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Tools and Stone cutting Version 19.09.2004 Daniel Mettler Laubeggstrasse 6 3013 Bern Switzerland +41(0)31 332 27 74 +41(0)79 565 68 08 [email protected] Urs Lippert Mettenbach 4934 Madiswil Switzerland +41(0)62 965 46 26 +41(0)78 621 73 70 [email protected] © 2004 +41/55/246'34'55 Gerhard Stoll +41/78/761'38'18 Trockenmaurer / Dipl. Arch. ETH/SIA [email protected] Hüeblistrasse 28 www.stonewalls.ch 8636 Wald / Switzerland www.trockensteinmaurer-verband.ch 1. How the type of rock influ- Working stone we differentiate bedded rock and amorphous rock. The ease of working ences stone cutting and the splitting characteristics differ greatly between bedded and amorphous rock. The grade of bedding determins the tools to use and the technique to adopt. (cf. fig. 1). A good bedding is caused mostly trough binder/ bondstone a planar inner structure of the rock. Planar textures can originate from different geologic prcoesses, however mostly strecher flat and thin stone bed-like jointing, foliated structure or chasms are responsible for it. Important for the working and splitting of stone is that the planar textures are the weak figure 1: spots of the rock. Hence when we have bedded and cyclopic to work stones we should always try to irregular stone cyclopical stone stone forms make use of these defects. We can de- tect this planar texture by noticing diffe- rences in grain size of the mineral constituents, troough a distinct bedded structure or noticable fine joints which point to chasms. Mineral veins are always a certain indication of chasms. Often chasms are so distinct taht the building stones by nature have good building surfaces which barely have to be worked. When the used rock lacks a planar texture the rock tends to take a cyclopic form. Mostly these are bulky rocks which are characterized trough a uneven structure and a homoge- nous distribution of the constituent minerals. Granite and volcanic rocks for example are rocks which tend to form cyclopical pieces. If chasms are absent is is difficult to cut these stones to a bedded form. A further important property is the degree of hardness. Quartzite, hard sandstones and other compacted finegrained rocks can be split easily. A further advantage that hard stones tend to be resistant against weathering. The cleavage property of the rock are as important for the quarrying as it is for the cutting of the blocks. Besides the bedding also the arrangement, size and bond between the mineral grains and the humidity play an important role and and influence greatly the splitting characteristics of the stones. The cleavage property is systematized in - good (perfect) - good (easy) - distinct - moderate - poor - not cleavable Thus the following cleaving forms can be distingished: Training manual dry stone walling www.stonewalls.ch page 2 Tools and stone cutting Stone splits precisely with a flat surface All finegrained plutonic rocks, bei plattigen extrustive rocks, most marbles and some sandstones. figure 2.1: Stone splits with a slightly undulating surface All finegrained plutonic rocks, some sandstones and schists parallel to the bedding. figure 2.2: Stone splits with an irregular surface (breaks out) Finegrained vulcanites and magmatites, most limestones and dolomites. figure 2.3: Stone doesn't split Porous rocks (lava, volcanic tuff, most conclomerates and some sandstones) figure 2.4: Stone breaks up Badly consolidated sedimentary and loose clastic rocks. figure 2.5: Stone splits in right angle to the hitting direction Schists of all kind some gneiss rocks when hit against the bedding. figure 2.6: Training manual dry stone walling www.stonewalls.ch page 3 Tools and stone cutting 2. General considerations for The splitting and cutting of stone requires the use of special tools. Thea differ depending cutting stones on the type of rock to be worked. The cutting and splitting of stone is well described in lit- terature, it mainly treats the trade of the stone mason. The tradition of stone cutting re- aches back to the ancient cultures of Greece and Egypt. It is not easy to draw a border between art and mere craft as it is difficult to designate exactly the tools of the dry stone mason, the tools for the stone dresser. Depending on the demands of the client, techniques and tools choesen for the realization of an building differ. For traditional dry stone masonry one can say that historically only few tools were used. The indispensable tools consisted of a lump hammer, a sledgehammer and a crowbar. Chisels, machines and other equipment were only seldom used. The surfaces which eventually have to be worked are the top and bottom bed, the joints and the face (cf. fig. 3). The art of the dry stone mason consists in the skillful selection and matching of stones with a minimum of cutting. A trained eye, power of spatial imagi- nation and not to forget the experience play an equal important role as all the supporting machinery and tools. In the following are described the most important techniques and tools for splitting, cutting and lifting. figure 3: terminology 2.1 Technique of stone working When cutting stones the hardness of the rock to work plays an important role. Accordin- gly we choose different tools for the working of soft stones than when we work hard stones. The first step is the choosing of the stone to cut. It is important to judge the stones according to the following criteria: - visual criteria (color, structure, natural bedding, chasms, clefts, cracks, weak spots). - acoustical criteria: faulty stones sound vague, muted when striked with a hammer. 2.2 Splitting After selection, very big stones can be split with wedges. To do this holes are chiselled out or drilled along the line the stone is to be split. The distance between the holes and the size is dependent on the type of rock to be split. Today in Switzerland the holes are chiselled with a pneumatic hammer or a pneumatic / electrical drill. For stones the size used normally building dry stone walls the distance between the holes is about 10 - 15 cm and the diameter is normally 22 mm. It is best to pierce the whole stone to avoid a warped splitting surface. The stone is the split using wedges or plugs and feathers Training manual dry stone walling www.stonewalls.ch page 4 Tools and stone cutting figure 4, left: Drill holes in a distance of 5 - 15 cm. figure 5, right: A B A, splitting with a wedge, and B splitting with plugs and feathers "Plugs and feathers" are especially handy to split stones. The smallest size to get has a diameter of 22 mm and a lenght of about 10 cm. For the need of the dry stone mason this size is adequate. The three-pieced wedge is inserted in the drilled holes and alterna- tely hit with the lump hammer. It is very importandt to hit the plugs and feathers equally (noticeable trough the sound the plugs emit when hit) to get an even splitting. Splitting stones we differentiate between splitting with or against the bedding (cf. fig. 6 and 7). In most cases more wedges are needed when trying to split against the bedding. To get an even split it is best to pierce the stone fully when drilling holes for the plugs and feathers. figure 6, left: Splitting of a horizontal bedded rock figure 7, right: Splitting of a vertical bedded rock Besides drilling and splitting with wedges or plugs and feathers a simpler and time- saving technique can be used. It is mainly used when splitting parallel to the bedding and when shaping big but not too thick stones. It is the splitting with spalling sledge and sledgehammer. When cutting plates at right angles to the bedding one side of the stone is put on a scantling. Then the desired splitting plane is marked with the pointed side of the figure 8.1: spalling sledge on all faces of the stone. Then with ever stronger blows on the marked line the stone is hit until it splits. The sound of the stone emits when hit gives us information about the splitting process. When splitting parallel to the bedding even large stones can be split up in plates. Doing this it may be handy to work with two big hammers (and two masons): a figure 8.2: Training manual dry stone walling www.stonewalls.ch page 5 Tools and stone cutting spalling sledge and a sledgehammer. The spalling sledge is put on the stone like a pitching chisel. The sledgehammer is used to hit the spalling sledge. figure 8.3: figure 9.1, left: figure 9.2, right: figure 10.1, left: figure 10.2, right: 2.3 The cutting When the big blocks are split up the blocks are roughly shaped. At first the protruding points on the bedding faces and the joints are cut off so that the stone fits roughly the neighbouring stones. Once for this rough work mainly sledgehammer and mason's hammer were used. Today we use also chisels, pneumatic and electric machines. The bedding faces and the joints are then prepared to fit as close as possible the top bed surfaces of the adjacent faces. The surface touching the adjacent stones should be as big as possible and lay as near the face as possible. The tools used to do this joint figure 11: are mainly the punc and tracer. schematic sketch (sec- tion view) of the surfaces to be worked (hat- bottom bed ched).

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