The Coffin Plane Gets its New Mouth – 2.


Following onwards from the last posting about a new mouth arrangement on my old coffin planes, This is where we start marking out and cutting. Where wooden planes were concerned, this was a standard repair for these tools; whilst a good quality job was essential and expected, a re-mouthed plane was not a sign of an inferior tool or one that was past its best. Compare it to a well-made pair of shoes that can be soled and heeled occasionally and will last for many years.

British wooden bench planes followed a basic pattern for centuries. Some are still made to a traditional pattern and not much has changed. Blocks of Beech plane blanks were prepared from a riven section of a log. The blanks resembled slices from a cake in section. Next, they were air-dried for several years – before kilns were available to accelerate the process.  When dried, these blanks were selected for straightness, even density and uniformity of the grain along their length.

The orientation of the finished plane was important. The blank would start as a wedge shape riven from the log, then be trimmed in size to resemble the shape of the plane. When viewed from the end, the grain pattern would show slightly curving annual growth rings from side to side. When work began on making the plane, it was customary to orientate the oldest growth rings near the top, the youngest at the sole. As ever, there may be exceptions to this, but all my planes show this pattern.

Next, the shape of the finished plane would be marked so that the run of the grain pattern along the length of the plane contained a slight tilt, running from the toe end, downwards to the heel. The angle of the tilt is only a couple of degrees off the horizontal but is intended to present end fibres on the sole instead of parallel long grain. The sole of the plane is constantly in moving contact with the work so these end-fibres inhibit wear, are less likely to change shape due to seasonal humidity changes and promote the absorption of linseed oil. Linseed oil nourished the wood, was used to ensure that the body of the plane gained weight due to its absorption and was able to be self lubricating to a certain extent in use.

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The angled grain can be seen in this sideways view of the plane. The toe is to the right, the heel at the left.  To see the downward direction of grain, look at the light coloured lines flowing downwards from right to left, in the picture, toe to heel. The annual lines of growth can be seen slanting downwards from the toe, but there’s only a degree or two of tilt in it.

(This is why, when re-flattening a plane sole with a scraper blade or something similar, it is essential to take straight, even strokes from the toe toward the heel – never the reverse, as you will be scraping against the grain)

This slanted grain is most common in shorter planes like this 8 inch coffin. Becoming less obvious and prevalent in longer wooden planes – Jacks or Fore-Planes, Jointers and the like – where long sections of stock that is straight enough to provide a uniform tilt along the full billet may be at a premium. As with everything else, some material was better than others and so was the skill of certain makers. This would have been reflected in the original cost of the plane.

When the patch is inserted I intend to cut my inserted piece on a slight tilt to preserve this tilting grain feature.

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To begin with, although the size and shape of the infill is not crucial, its rear line needs to be parallel to the edge of the blade is and it is important to mark where this notional line needs to be as I won’t be able to gauge it from the blade later when everything is inserted and glued in. To do this, the blade needs to be in its cutting position, protruding very slightly and level with the sole. Push a straight edge against the edge and hold it while marking the line of the blade on the edges of the cheeks each side. It is this line that I shall work to when cutting the infill to size.

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Working from the width of the mouth I mark a line on a piece of stiff card that will form the template for the infill. This is shown as ‘A’ in the sketch and needs to be equal to the exact width of the mouth. It’s the only one that is critical, I then mark a ‘keystone’ shape to conveniently and symmetrically fit inside the sole of the plane.

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The card template is cut and I now need to slice a couple of blanks out of some scrap Beech that I know is bone-dry. These need to be no more than 1/4″ (approx 5 – 6 mm) thick. I’ll mark the blanks from the card and use them to eventually mark the sole of the plane.

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When I’m making the blanks from the piece of scrap, I intend to cut a couple of inserts at the same time, because I have two planes to re-mouth.

An initial downwards cut with a cross-cut saw defines the size of the blank. Next I shave  the face sideways and finish with this cabinet-makers float. It is deliberately at an angle to the surface as, you will recall I want end grain presented on the sole of the plane. One side is finished flat and clean, as this will be the face of the blank that is glued face-down into the body of the plane so that it will mate onto the excavated part of the sole. This new float from Noel Liogier is ideal for this.

Next, I’m going to orientate the face of the blank at a slight angle, again only a couple of degrees, in order to present this end grain on the face of the sole at about the same angle as the inherent slope in the plane body.

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Cutting downwards with a rip saw.

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Two blanks, about 1/4″  (6mm) thick; it is crucial at this stage to identify the direction of the downward grain, so that they can go into the sole with the grain running downwards in the right direction. Mark the inward facing edge and the slope of the grain when it is freshly cut because it is very difficult, almost impossible, to work out later.

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Here’s the first part of the shaping process – I need to get the front edge square. I’m using the previously flattened face (at the rear) to guide the edge plane.

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I’ve cut the ‘keystone’ shape from the template – slightly over-sized – as it will be trimmed to suit later.It is important to get the sides squared off and clean cut. The only line that I don’t bother with at this stage is the long base line (‘A’ in the diagram), as this will be trimmed to the exact size when it is in place in the plane, using the line I scribed earlier. Then the blade is presented to it for a final fit.

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Marking the plane sole is next. I find that it is easiest to lay a piece of wide masking-tape above the throat in order to mark it out with a pencil. I can then see where the infill piece needs to sit and mark it ready for the process where I start to cut with a chisel.

…………… and that will be the focus of the next and final part.

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2 comments
  1. george said:

    this is top stuff,thx

  2. That is a great tutorial. Looking forward to part 2.

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