Wooden Planes #3: The Mouse

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I wanted plane #3 to be another block plane, but I wanted it to be a different kind of block. By this point, I’d done a lot of reading about planes in general and plane-making, and some of it was starting to sink in. Low angle, bevel-up planes sounded like a good thing because of the versatility, so I hit on the idea of making one from wood.

The Internet is a wonderful resource for finding information on just about any conceivable topic. Usually, there is too much information, requiring you to sift through dozens, hundreds or even thousands of pages and decide what is good and what is not. Wooden low angle bevel-up hand planes, however, is one of those few topics for which very little information is available. There is some, yes, but most of what I found related to the problems to be encountered in trying to build one and get it to function well.

And yes, there are problems. First, the mouth opening. On a bevel-down plane, the cutting edge of the iron touches the wood somewhat ahead of the front of the bed. It depends on the thickness of the iron and the bed angle, but at 45 degrees and using decently thick iron like a Hock or the LV, the iron hits about 1/4” ahead of the bed. Add a small opening ahead of the iron, and you have a total mouth of a bit over 1/4”.

Why is this important? The standard practice is to glue up the pieces so that you start with a smaller than desired mouth opening and then open it up using some kind of tool. A float, a file, or perhaps some kind of sanding board. Obviously, the tool has to be narrow enough to fit into the small mouth opening, but still function well enough to accurately remove wood. For a bevel-down plane, it is easy to make a sanding board that is exactly the thickness necessary width using 1/8” MDF and sandpaper.

For a bevel-up plane, the cutting edge of the iron hits immediately in front of the bed, and in order to get a fine mouth opening of, say, 1/32”, you need to have some way of gluing it up so that there is a finer opening, and then find a very thin tool to fit into that very thin opening and still be able to remove wood.

The second problem is that of a relatively thin bed. Typically, a low-angle plane has a bed of 12 degrees. A wedge of wood 3 1/2” long and tapering at 12 degrees is only 3/4” thick at its thickest. That’s not particularly strong.

And there is a lot of pressure on the bed at the point immediately behind the cutting edge of the iron. Precisely where the bed tapers to a thin point. This makes the bed susceptible to cracking or chipping.

The third problem is created by requiring a fairly large opening in the body to accommodate space for the iron, wedge, pin assembly and clearance for shavings to escape. On a bevel-down plane, this opening is typically 60 to 70 degrees of arc. On a bevel-up, the opening would need to be larger, a minimum of 80 degrees, if only to allow a line of sight to the tip of the iron from directly above the plane. A larger opening means weaker cheeks on the plane.

Thinking through all of this, I came up with a design. First, build the plane seriously overlong in the front, and with zero mouth opening. After glue up, use my jointer to take down the sole until the mouth opening appears, and then cut off the unnecessary length in front. Second, build a small flat into the front of the bed, about 1/16”, so that the bed doesn’t actually taper to a point. Third, forgo the pin assembly arrangement, and glue in a piece – I won’t call it “ears” – for the wedge to act against.

The plane is wenge and purpleheart, with paste wax as a finish. It works quite well, and I’ve successfully used it with blade angles of 25 degrees to 50 degrees, for effective cutting angles of 37 to 62 degrees. Simply swap out the iron (or regrind), and it becomes a plane for a different use.

Despite my concern with structural integrity, it is solid. That is partially due to using two strong, hard woods, and (I’m pretty sure) partially due to the inner piece the wedge jams against.

It isn’t perfect, of course. There are two primary issues which prevents it from being my daily user. First, it is too wide to be comfortable for single-hand use for any length of time. I used the LV wooden plane iron, and the narrowest available is 1 7/8” wide. Add to that the cheeks and clearance spacing around the iron, and the plane is about 2 1/2” total width. For someone with large hands, that might be OK, but something closer to 2 1/4” would be more comfortable for me.

The second flaw is that the bed slipped slightly during the glue-up and I didn’t notice. As a result, the iron sits at a slight angle to the cut. There isn’t enough clearance around the iron to skew it to compensate, so the cut ends up being uneven. I suppose I could grind an iron with a slight skew to match bed and solve the problem.

I tend to pull this plane out when making chamfers. The slight skew doesn’t matter, and the plane works well with a two-handed grip using knuckles as fences.

I might make another of these, but build it for a narrower iron. Ron Hock sells a 1 1/2” by 4 1/2” iron which would be just about perfect.

Source: LumberJocks.com

Wooden Planes #3: The Mouse