Friday, 6 July 2018

The medieval toolchest: the plane (part 6)

I thought that the medieval plane history was more or less complete in the five and a half previous posts. I was wrong, a book on archaeology in Schleswig-Holstein (Germany) did contain two medieval planes dating from the 11/12th century that were unlike any other medieval planes.

The wedgeless plane



The 1:3 photo from the archaeology book 'Ausgrabungen in Schleswig. Berichte und Studien 17'. The middle photo has a length of 63.6 mm in the book, meaning an actual plane length of 19.1 cm. Archeologisches Landesmuseum Schleswig, Inv. nr. KSD 389.014.

The plane from the Hafenstrasse 13 in Schleswig was found in 1982 during an excavation. It dates from the 12th century and made in out of one piece of Taxus. The front handle or toat is carved in the form of a male figurehead, while the complete plane has a more ship-like form. What is most unusual of this plane is that the plane blade is not secured by a wedge (against a pin or cheeks). Instead, the plane iron has a trapezoid form and secures itself in a groove that also becomes smaller at the top. So far no other plane is known that uses this method of securing the iron. The probable reason that this is the sole plane is obvious, this method is quite impractical.

Nevertheless, it was interesting for us to construct a replica of this plane and try it out. Although the article in the archaeology book also described a reconstruction of this plane, not everything was covered and we needed to find out much ourselves. We were lucky to have a large felled taxus tree available for our replica - thanks to castle Hernen.  From this a suitable block of wood was sawn, on which the plane was drawn. First, it was necessary to enlarge the image from the book (1:3) to its 100% size. This was a bit complicated as the three photos (top, bottom and side) did not have the same size and I had to adjust it with help of a photo program on the computer. Also, there were no front and back images available, nor a cross-cut drawing. The images were printed and cut-out with a scissor and used to transfer the plane drawing to the wood.

The Taxus block with the plane drawing.

First, the ship-from was drawn on the sides of the block. These were then cut out with a bandsaw. The top part was then glued back on with a piece of newspaper in between, so it could be easily broken of again. Then a drawing was made on the underside of the plane and also sawn by the bandsaw. Because the top part was glued back, it could function as a stable basis for sawing. After sawing, the top part was broken away.

Left: the top part glued back on with a newspaper in between. This way I could stable saw it when upside down. Right: the top part broken away again when the oval ship shape had been sawn.

Then the figurehead was carved with help of gouges and a carving knife. The hairs were filed. Finally, the figurehead was sanded and waxed. The remainder of the plane was not yet carved, as the space between the opening for the iron and the rim is rather small. My thought was that this was safer to do after the making the groove for the plane blade.

Some of the stages of carving the head. The plane was clamped in a vise, with a piece of wood to rest the head on. 

The author had measured the size of the plane iron with help of a paper mould. It was found that the iron had a thickness of 3 mm, a length of 65 mm, a width of the cutting edge of 42 mm and a top width of 25 mm. I did have a top part of a plane blade (the bottom part being used by another medieval plane) which was cut and sanded to the correct size. It appeared later that my choice of the blade was not very wisely made, as the top consisted of soft iron that was easily blunted by adding the iron to the plane and its following use.

My plane iron has a bottom width of 48 mm and a width of 46.6 mm at the point it leaves the plane. 
Top width is 26.6 mm. It has a total length of 63 mm. The blade was sharpened with a 30 degrees bevel.

I measured the angle for the iron using the top and bottom openings and found it to be 45 degrees - an angle comparable to that of modern planes. The description of the plane in the book mentioned an angle of 43 degrees. The hole for the blade was drilled out, but first a piece of wood was cut out with a chisel  so that the drill bit could do its work on a relatively horizontal surface. After drilling that the hole was cleared and enlarged by hand.

The power drill set-up, with the platform set at a 43 degree angle. A piece was cut out with a chisel to have a horizontal surface for the 6.5 mm drill bit.

The opening was cleared and widened with a chisel.

After that the groove for the plane iron needed to be made and fitted to the size of the iron. The basic groove was cut with a keyhole saw, which had a thick blade (slightly thinner than the plane iron) and could pass through the hole. Then the groove was carefully widened and enlarged, so it fitted the iron with help of a 2 mm mortise chisel and a 3 mm standard chisel. When the iron almost fitted, the remaining carving, sanding and waxing of the plane body was done. Then the iron was 'fixed' by placing the plane on a piece of soft wood and hitting it with a hammer at the top end.

The groove was sawn using a -bladed keyhole saw.

Carefully checking how the iron fits, each time the groove is widened a little bit.


The plane with and without the plane iron.

Also the top side and the underside of the tail are angled.

The plane has a comfortable grip and is easily pushed on a piece of hard or softwood. At the moment the blade is a bit dented (for reasons mentioned above) and set to produce very thin shavings. The latter is one of the drawbacks of this plane design: it can only be set at one specific depth. Perhaps you can adjust it by adding a thin strip of wood or paper into the groove; I have not tried this. Furthermore, if you need to sharpen the blade - thus making it 'shorter', you also need to plane a bit from the sole of this plane.

Side view of the plane. The basic body of the plane is only 28 mm high. The total length is just less than 20 cm.

The router plane

The 1:3 drawing from the archaeology book 'Ausgrabungen in Schleswig. Berichte und Studien 17'. The top drawing has a length of 53.1 mm in the book, meaning an actual length of 15.9 cm for this plane part. Archeologisches Landesmuseum Schleswig, Inv. Nr. KSD 382.011.

The second plane from Schleswig dates from the 11th/12th century and was excavated from the Plessenstrasse 83/3 in 1976. This plane was made from maple. Although only half the plane remains, its function was clear due to the iron nail holing a remnant of the wedge. The opening for the iron is large, and the wooden sides are relatively thick, which makes it likely that this plane functioned as a router plane. Also interesting is the decoration with a head of a duck at the end  of the plane. Also the reconstruction of this plane was described in the article by Karl-Heinz Gloy. We did not make this plane (yet). He estimated that the plane had a length of 23 cm, considering that the opening for the blade was in the middle of the plane. The opening for the blade was set at 3 cm; it has a width of 1.7 cm. The angle of the opening is 40 degrees. The length and width of the reconstructed blade were 75 and 15 mm, respectively, with a sharpening angle of 30 degrees. 

Sources

  • H.E. Saggau, 2006. Gehauene und geschnitzte Holzfunde aus dem mittelalterlichen Schleswig. In: Holzfunde aus dem mittelalterlichen Schleswig. Ausgrabungen in Schleswig. Berichte und Studien 17. Wachholtz verlag, Neumünster, Germany, pp. 199-304.
  • K.-H. Gloy, 2006. Ein Bohrer und zwei Hobel aus dem mittelealterlichen Schleswig. In: Holzfunde aus dem mittelalterlichen Schleswig. Ausgrabungen in Schleswig. Berichte und Studien 17. Wachholtz verlag, Neumünster, Germany, pp.305-310.

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