This morning I sharpened all the blades and did some experimentation with the plane.
I mentioned before that I've done something a little unconventional on this plane (for reasons that will become clear later in this post) by not having a sprung cap iron. The usual approach with a cap iron is to have a curve in it so that the tip is clamped rigidly down near the cutting edge to ensure there's no gap for shavings to get trapped. My cap iron is flat. To get that same effect of having a gap-free join at the tip, I run a burnisher across the tip in a similar way to how you might with a card scraper:
That produces a tiny roll-over of the tip, which then gets collapsed back down as the cap iron is screwed to the blade and hopefully ensures a gap-free join.
I grabbed a bit of sycamore out of the pile and attacked it with the plane:
It cuts really nicely and, with the low cutting angle, is very easy to push through the wood. I had a couple of instances of shavings getting caught between one corner of the blade and the brass base, so I might open up the mouth a little at some point, but I'd rather be in the position of needing to open it up than needing to close it!
The low cutting angle (36°) also means that it glides through end grain really easily for shooting:
I feel I ought to discuss the cutting angle a little more on this plane as it explains some of the more unusual design decisions. This is a cross section of the plane:
Ignore the weird position of the lever cap: I didn't bother to update the CAD model as I moved some of the clamping parts around. On the real plane it clamps where you'd expect: on the flat bit of the cap iron (which is shown in blue).
The pale blue arrow shows the cutting angle: 36°. That's a lot lower than a Stanley #4 (45°) but is about the same as what you'd get with a low angle bevel-up plane with a 12° bed and 24° bevel. That low cutting angle is great for slicing easily through end grain or nicely grained wood, but not great if the grain's a bit more wavy as it'll cause tear-out very easily.
As I mentioned before, the mouth opening is quite tight. You can, of course, increase the cutting angle and the mouth opening together by adding a back-bevel onto the blade (shown in red):
Here the lever cap position looks even worse but that's just a CAD model issue as before. With this 10° back bevel the cutting angle is now 46° so fairly similar to a Stanley #5. The mouth opening is much bigger as a result of the back bevel so now the plane can be used to take quite heavy cuts if required:
That's fine when you're trying to rough some material down to thickness, but having a big mouth opening is perhaps not ideal for a smoothing plane. If we go back to the plain blade (with no back bevel and hence a 36° cutting angle) and try to plane something less well behaved (in this case Ash) you get a rough surface finish, which is hopefully visible in this photo:
So what if you want to have a tight mouth opening but a high cutting angle? That's where the unusual cap iron helps. This is what the plane looks like without the lever cap fitted:
That little protrusion on the cap iron (the nut for the screw that holds it to the blade) has the same diameter and thickness as the head of the screw. That, combined with the fact that the cap iron is flat and the same thickness as the blade, means you can turn them over:
It's now a bevel-up plane with a 66° cutting angle:
Having the cap iron the same thickness as the blade means that the tip of the blade is still in the same place and hence the mouth opening is the same.
Here's that same bit of ash after planing it with the plane in bevel-up mode.
Of course, in practice it's much more sensible to grab a different plane rather than removing the blade, turning it over and refitting it, so I don't know how often I'll take advantage of the the different ways of using it. Nevertheless it's been a fun experiment and I've really enjoyed the project. Even if the plane spends the rest of its life as a simple bevel-up smoothing plane it's great to try different things and see how they work.