A cheapie. Warren came to mind when I was using this, but not for the steel (it's high speed steel). It's a mujingfang chisel that is not beveled or tapered on along its thickness (at least not enough to matter), but along its length. It has almost no resistance when cutting mortises, and maybe it doesn't clean the sides of the moritse, but that doesn't much matter for planes.
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(warren comes to mind because he has often pointed out that vintage mortise chisels were tapered along their length, too, something that appears to have gone the way of the dodo bird once chisels were mass produced)
These muji chisels would be cheap if they were offered individually - they're about $8 each, but they come in a set of medium, medium wide, wider than you'd use, wider than that and wider than that yet, and the shipping on a set of 5 of them from china is expensive (about $30). So they end up not being that cheap, and their tang isn't real long which will necessitate an eventual fix.
I won't be making a second of this plane, I've got no tools for skewed planes (no floats cut to fit in a corner) and have done all of the work with chisels, except for the bed.
I had a salvage double iron, well not salvage - sacrifice. Sacrificed an english badger plane because skewed double irons are not easy to find, but a double iron will be a necessity to making this plane cut against the grain in all woods. Badger planes have some lean (the iron at the bottom is at the edge, but not at the top), which messes up skewing if you don't do them that way. I chose to not have lean on this plane, and since it's raised panel only will let up the plane at the side of the mouth a millimeter or so such that the cut bottoms out.
Anyway, eliminating the lean changes the skew angle from 20 to 28 which could be problematic (and definitely would if the cut used the entire iron, but this one only uses about 80% of it, so I'm hoping that will save me). Double iron planes don't love extreme skew angles, but it's no issue on a normal bench plane because you never have to skew it to eliminate tearout.
Guessing at all of the angles has been a complete pain, and working up low effort ways to find out where they'll need to be (for example, the 28 degree skew required to get the iron to bed such that at a 45 degree bed, the cap iron will be lined up with the edge so that it actually works to prevent tearout). And then making and fitting the wedge, which results in a lot of dragging a wedge with no square sides over a plane stuck upside down in a vise. Fortunately, such things set up with the cap iron set close don't actually cut the skin on your hands. The angle on the wedge is dependent on the skew and the bed of the angle in combination, so if you blindly cut it at 28 degrees, it won't fit, it's somewhere around 20 or 21 (I guessed at the angle divided by the square root of 2, which was close).
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The reason I'm letting up the edge instead of leaning the iron out (so that it cuts at the edge of the plane) is that letting up the edge and keeping the iron tucked in gives me the option to add a wedged nicker later if it seems like it will be helpful (if the finish isn't good cross grain).
Random thought, the front of the mouth, front corner at the edge, is always an erosion point for skewed planes. That edge wears in 3d, and then these planes have a problem feeding. I've left the mouth a little wider than you'd leave with a single iron plane, because double irons like a mouth tight or loose, but not between. I'll eventually put a brass wear strip there.
The work could be a lot neater, adding the skew makes everything you normally look for (a coplanar bed, etc) a challenge. The eyes are gigantic because I tried cutting them a little differently this time and had to redo them twice. Lost cause, mostly due to picking the worst blank from my new pile of beech - intentionally, so as to leave the good ones for planes that I know will turn out good.
Here's the donor plane. My shop has become a dangerous place for a plane that has a good iron.
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"modern" steel is a bit of a departure from normal for me, but this chisel, which is super tough, even at sub 30 degrees, sharpens nicely on a dry diamond hone and then believe it on not, on an okudo suita (japanese natural), which raises black swarf fairly quickly and doesn't allow an organized wire edge to form on the finished edge. This is a chisel that is a bit much for a king stone, and that gums up a shapton. This is the first time I've ever seen a natural stone outdo most of my synthetics for finish work, but it's a very strong cutting stone that most will not come across buying low priced natural stones.