Optimising the cutting tool geometries can reduce waste while increasing timber yield. The industry is moving towards thin-kerf bandsawing of timber, and therefore, the geometry of the minor cutting edge and minor first flanks of cutting teeth become more important. Six cutting teeth with varying minor cutting edge angles (0°, 2°, 4°, 6°) and minor cutting edge clearance angles (2°, 4°, 6°) were tested by cutting into the heartwood and sapwood of frozen and non-frozen Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.). Single cutting tooth tests were conducted, and the cutting and feeding forces were measured. The cutting forces were higher for Scots pine due to its higher density. Frozen sapwood resulted in higher cutting forces. The feeding force of frozen sapwood stood out as it was highly negative (i.e. self-feeding) compared to frozen heartwood, non-frozen heartwood and non-frozen sapwood. An increase in the minor cutting edge angle and minor cutting edge clearance angles, and therefore more room for elastic spring-back, can lead to up to less friction and 40% lower cutting forces. Higher minor cutting edge angles and minor cutting edge clearance angles resulted in less-negative feeding forces (i.e. less self-feeding) for frozen sapwood but remained relatively unchanged for the other wood conditions.

As the sawmill industry is moving towards thinner bandsaws for higher yields, it is important to study the cutting force in more detail. The cutting force can be split into two zones. Zone I concerns the force on the major cutting edge as well as the friction force on the major first flank. Zone II considers the forces on the minor cutting edges as well as the friction forces on the minor first flanks. Zone II cutting can significantly affect the cutting force and has not been studied in great detail. Frozen, non-frozen and dry heartwood of Norway spruce and Scots pine were cut using different tooth geometries and the cutting force was measured. The major cutting edge, clearance, band thickness, minor cutting edge angle and minor cutting edge clearance angle were investigated. The y-intercept of the cutting force–width graph was used as the Zone II force (at this point the Zone I forces are assumed to be zero). The Zone II force contribution to the cutting force was studied. The results show that frozen wood has less elastic spring-back and therefore less Zone II cutting. Dried wood showed a significantly higher degree of Zone II cutting (55−75% contribution to the cutting force). Changing the major cutting edge from 2.87 mm to 1.6 mm resulted in 10–15% higher Zone II force contributions.

For economic and environmental benefits, sawmills can reduce their waste by sawing with thinner bandsaw blades. When altering the cutting tooth geometry, it is vital to monitor the sawing process in realistic wood conditions such as frozen (green), non-frozen (green) and dried. The fundamental way to monitor the sawing process is to analyse the cutting forces when single cutting teeth interact with the wood. The three cutting forces acting on a sawtooth are the main, normal, and lateral forces. The main force can be split into two: 1) cutting by the main edge and 2) cutting by the side edges (the side force). The objective of this thesis work was to examine the main, side and normal forces in different wood conditions while cutting with different tooth geometries. In sawing, it is desired for the main and side forces to be minimised, and the normal force should remain close to zero. Two abundant Scandinavian wood species were considered: Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.) in non-frozen, frozen and dried conditions. The heartwood and sapwood were tested separately for non-frozen and frozen wood. The altered tooth geometries were the cutting width, clearance, band thickness, and the radial and tangential clearance angles.The main force was approximately 75% lower for the narrowest cutting tooth of 1.6 mm compared to the reference 2.87 mm wide tooth used in the industry. Narrow cutting teeth could, however, result in faster tool wear and vibrations. The main force was higher in pine than spruce due to the higher density of pine. Frozen sapwood showed distinctly higher main forces. The radial and tangential clearance angles had a negligible effect on the main force. There was a slight reduction in the main force in frozen sapwood at high radial and tangential clearance angles of 6◦. In frozen sapwood, the normal force was highly negative and self-feeding was observed. The normal force was less negative for narrower cutting teeth and at high radial and tangential clearance angles of 6◦. The cutting width, clearance and radial and tangential clearance angles did not have a notable effect on the normal forces in the remaining wood conditions, and the forces remained close to zero. The elastic spring-back plays an important role in side cutting and can be as high as 4 mm. Frozen wood has less elastic spring-back and, therefore, less side cutting. The percentage of side cutting to the main force was between 55% - 75% for dried wood. Lower clearance and lower radial and tangential clearance angles resulted in more side cutting due to increased contact between the teeth and elastic spring-back.The results show that special consideration needs to be taken when sawing frozen sapwood in the winter. Furthermore, the side cutting force plays a larger role when the cutting width is reduced and in dried wood and needs to be studied in more detail to understand its impact on the cutting process better.v

Reducing the kerf width in bandsawing has potential in reducing waste while optimising the yield. To be able to reduce the kerf width, understanding the cutting forces becomes critical. In this work, nine cutting teeth with varying band-body thicknesses and side clearances were tested by cutting both heartwood and sapwood of Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.) in frozen and non-frozen conditions. Single cutting teeth were moved into rotating wood samples in the 90–90° cutting direction, with chip thicknesses of 0.9 mm per cut. The main and normal cutting forces were measured. Scots pine had a higher density than Norway spruce and, therefore, a higher main cutting force. Non-frozen sapwood, non-frozen heartwood and frozen heartwood resulted in similar main cutting forces, but frozen sapwood resulted in significantly higher main cutting forces. Reducing the cutting width by about 45% resulted in an approximately 40% reduction in the main cutting force. The normal forces were not significantly affected by the species or cutting width. Frozen heartwood, non-frozen heartwood and non-frozen sapwood had similar normal cutting forces. Frozen sapwood had negative normal forces, and thus self-feeding was observed.