Calculator › Knives › Fillet knife
A fillet knife is the thinnest blade in the shop: 0.040–0.070 in at the spine for a 6–7 in blade (up to 0.100 in for a 10 in salmon knife) so it flexes along the bone. That thin, it is stock removal only, and stainless is strongly preferred because the knife lives around fish and water. AEB-L in 0.040–0.062 in is the classic choice and is sold in sheet and narrow bar.
Width is under 1 in for most of the blade, so 1 × 1/16 in stock in 36 in lengths gives three blades. Keep the tang the same thickness and let the handle do the stiffening.
Stock removal: the bar is cut to blade + tang + clean-up, so the tang section and forged thickness below only change the finished-weight estimate. Switch to Forged and they change the stock length too.
Tang dimensions are estimated from the tang style until you change them. Measuring yours is worth doing — a forged blank's length depends on the tang's cross-section, not on what the tang is called.
Stock removal: fill factors only change the finished-weight estimate here. They set the stock length when the method is Forged. Grinding loss has no effect at all in stock removal — the bar is cut straight to the profile, nothing is drawn out.
The fraction of the blade's and tang's bounding box that is actually steel once the bevels are ground. Distal taper is factored in separately now (see "Distal taper" below, under What this assumed) and isn't editable here yet — these two fill factors are the ones worth replacing with your own measurements: weigh a finished blade, then adjust until the finished weight below matches the scale.
Steel is only part of the cost. Add abrasives, handle, heat treat and your time, and see the price that actually pays you.
Copy link to this calculationOne job, done well: running a blade along a fish's backbone and rib cage, and separating flesh from skin. The blade bends so it can follow the skeleton and stay in the plane of the skin, which is what keeps meat on the fillet instead of on the frame. It is not a boning knife for red meat and it is not for prying at joints or cutting through heavy bone.
The modern pattern has a clear origin. Ron Weber, a Minneapolis fishing-tackle rep, sketched a consumer fillet knife after the well-worn knives he had seen in commercial fish houses (blades thinned and made flexible by years of sharpening) and took the drawing to the Finnish maker Marttiini. Marttiini doubted it could be made; knives of the time were not that slender or flexible. Weber committed to buying twenty thousand of whatever came back. The Rapala Fish 'n Fillet launched in 1967 with a leather sheath and, later, a booklet titled How to Clean a Mess of Fish Without Making a Mess of the Fish. Most anglers were still hauling their catch to a processing plant. More than sixty million have sold since.
Flex is a spec, not a virtue: more is not automatically better. High flex suits skin removal and small soft-fleshed fish; medium is the versatile choice if you clean several species; stiff is for large, dense or thick-skinned fish and heavy ribs. Length tracks the fish, though the guides differ on where the bands sit: roughly 5–7 in for panfish, 7–9 in for walleye and bass, 9 in and up for salmon and big saltwater. Stainless is close to mandatory (this knife lives in slime, blood and salt water away from a sink) and the old line that stainless will not hold an edge does not survive contact with modern fine-grained stainless: AEB-L was developed as razor-blade steel, has carbides of a micron or less, and Larrin Thomas puts its edge retention slightly above 1095, O1 and 52100. Two other things get returns: too much hardness in a blade that must bend to its elastic limit and spring back, and a beautiful stabilised handle that turns slick the moment it is wet.
Thin stainless moves in heat treat. Plate quench between aluminum blocks straight out of the foil, and temper twice before you look at the edge or you will chase a warp that was going to relax anyway.
| Panfish, 5 in blade | 3/4 × 0.040–0.050 in |
|---|---|
| Standard, 7 in blade | 1 × 1/16 in |
| Salmon, 9–10 in blade | 1 1/4 × 3/32 in |
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.
Not sensibly. At 1/16 in the steel loses heat in seconds and warps if you look at it. Grind it from thin stainless stock.
Bar sizes for ten common knife patterns, weight per inch for every standard flat bar, and quick heat-treat numbers for the usual carbon steels. Print it, tape it to the grinder.