What size steel for a petty?

A petty is a short kitchen knife, and its height at the heel sets the width of the bar. The preset is a 5 1/2 in blade (about 140 mm), 1.15 in tall at the heel, with a 3/32 in (0.094 in) spine and a 4 3/4 in full tang for a straight Western handle. Add 1/8 in for clean-up and you need 1.275 in, which rounds up to 1 1/2 in. That makes it 1 1/2 × 3/32 in flat bar, forged or ground. A petty up to 1 1/8 in tall still fits 1 1/4 in bar, which by stock removal takes about 5 1/2 oz of bar instead of 6 3/4 oz.

The matching KraftyDesign blank (the "Draw this blank" link) is a small gyuto shape, with a heel and a pointed tip. The handle is straight and lines up with the spine. KraftyDesign starts Japanese patterns at 3/32 in, the same as this preset.

Spec listings from seven knife shops in the US, the UK and Australia cover nine pettys sold as 135 or 150 mm. They are 28.1 to 33 mm (about 1.1 to 1.3 in) tall, so the preset's 1.15 in (29.2 mm) sits among them. The two at about 28 mm would come from 1 1/4 in bar, and the other seven need 1 1/2 in. Their spines run from about 1.6 to 2 mm (0.06 to 0.08 in) at the thickest listed point, and five are 2 mm. The bar has to be at least as thick as the finished spine, and even the two thinnest are a hair over 1/16 in, so the calculator puts all nine on 3/32 in (2.4 mm) bar. The preset keeps that full 3/32 in at the spine, a bit thicker than any of them.

Some makers go thinner. In a KnifeDogs thread on pettys, one poster who makes and sells 5 to 6 in pettys does a few at 0.125 in and most of them thinner. Another usually makes his in 1/16 in. Set 1/16 in and the bar becomes 1 1/2 × 1/16 in. In 1084 the calculator then warns that 1/16 in is under the 0.09 in usually thought practical, and to expect warping in the quench. By stock removal, AEB-L gets no warning. At 3/32 in by stock removal, 1095, W2, O1, 15N20, 52100, AEB-L, CPM-154 and MagnaCut give the same bar with no flags. 80CrV2 and A2 get the warping warning. 14C28N is flagged because it is not commonly listed in 3/32 in.

The calculator starts on stock removal, which takes the whole 10 1/4 in profile plus clean-up: 10 1/2 in of bar per blade. That is about 6 3/4 oz of bar for a blade that finishes around 4 oz. The 12 and 18 in bars give one blade each, 24 in gives two, 36 in gives three and 48 in gives four. All but the 18 in cost the same per blade. The shops list their nine at 61 to 108 g (about 2 to 3 3/4 oz), handle and all as far as they say. The calculator's 3.9 oz is for the steel alone and is still more than any of them, so the estimate may run heavy. Weigh your first one and adjust the fill factors under Calibration.

Forged, the blade stretches (a 1.38:1 draw), so about 7 3/4 in of the same bar (about 5 oz) is enough. The blade finishes just under 3 1/2 oz. A 12 in bar gives one, 18 in gives two, 24 in gives three, 36 in gives four and 48 in gives six. The 24 and 48 in bars tie for the lowest cost per blade. To start thicker and forge down, set "Forged thickness" to "One size up". That starts you at 1 1/2 × 1/8 in, and it only applies in forged mode. The calculator won't forge AEB-L, CPM-154, 14C28N, MagnaCut or A2. Pick any of them and it works out the bar as stock removal, even with Forged selected.

What a petty is for

A petty is a small Japanese kitchen knife for the jobs a chef's knife is too big for. Wikipedia calls it the Japanese equivalent of a paring knife or utility knife. It describes a smaller knife for paring or for smaller produce, often used alongside the gyuto. Sakai Ichimonji Mitsuhide, a knife maker and shop in Osaka, says a petty is ideal for detailed prep such as peeling, slicing and decorative work. It adds that professional chefs often use a short 125 mm blade for peeling and cutting, and that 150 mm is popular for home use. Knifewear, a Canadian knife shop, sorts pettys by length. It says the 75 to 100 mm ones are also called paring knives and suit cutting in the hand. It calls 120 to 135 mm "the Goldilocks size", able to do a little paring and to cut fruit and vegetables on the board. It calls 150 mm "the carnivore's petty", the best knife for trimming fat and silver skin. For a cook who wants a small knife kit, Knifewear says, it can take the place of a honesuki or a boning knife. Bernal Cutlery says that from 150 mm up they make good line knives and small slicers. The 140 mm preset sits in the middle of these ranges.

Wikipedia lists the petty among Japan's double-bevelled knives, with the gyuto, the santoku and the sujihiki. Not every edge is even, though. Korin, a Japanese knife shop in New York, lists one 150 mm petty with an 80/20 bevel. In the same KnifeDogs thread, the poster who makes and sells pettys says the vast majority of the Japanese ones he sells, and all the ones he makes, are double bevel. Another poster tried a single-bevel petty and could never get used to it. America's Test Kitchen (ATK) compared pettys with Western utility knives. ATK says pettys have changed very little and still have straight-edged, triangular blades. The ones it tested measured 58 to 64 HRC. The Western utility knives were softer, at 55 to 58 HRC, and three of the four had curved edges. ATK says the line between the two has become somewhat blurred, and its advice is to buy by function, not by name. Of the nine shop pettys above, five list a Western handle and one a Japanese wa handle. The preset's full tang suits the Western kind. Wikipedia dates Japan's uptake of French and German cutlery ideas to the Meiji period, late in the 19th century, but gives no date for the petty itself.

None of what follows could be confirmed. The name and the date come from knife sellers and a knife magazine that cite no records, so treat them as shop talk, not settled history. Knifewear says "petty" is a word the Japanese borrowed from the French petit, meaning small. BLADE Magazine says the name comes from petit too. ATK quotes Josh Donald, who owns Bernal Cutlery, as saying the word is likely derived from petit. ATK also reports that, as Donald explains in his book, the petty first arose during the Meiji era. In that account, the petty, like the gyuto, was a Japanese answer to the utility knife and chef's knife they saw in Western-led kitchens. The same account says the utility knife, sometimes called an office knife, came from Europe, and that in its earliest form it was used to clean and process wild game. None of these sources names a maker or a year for the first petty.

Stock for a petty

In a BladeForums thread on stock thickness for kitchen knives, one poster tells the thread starter to begin with 2 mm stock and make smaller kitchen knives (petty) until they get the hang of it. Another works in 0.07 in 1084 and gets a little warping on some blades, but says most are fine or can be fixed. A BladeForums sale listing for a petty kiritsuke in 14C28N gives it as 2.5 mm thick at the heel (the listing calls that 3/32 in), tapering to the tip, and 36 mm tall at the heel. In the calculator that height takes 2 in bar.

Widths assume blade height + 1/8 in rounded up to stock; thickness is the finished spine rounded up. Change the inputs above for your own pattern.

Steels that suit it

Questions