Shaped planes, part V

My previous expenience with moldings disclosed that my hollower is not satisfactory. The plane chatters. This may be due to saveral reasons. The most likely is that the plane blade s not thick enough. So, sucker for punishment that I am, I decided to make a thicker blade. Double sucker that I am, I decided to use a different style, based on a picture in David Fink's book, Making and Mastering Wooden Planes (q.g.). Glad I did. I have learned a lot.

This style of plane is a lot more like the traditional wooden shaped planes.
Here you can see the overall scheme. We have a block of wood 145mm by 20mm thick by about 50mm wide. The bottom of the plane has been shaped to a 10mm radius curve, by guess and by gosh. In the block a mortise has been cut. Into this mortise will fit a blade. The blade for now is just roughed out. The mortise has two angles. The one on the left is critical. It is the bedding angle for the plane. The traditional angle for bedding is 45 deg and this is what I use, standard pitch. However for hardwoods you might want to use a steeper angle, like 57 deg which as I recall is called York pitch. These are traditional pitches, and assume the blade of the plane will be sharpened at 25 deg. If you do not sharpen the blade at that angle you will have some math to do. It is all about angle of attack. I recommend reading Garret Hack's The Plane Book, q.g.

It took me some time and a few trips to the 'net to figure out what the plane blade looked like. Mr Fink did not tell me. But eventually I figured it out. The roughed-out blade is shown on top of the plane. I cut it out from a piece of worn-out circular saw blade. This is almost 2mm thick. Approximately twice as thick as the old ripsaw-derived blade on my previous incarnation. I like this a lot. The thicker the blade the less the chatter.

The place where the blade goes in a not-so simple mortise. Leftmost is the ramp where the blade will go. I will call this the blade ramp. It is 45 deg, the bedding angle. If you go make one of these things, under no circumstances can you touch this blade ramp! At right is another ramp. It is traditional to cut this at 62 deg but I cut it at 60. Easier, (with a 30-60-90 square), to lay out and the exact angle does not matter; cut your wedge to suit. This ramp has two functions. One, it holds a wedge to keep the blade in place. So I will call it the wedge ramp. Two, you can see I can slide my 30-60-90 square along the plane towards the front (right in the pic) any amount I want. The amount I slide it towars the front will determine the throat opening. Planes are very fussy about throat openings. My rulae of thumb is that the throat opening should be about the width of the shaving you want to take. So my current strategy is as follows. The wedge ramp should be the thickness of the blade ahead of the place where the blade ramp comes out. The goal is for a zero throat width. I can take wood off. I can only put it back with great difficulty. In fact, only with Plastic Wood (tm).

So when we have fiddled with this a bit, we can get a decent fit.
A decent fit to me means that the blade will fit exactly flush with the bottom of the plane with zero overhang. So the throat opening is zero. That is what I want. To get away with this we have to look at the other side of the plane.
There is a blade-ramp shaped cutout on the other side of the plane. It hasto be deep enough to take the plane blade all the way down, until it is flush with the bottom. Took some doing.

My next post, part VI I suppose, on the subject will tell you about my adventures in throat-cutting. Fortunately, human life is safe. The only throat I intend to cut is that on the hollower plane. I must also relate my learnings on ramp-cutting. And there is yet the chip-escape hole to drill. So much to post, so little time.

Shaped planes, Part IV

After I did my last post, I reflected that the video I recommended goes by at warp factor five. Very fast. So I have decided to go step by step. This is my second practice molding. So we start with a scrap piece of wood left over from John's projects. We clamp it in the vise, and draw a picture on the end of the sort of molding we want. I have made this one up from scratch, but it sort of resembles the molding I cut in the previous post.
Now before you do anything else, flip the piece over in the vise and in the bottom of the piece, cut a rabbet. The purpose of the rabbet is to hold your painting. Here I am using the micro Veritas rabbet plane to do so. It cuts about a 6mm rabbet. About right. I have clamped a steel ruler onto the scrap piece of wood, AKA "stock" to guide the rabbet plane. If you don't do this your plane will wander. You will be upset. You will ruin your piece. Something thicker than a steel ruler would be better, because it will force you to hold the plane square to the work. I will call the tiny plane Peanut in what follows. When you plane a rabbet this small you spend as much time clearing shavings as you do planing. They clog up the tiny hole in the plane. But you do it. Now flip the piece over.
You can see the rabbet or rebate you have just cut, underneath at left. Now what we want to do is rough out the profile with rabbet planes. A rabbet plane cuts far faster than a shaped plane. A plow plane would cut even better. But this piece is about 20 cm long and the plow will not track properly. If I can, I use Big Daddy. This is the macro sized Veritas rabbet plane. He cuts big time. A joy to use. And he does not clog up.
Now, what are we trying to do? We have a continous curve in the profile. We obviously have to remove some wood to get there. Differing amounts of wood, depending on where you are in the profile. So we are trying to approximate the curve by staircase steps. Engineers call this a step function approximation. So I cut rabbets, guided by fences, until I come to the point where I cannot clamp the fence any more -- too irregular a profile. Forget about cutting rabbets freehand. Superman can do it. Most of us can't. At this point our molding looks like this:

I cheated a bit and used a flat plane (violin maker's plane in fact) to get a slope in the part to the right. But you can see the stair steps. Now we are ready to hollow out the big curve at the right. Break out your hollower.
Now plane out the hollow. Do not be too fanatic about your drawn profile. Your hollower has a fixed radius (10mm in my case) and your eyeball had another. Look at the thing. Does it look okay? Stop. Do not be afraid to hold the hollower at an angle, as I am doing in the above pic. Sometimes it cuts better that way. I have a lot to learn still. The rabbets you cut guided the hollower. Superman excepted, you need a guide for a shaped plane; the rabbet (or groove) provides it. So you cut straight and do not wander.

We have dug a lovely curved trench in our profile. Here it is:

It does not quite match the drawn profile. Of course it doesen't! One drew the profile by eye. The hollower has a fixed 10 mm radius. Miracle if they matched. Do not be concerned too much by this mismatch. It still looks nice and that's what matters. Now let's do something about the hills, having done the valleys. We break out the rounder plane. This has exactly the opposite curvature as the hollowers. All I have at this point is 10mm radius. The rounder looks identical to the hollower. (except for the bottom). It is a bear to sharpen. After I applied it I had something like this.

Needs some more work but is recognizable as a molding or picture frame. It was at this point that I realized that this business is just like carving. You are limited in carving by the sweep of your gouges, i.e. curvature. You are limited in in moldings by the radius of your plane. Sigh. It looks like I am into a whole new era of plane-making. Need some much narrower radiuses, say 5mm. To start. If I were in 14th century Florence I would have gone to Giuseppe the plane-maker and ordered up a bunch of radii. The bill, no doubt, would have been paid by Cosimo de Medici, who wanted some frames for his pictures. But here I am in Alaska, got to do the whole megilla myself. Cosimo de Medici nowhere in sight.

I did a bit of cheating and applied a violin-maker's plane (commercial) to the thing and got a perfectly decent molding. We are not there yet, but we make progress.