Monitor Lizard D2 Tool Steel Original Filipino Balisong butterfly Knife BF-82

The BF-82 Monitor Lizard is a 29cm balisong with a 14cm D2 blade, 220g, brass and kamagong. A monitor lizard is the big one in its family and this is the big one in ours. It is also the right page to explain what D2 actually is, because the phrase “tool steel” does a lot of work in knife marketing and very little explaining.

D2 is not stainless, and that is the interesting part

D2 is an air-hardening tool steel developed for industrial dies: the punches and forms that stamp sheet metal by the million. It was never designed for knives. It ended up on knives because the property that makes a die last, resistance to abrasive wear, is the same property that makes an edge last.

Roughly one and a half percent carbon, which is high, and eleven to twelve percent chromium. That chromium figure is the whole story. The conventional threshold for calling a steel stainless is about thirteen percent, and D2 sits just underneath it. Hence “semi-stainless”, which is a real description rather than a marketing hedge: it resists corrosion far better than plain carbon steel and not as well as 440C or VG10.

Where the edge retention comes from

Chromium at that level does not dissolve evenly into the steel. It forms carbides, which are hard particles suspended in the softer matrix around them, and D2 has a great many of them and they are large.

Those carbides are what saw through cardboard and rope long after a finer-grained steel has given up. They are also, unfortunately, harder than the abrasive in an ordinary ceramic stone, which is why sharpening D2 with ceramic feels like polishing rather than cutting. You need diamond, and you need patience.

Who D2 is genuinely for

The person who wants to sharpen a knife twice a year and otherwise be left alone. That is not a compromise position, it is a legitimate preference, and D2 serves it better than anything else in our range.

Who it is not for: anybody who enjoys sharpening. If a stone and ten quiet minutes is part of why you own a knife, D2 will frustrate you and our high carbon knives will not. We sell both and we would rather match you to the right one.

We run this D2 balisong at 58-60 HRC

D2 can be taken higher. Some makers do. On a balisong we do not, because a knife that gets thrown around your knuckles meets a hard floor sooner or later, and a carbide-heavy steel at 62 chips when it lands. At 59 the edge rolls instead, and a rolled edge is a stone and some time while a chipped one is a regrind.

Twenty-nine centimetres and 220 grams

The traditional Batangas frame, called veinte y nueve by the smiths who set it, and the size a balisong was before the export market decided everything should fit in a pocket.

A longer handle sweeps a longer arc, so the knife rotates more slowly for the same wrist movement. That extra fraction of a second is where you spot a mistake and fix it. What it does punish is a loose grip, because there is more knife and 220g will find out whether you were paying attention.

Kamagong as a balisong handle

Philippine ebony, dense enough to sink in water and close-grained enough that it barely takes an oil finish and needs none. It will not crack, shrink or swell, and it will take a soft polish where your hand sits over a few years. Against polished brass, near black, which is most of what this knife looks like.

Ordering this D2 butterfly knife

The unsharpened trainer is the same knife, chosen above Add to Cart. On a 220g knife with a 14cm blade that is a serious recommendation rather than a beginner’s option.

A fitted leather sheath is in the box, cut for the 29cm frame. Sheaths sold separately are almost always cut for the 24cm standard and will not close over this one. US shipping is free, flat $49 to anywhere else for the whole order.