.jsonc` (high_signal_markdown, sizing: size_stated, pack_count, pieces_included_text, dimensions, capacity, weight, measurements_text). Kinds below use AGENTS.md's four: vertical anchor, category quality currency, hard filter, sizing; anything else is high_signal_markdown.

| Facet in this register | In add-on today | Proposed kind under AGENTS.md | Note |
|---|---|---|---|
| tool_type | no (the leaf has no product-type enum) | hard filter | Proposal: `tool_type` enum [knife, knife_set, kitchen_shears, sharpener_whetstone, honing_rod, other_cutting_tool]. The leaf bundles four product families with disjoint specs; without it `grit_raw` and `rockwell_hrc` share rows with shears. |
| knife_type | no | hard filter | Proposal: `knife_type` enum [chefs_gyuto, santoku, paring, bread_serrated, utility_petty, boning_fillet, slicing_carving, cleaver_nakiri, steak]. Amazon's Item Type Name row carries it on every knife listing read. |
| blade_length | yes, `sizing.blade_length` | sizing | Keep. Correctly inside sizing (8 in and 10 in variants are the same listing). Check against the title: Amazon gave Mac's overall length as blade length. |
| rockwell_hrc | yes, `rockwell_hrc` | category quality currency | Keep, and store ranges as a min and max (Shun 60-61, Global 56-58, Henckels 55-58) rather than one number. Worth augmenting from brand spec tables. |
| hardness_class | no | derived at query time | From `rockwell_hrc`; not a stored field. |
| edge_angle_deg | no | category quality currency | Proposal: `edge_angle_per_side_deg` (number or min/max). Needed to match a sharpener and the only geometry number brands publish. In Amazon bullets at most; brand spec tables carry it. |
| steel_type | partly, `blade_steel` enum | hard filter | The enum mixes three axes: corrosion (stainless, carbon_steel), construction (damascus_layered), process (powder_steel). Proposal: a boolean or enum `rusts` [stainless, carbon_core_clad, carbon_throughout] as the filter, and drop `damascus_layered` and `high_carbon_stainless` from the enum (cladding is a photo fact; "high carbon" has no official threshold per Serious Eats). |
| steel_grade | no | high_signal_markdown | X50CrMoV15, VG-MAX, Cromova 18, AUS-8. Text for the markdown line, not a column. |
| edge_grind | yes, `edge_grind` | hard filter | Keep; add `asymmetric_double_bevel` (Misono UX10's listing says "asymmetrical edge") and a handedness value for single bevel. |
| blade_weight_g | partly, `sizing.weight` in supplies-standard | sizing | Keep the standard field, but backfill from the brand page: Amazon's Item Weight was wrong on 3 of 6 knives. |
| edge_type | no | hard filter | Proposal: enum [straight, straight_dimpled, serrated]. Amazon carries it as Blade Edge / Knife Edge / Type of Edge. Decides bread and steak knives and sharpener compatibility. |
| catra_tcc | no | outside schema | Lab-only; top N from QKP-style tests. |
| core_knives_included | no; `pieces_included_text` holds the raw list | derived from pieces_included_text | Not stored. |
| shears_take_apart | no | hard filter (boolean) | Title and bullet text on both shears listings read. |
| sharpener_type | no | hard filter | Proposal: covered by the `tool_type` values above plus `sharpener_type` enum [whetstone, guided_system, electric, pull_through, honing_rod_steel, honing_rod_ceramic, honing_rod_diamond]. |
| sharpener_angle | no | hard filter | Proposal: enum [15, 20, 15_and_20, adjustable]. In the title on the Chef'sChoice listing. |
| whetstone_grit | yes, `grit_raw` | category quality currency (for stones) | Keep, but parse into numbers (#1000, #5000). |

Add-on fields this register considers noise: `full_tang` (the add-on's own comment says the claim is not photo-verifiable, and no source read here ties tang to performance; Wüsthof's "full Tang" is a bullet claim). `blade_steel: damascus_layered` (cladding pattern, which a photo shows; the core steel is what cuts). `dishwasher_safe` from kitchen-standard is kept as a field but needs a judgement beside it: the brand claim (Victorinox "Dishwasher safe: Yes") and ISO 8442-1's dishwasher-proof grades describe corrosion, while Serious Eats and ATK say dishwashers dull edges.

## Branches

Each leg names the register or notes sentence it follows from. Split facets are categorical or ordinal, so every `when` is a value of the split facet.

**Split 1, tool_type ("One knife, a set, shears, or a sharpener?")**
- when `single knife`: then_ask knife_type, blade_length.
  - knife_type: "Experts treat these as different jobs: a chef's knife or gyuto does most work" (knife_type, why experts care) and ATK's three essentials.
  - blade_length: "ATK found 8 in the most useful and versatile chef's length" (blade_length, why experts care).
- when `knife set`: then_ask core_knives_included. **Changed 2026-10-25**: dropped `makes_irrelevant knife_type`. The checker's A/C review found steak-knife sets need `knife_type` (value "steak knives" exists) and the core-three check is itself a test of knife types, so a set holding several types does not make the facet meaningless. `core_knives_included` now carries its own `cold_start_question` ("Want the chef's, paring and bread knife included?") instead of relying on an unstated one.
  - core_knives_included: "Reviewers say a set is worth it only if it holds the core three" (core_knives_included, why experts care; ATK, Serious Eats sets, Wirecutter). Most sets reviewers tested already include the three, so this rarely excludes a set on its own; `knives_in_set` and `cost_per_core_knife` do the real narrowing.
- when `kitchen shears`: then_ask shears_take_apart; makes_irrelevant knife_type, hardness_class, steel_type, edge_grind.
  - shears_take_apart: "ATK strongly preferred take-apart shears" (shears_take_apart, why experts care).
  - The four irrelevant facets are each defined as properties of a knife blade ("for a knife" in each definition), and ISO 8442-1 and -5 cover knives while CATRA tests shears with in-house protocols only (CATRA, verbatim above). Chain: the register scopes these facets to knives; shears are not knives.
- when `sharpener or hone`: then_ask hardness_class, sharpener_type, sharpener_angle; makes_irrelevant knife_type, steel_type, edge_grind. **Changed 2026-10-25**: moved `hardness_class` from `makes_irrelevant` to `then_ask`. The checker pointed out that `sharpener_type`'s own text ("a rolled edge can be reset with a honing rod, something that won't work well with the more brittle, harder steel") makes the buyer's own knife hardness the deciding input between a rod and a stone, so the leg was throwing away a dependency the register itself states.
  - sharpener_type: "Whetstones remove the least metal ... pull-through slots the most damage" (sharpener_type, why experts care).
  - sharpener_angle: "All sharpeners are designed to work with knives of specific edge angles" (ATK manual sharpeners, verbatim; sharpener_angle, why experts care). Applies only to guided and electric sharpeners; whetstones and honing rods have no value.
  - Irrelevant facets (knife_type, steel_type, edge_grind): same chain as shears.
- when `other cutting tool` (**added 2026-10-25**): makes_irrelevant knife_type, hardness_class, steel_type, edge_grind. Mandolines, pizza wheels and egg slicers now get a `tool_type` value instead of dropping out of every path silently (checker, Part B scope note); they still have no facets of their own in this register.

**Split 2, hardness_class ("Tough and easy to hone, or harder and holds an edge?")**
Answer mapping: "tough and easy to hone" = `tough, easy to hone (58 HRC or under)`; "harder and holds an edge" = `hard, holds an edge (over 58 HRC)`. Products are classed by stated HRC, ranges by their midpoint (hardness_class, definition and backfill note).
- when `hard, holds an edge (over 58 HRC)`: no branch (**changed 2026-10-25**; dropped `then_ask edge_grind, steel_type`). Both legs were rated WEAK by the checker and did not survive: every hard-class knife in the register's own data table (Shun, Mac, Tojiro, Miyabi, Masamoto CT) is double bevel, so "hard → single bevel" is not a step the register's sources support; and the Serious Eats sentence used for steel_type ("Japanese knives often have high levels of carbon") is immediately followed on the same page by "most of the Japanese knives I tested were pure stainless steel", so "hard → non-stainless" is also unsupported. `edge_grind` and `steel_type` remain ordinary facets (and `steel_type` is already split 3), just not branched from this value.
- when `tough, easy to hone (58 HRC or under)`: makes_irrelevant edge_grind.
  - Chain: (1) "Western knives usually have a double-bevel edge, shaped like a V" (Serious Eats chef's knives, verbatim); (2) the tough class is the Western cluster, Wüsthof 58, Zwilling 57, Victorinox 56 (hardness_class, why experts care). Every tough knife in the data table is double bevel. "Usually" makes this the weakest leg; kept because no single-bevel knife appears in any tough-class source read.

**Split 3, steel_type ("Stainless, or carbon steel you must dry straight away?")**
Answer mapping: "stainless" = `stainless`; "carbon steel you must dry" = `carbon (rusts if left wet)`, which includes stainless-clad carbon cores because the exposed edge is the core (steel_type, definition).
- No branches. The answer filters on itself and changes nothing downstream that the sources support.
- **Changed 2026-10-25**: removed `skip_if_known` entry "an earlier answer about dishwasher use". The mapping from a dishwasher answer to a steel_type value was never stated, and checker Part B flagged it as genuinely ambiguous: dishwasher use could mean stainless, or it could trigger the separate judgement that no good knife should go in a dishwasher at all.

## Trimmed detail

Sentences cut from capped fields that carried a fact, a number or a source:
- summary: "German-style forged knives weigh 230 to 272 g; Japanese-style 176 to 212 g; Victorinox's stamped chef's knife about 131 to 167 g" (kept in blade_weight_g).
- mechanism: Knife Steel Nerds' regression coefficients (15.8 mm per HRC, -17.8 mm per degree), single-source and kept only here; the ISO 8442-1 52 HRC floor (single document, here only).
- rockwell_hrc: Zwilling Solution's stated 50 to 54 HRC sits below ISO 8442-1's 52 HRC floor for resharpenable blades at its low end (QKP; IS 15104-1).
- edge_angle_deg: Misen advertises 20 degrees and measured 11; may be an inclusive number.
- shears_take_apart: ATK's "more than 30 degrees" cutter-blade wedge line; Shun 25 degrees, Henckels 50 degrees (ATK spec lines).
- whetstone_grit: "anything lower [than 800] is for repairing the blade" (Serious Eats quoting Middleton).
- steel_type: Serious Eats' "at least 0.6% carbon" informal high-carbon line.

## Corrections

No blind check has run yet. These edits came from my own STYLE.md pass before the first build was handed over (2026-10-25):
- blade_length: removed "a 6 in one small hands and small boards" (no source). The 10 in sentence is now credited to the knife seller Serious Eats quotes (Josh Donald: a Western 10 in knife "for cutting lots of cabbage ... or carving bone-in roasts").
- edge_type: removed "most whetstone advice does not [handle serrations]" (no source). It now names the Chef'sChoice 1520, which takes serrated knives, as an example.
- Judgement on honing rods: removed "or ceramic" (only a reader comment on Knife Steel Nerds supports it).
- Judgement on edge angles: sources_disagree set to false. ATK and Chef'sChoice agree that 20 degrees is the traditional figure and that current knives are narrower. The only "primers still say 20" evidence I had was search excerpts.
- rockwell_hrc and the HRC judgement: the Quantified Knife Project correlation is now labelled as our own arithmetic on their figures.
- blade_weight_g: the Japanese-style band 176 to 212 g now says "hard Japanese-style", because Global (Japanese, 56 to 58 HRC) weighs 170 g.
- The weight question is now "Heavy enough for squash and bone, or light and nimble?" because the old wording failed the generic test.
- Mechanism and rockwell_hrc now say "most Western brands", because Zwilling Solution states 50 to 54.
- Visual-grammar origins were reworded so the renderer's "Used today by" prefix reads as a sentence.

Viewer: `tests/viewer-browser.py` passed 6 of 6 (1380, 768 and 390 px, light and dark, offline) on a temporary copy in the scratchpad. I checked the 1380 light flowchart and the 390 dark full page by eye: tree labels are full size, map chips are legible, and the page does not overflow.

## Corrections after the blind check (2026-10-25)

Blind checker's report: `check.md`. Re-fetched sources myself (scratch dir `fix-knives/`): four new Quantified Knife Project pages (Made In, Hedley & Bennett, Global, Shun Classic non-hollow) plus Moritaka Hamono by WebFetch; re-pulled the Masamoto CT and Mac MTH-80 Amazon listings by curl and parsed them myself; re-pulled the Serious Eats carbon-steel page by curl to recheck the "11 knives" and "half" figures. ISO 8442-1/-5 wording fixes used the exact quotes already in this file's "Sources and what each supports" section; no refetch needed there.

1. Removed the Masamoto AT-column misread from `rockwell_hrc`'s why_experts_care, `steel_type`'s listing_field_hint and judgement 10 (check.md A8, required fix 1). Re-fetched and parsed the Amazon comparison table myself: columns are AT/VG/CT/ZA/SAYA/KS; HRC row is 57/58-59/58-59/60-61/no data/62-63; Rust-resistant row is ✓/✓/no data/✓/no data/no data. The CT column (this carbon-steel product) is 58-59 HRC and "no data" for rust-resistance, matching its own bullet ("58-59") and contradicting the register's claim of "57" and a rust tick. Rebuilt judgement 10 on the Mac MTH-80's "Blade Material: Alloy Steel" row (verified myself, a stainless knife) and the three wrong Item Weight rows; rockwell_hrc's example brand is now Henckels Classic (55-58), which is correctly sourced.
2. Corrected the edge-angle miss from "up to 4 degrees" to "up to 9 degrees" (edge_angle_deg backfill_note, judgement 3; required fix 2). Verified fresh: Made In 21.5° measured vs 12.5° advertised (9° gap); Hedley & Bennett 17° vs 11.5° (5.5° gap).
3. Corrected the CATRA low end from 230.6 mm to 188.7 mm (Made In) in catra_tcc's why_experts_care, range.typical, listing_field_hint and judgement 8; updated the Quantified Knife Project page count from "about 17/20" to 21 (required fix 3). Recomputed the HRC/angle-vs-TCC correlations myself on all 20 knives with a stated HRC: r = 0.42 for hardness, r = -0.54 for angle, matching the checker's figures exactly and replacing the register's r = 0.53 / -0.63 (computed on the original 16-17). Also removed the now-false "the lowest in the set read" from the qkp_victorinox_classic reference.
4. Reworked `core_knives_included` (required fix 4): gave it `novice_answerable: true` and a `cold_start_question` ("Want the chef's, paring and bread knife included?") since it had none and could not actually be asked; tightened backfill_note to require a full-size (8 in or longer) or explicitly named bread knife rather than any serrated piece (a 5 in serrated utility knife does not count, per Serious Eats); lowered `narrows_set` from 3 to 2 and noted in why_experts_care that most sets reviewers tested already pass, so `knives_in_set` and `cost_per_core_knife` do the real narrowing.
5. Removed "a query naming a Japanese style such as gyuto, santoku or nakiri, or a German brand" from hardness_class's `skip_if_known` (required fix 5). It contradicted the register's own origin-is-not-a-proxy rule; German brands sell santokus at 56-58 HRC.
6. Qualified the 13-to-16-degree claim as Western-only throughout (summary, mechanism, edge_angle_deg, judgement 1; required fix 6), and added the Japanese-style measured range of 4 to 20 degrees, sourced to the four newly fetched QKP pages plus Moritaka, Shun Classic Hollow-Edge and Miyabi Kaizen II (already in the register).
7. Restated the hardness bands: summary now says "58 HRC and up" rather than "60", and hardness_class's why_experts_care now gives Japanese-style as "mostly 58 to 65" (Shun 60-61, Hedley & Bennett 58-60) and labels the 58 HRC cut as this register's own call on an overlapping boundary, not a line any source draws (required fix 7).
8. ISO 8442-1 (inclusive_edge_angle, judgement 7; required fix 8): added the chopping/boning exception to the 40-degree cap; reframed the claim as "a voluntary material standard" rather than "the food-contact floor"; noted carbon-steel blades sit outside Table 1; stopped counting IS 15104-1 as an independent second source (it is an identical adoption of the same text). Did **not** add clause 6.4's 52 HRC floor — see rejected finding below.
9. ISO 8442-5 (edge_type, CATRA grammar; required fix 9): corrected edge_type's why_experts_care so type B is defined by "not intended to be resharpened on a steel" rather than equated with "serrated" (coarse serrations with a pitch over 1 mm are type A); the CATRA bar grammar and catra_tcc's why_experts_care now say the 150 mm floor is for type A (plain) edges specifically.
10. Branch legs (required fix 10): dropped hardness_class "hard" → `then_ask edge_grind, steel_type` entirely (both legs' source sentences did not hold up — see the Branches section above); moved `hardness_class` from `makes_irrelevant` to `then_ask` on the "sharpener or hone" tool_type branch, since sharpener_type's own text makes the buyer's knife hardness the rod-vs-stone input; dropped `knife_type` from `makes_irrelevant` on the "knife set" branch (steak-knife sets need it); clarified in sharpener_angle's backfill_note that it applies only to guided and electric sharpeners.
11. Scope (required fix 11): added an "other cutting tool" value to tool_type, with a branch that makes the knife-only facets irrelevant, so mandolines, pizza wheels and egg slicers get routed to a value instead of dropping out of every path silently. Steak-knife sets are resolved by #10: `knife_type` stays live on the "knife set" branch, so a steak-knife set is `tool_type = knife set` with `knife_type = steak knives`, not a separate case.
12. Corrected the Serious Eats carbon claim (steel_type why_experts_care, se_carbon reference; required fix 12): re-fetched the archived page and confirmed "I tested 11 of them" and "about half ... were non-stainless carbon steel ... started picking up spots". The register's "about half of the 11 carbon-labelled knives ... spotted" conflated the two; it is now "every non-stainless knife among the 11 ... spotted ... and about half of the 11 were non-stainless".
13. Fixed the Light stamped Western weight range (mechanism.families, blade_weight_g; required fix 13): 131 g is the Quantified Knife Project's Victorinox Swiss Classic (also on Swiss Modern, a suspected copy error), not the Fibrox Pro; the Fibrox Pro itself runs 165 g (Cutlery and More) to 181 g (Victorinox's own page, 6.4 oz).
14. Softened "edge angle mattered at least as much as hardness" to "hardness moves edge retention more than a one-degree change in angle" (mechanism, rockwell_hrc why_experts_care; required fix 14), matching the corrected r = 0.42 / -0.54 correlations from #3.
15. Backfill costs (required fix 15): knife_type and sharpener_type moved from "none" to "low" with new backfill_notes (free-text Item Type Name parse; title-word parse since the Material row does not separate sharpener types); edge_angle_deg and rockwell_hrc moved from "low" to "medium" (measured edges miss stated ones by up to 9°; HRC claims are unverified past the brands a specialist retailer stocks); sharpener_angle and whetstone_grit listing_field_hints now say they rest on one listing each (Chef'sChoice; Shapton); shears_take_apart's backfill_note now says a missing take-apart word means unknown, not one-piece; edge_type's backfill_note now says to ignore Blade Edge values that are not an edge type (e.g. "Chef's Knife", "Fine").
16. Reworded edge_grind's cold_start_question from "Right- or left-handed?" to "Double bevel, or single bevel (pick a hand)?" (required fix 16), since a right-handed answer did not map to any value; backfill_note now says a single-bevel answer needs a handedness follow-up.

Extra fix beyond the numbered list: removed steel_type's `skip_if_known` entry "an earlier answer about dishwasher use" (check.md Part B, Split 3). The mapping from a dishwasher answer to a steel_type value was never stated and is genuinely ambiguous — see the Branches section.

Rejected finding: required fix 8's closing sentence, "Consider adding the clause 6.4 floor of 52 HRC for type A edges, since the split is on HRC." Not added. Clause 6.4 appears only in IS 15104-1, a single document (the original ISO 8442-1:1997 PDF I have does not contain it), and the one knife whose stated range straddles it — Zwilling Solution Fine Edge, 50 to 54 HRC — has no individual reference entry in this register; it exists only in this notes file's data table, sourced from a Quantified Knife Project page I did not fetch for this pass. Adding a numeric floor on single-document sourcing, with no product in the register's own evidence to apply it to, would violate the two-source rule for no real benefit to a buyer-facing register.

## Script and schema problems

- `schema.json` has no `supplies` value for `vertical`, so the brief's instruction to set `"vertical": "supplies"` cannot validate. Used `"other"`. Same failure is visible on `labels/category.json` in this folder.