In this video, I introduce the Nubatama Bamboo 220 Grit Stone. It is a pink coarse stone. I will be thinning two knives, making the area behind the edge thinner or more acute. The first knife is a Sanetu santoku, a clad ZDP-189 steel. This steel is a powdered metal from Hitachi metals, known for its very high chromium content (20%) and high carbon content (3%) which takes a very fine acute edge. It is known to be a somewhat abrasion-resistant steel, despite it not having any vanadium carbides.
The second knife is an Aogami Super or Super blue Spyderco Mule, wrapped with green paracord. I am continuing to thin this knife towards a zero grind edge a little at a time. Initially it has a convex edge on both sides and I am thinning this convex edge to a more acute convex edge.
In both instances, this is a very labor intensive process requiring a stone with superior abrasive power that will dish very slowly.I am specifically not concentrating on the actual edge, but rather the area behind the edge.
The stone is relatively porous, requiring just a few minutes to become fairly well saturated. It produces a grayish mud combining the mud and metal. The mud aids in producing an aggressive level of abrasion.
I comment on using the whole area of the stone to distribute wear evenly to reduce the requirement to do as much flattening.
I use the whole surface of the Spyderco knife to look at the abrasion characteristics, since the entire knife is unclad. The resultant finish is somewhat hazy. The stone is quite capable of thinning the steel behind the edge, which was the goal of this procedure.
The stone produces a moderate amount of mud and overall is a very capable stone for rapid metal removal, yielding a good but hazy finish on Aogami Super steel.
I then go on to thin an extremely abrasion-resistant powdered metal steel Sanetu ZDP-189 santoku knife. The stone does accomplish this quite successfully. I demonstrate the increase in bevel size, the level of finish of the bevel.