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Wood which is relatively easy to work is used for carving. This calls for a wood moisture contents of 8 % to 10 %. Drying of wood in the trunk (log) results in many drying cracks which heavily limit the use of the wood or even make it useless. The logs must be prepared first before the drying process can start. For this purpose the logs are cut on machines in sawmills as many times as necessary or they are manually split up. The basic shape of all splitting tools is the shape of a double-sided wedge which effects the chip less cutting of the wood.
Figure 1 Double-sided wedge
1 beating force or pressure (F), b angle of wedge
The axe is used for splitting of thin round timbers and for rough chiselling-off of wooden objects.
Figure 2 Axe
1 blade, 2 handle, 3 cutting edge, 4 bevel, 5 blade head, 6 wooden key or steel key
The handle should have a length of approx. 600 mm and be firmly secured (keyed) in the blade head. The cutting edge has the shape of a double-sided wedge with an angle of wedge of 25 degrees and must always be kept sharp.
Figure 3 Angle of wedge of the axe
cutting edge
For splitting of shorter and longer logs, steel or hardwood wedges are used which are driven into the wood by a sledge hammer.
Figure 4 Hardwood and steel wedges
bH hardwood wedge angle = 25 degrees
bS steel wedge angle = 15 degrees
The slenderness ratio (angle of wedge) is important for the shape of the wedges.
What components does an axe consist of?
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Different types of carving knives and carving chisels are used as carving tools. The carving knives are provided with a ground double-sided taper and consequently with the shape of a double-sided wedge with a very small angle of wedge.
Figure 5 Carving knife
1 blade, 2 handle, 3 spike, 4 bit, 5 cutting edge
The carving knife is held and guided by one hand and predominantly used to produce smaller objects which can be carved in the hand with no need for clamping devices. The carving chisels are provided with a ground single-sided taper and consequently with the shape of a single-sided wedge. Therefore, their mode of action is similar to that of firmer chisels and mortise chisels.
Figure 6 Carving chisel (sculptor's
chisel)
1 cutter, 2 handle, 3 spike, 4 bit, 5 cutting edge, 6 bevel
The carving chisels, also called sculptor's chisel, are guided by hand or beaten by a wooden cudgel (mortise cudgel).
Carving chisels are produced in a great variety of shapes and sizes and thus can be used for any types of carving operations.
Table 1:
Carving chisels (sculptor's chisels)
|
Designation |
Features |
Application |
|
Straight chisels for different cuts |
Square, angular or round main cutting edge |
Carving of recesses of different types |
|
Bent chisels |
Chisels are bent or offset in their longitudinal axis |
Carving of hidden recesses |
Figure 7-1 Carving chisels: straight
chisels for different cuts
Figure 7-2 Carving chisels: bent
chisels
Why must a carving chisel, which is beaten by a wooden cudgel, have a metal ring at the upper handle?
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Maintenance of carving tools comprises:
- attendance and cleaning of the tools,
- checking and, if necessary, replacement of the handle,
- sharpening of the cutting edges of the tools.
The general attendance of carving tools is similar to that of other chip-producing tools.
Sharpening of splitting and carving tools, however, features some peculiarities which are explained in the following.
Sharpening of splitting tools
Splitting tools are sharpened by grinding. The axe is ground to the specified wedge shape by rotating grindstones or emery wheels with the cutting edge to be held against the direction of rotation of the grinding tool. The burr produced is removed by alternately stoning the two bevels of the cutting edge with circulating movements of a wetted oilstone.
Steel wedges are not ground nor stoned. By beating with the sledge hammer, burr maybe produced at the rear side of the wedges which is to be removed by grinding.
Attention: Burr particles of the wedge may split off when the wedge is driven in and cause injuries!
Wooden wedges are used until they split up or break, and then they are replaced.
Sharpening of carving tools
Carving tools are also sharpened by grinding.
Grinding and stoning of carving knives and carving chisels requires great care and a lot of experience. Trainees should not sharpen carving tools until they master the sharpening process of simple wood-working tools.
Because of the great variety of shapes of the carving chisel cutting edges, each tool is to be treated differently.
Grinding is similar to grinding of planing tools or fimer and mortise chisels. With round chisels, guidance by hand is to be steady, smooth and with little pressure. Constant cooling is required during grinding to avoid annealing.
Grinding is to be done carefully to prevent excessive abrasion!
For stoning of the cutting edges (removal of burrs), different oilstones are to be used, the cross-sectional shape of which must correspond to the shape of the cutting edge.
Figure 8 Cross sections of oilstones
1 square, 3 triangular, 3 round, 4 half-round, 5 wedge-shaped
The reciprocating movement of the tool on the oilstone or vice versa is continued until the burr is removed and the cutting edge has a bright appearance.
Carving tools are generally to be stored so as to prevent them from rusting and hitting of hard objects.
When the tools are not used, the best way of storing them is in a suspension device in a wall chest.
During carving the tools should be orderly arranged side by side on the workbench with the cutting edge showing towards the trainees.
Which tools are used for sharpening of carving chisels?
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