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Sawmilling in Sweden

Wood Technology Department, Forest Products Research Laboratory, Stockholm

SWEDEN produces some 1.5 million standards of sawn wood annually, over 64 percent being of export grades, and Swedish timber is firmly established on world markets. This country's experience in sawmill organization and practices is therefore of general interest.1

1This article is a brief condensation of a much more detailed report compiled by Dr. Thunell in his capacity as chairman of an FAO working party on sawing and machining.

In Sweden, as elsewhere, the location of sawmills is determined by the facilities available for bringing logs from the forest and for transporting the sawn products to the market or shipping center. In the northern part of the country the large sawmills are usually situated near the coast, since logs can be conveniently floated down the rivers to the mills and the sawn products loaded almost directly onto ships. In southern and central Sweden, where most of the saw logs are transported by trucks, the sawmills tend to be located in the interior of the country near the source of timber supply rather than on the coast. It is more economical to transport sawn products than logs. Over a fairly short distance the costs of transporting by trucks and of floating are about the same, but as the distance increases, overland transport becomes proportionately much more expensive than water transport. The costs for different methods of transport are illustrated graphically in Figure 1.

FIGURE 1. - Expenses for transport of timber and saw lops with different methods of transport

Transport considerations also affect the type of sawmill that is set up. Sawmills in Sweden are of two main types; frame-saw mills with one frame saw or one or more pairs of frame saws, and circular-saw mills with a single circular saw or with one or more sets of circular breaking-down saws, rip saws and edgers. It is estimated that the timber catch region for log frame mills having one pair of log frames must be about 3-5 times larger than the area for a complete circular-saw mill. This is because a frame mill must collect a sufficiently large stock of logs to permit the required number of logs of certain dimensions to be selected. Hence log transport distances are greater for frame mills than for circular mills, and, if water transport is not available, log transport costs will be much higher. This favors the establishment of circular-saw mills rather than frame mills.

Furthermore, as the annual output of a mill grows, the transport expenses rise. Hence, in determining the most suitable size of sawmill for a particular area, transport expenses have to be taken into consideration.

Sweden is a land with a large number of lakes and waterways. For this reason, logs are very often stored in water, particularly as this facilitates sorting and prevents fungal and insect attack. Special precautions may have to be taken against freezing in winter, but it is also common for sawmills to stockpile on land enough logs to keep the sawmill in operation through the winter, in which case they are protected from decay by spraying with water.

In most Swedish frame mills the operation of sorting logs according to size is carried out in water, the various sizes being guided into different storage ponds. A large volume of logs must be collected and stored because a sufficient supply of logs of any one dimension is needed to keep the mill going for one shift. This storage increases interest costs and the risk of deterioration of the logs during storage. Land sorting arrangements exist in Sweden and work fairly well, but it is not possible to sort so many dimensions simultaneously on land as it is in water.

With circular-saw mills, logs do not need to be sorted; in fact, a mixture of logs of different dimensions is an advantage.

Frame - saw miles

The basic production line of a Swedish frame-saw mill consists of three main machines: the log-edging frame, the deal frame and the edger. These three machines are placed one behind the other (see Figure 2). The larger Swedish mills usually have several parallel production lines, of which each one, working single shifts, is capable of turning out about 5,350 standards of sawn timber a year.

The series of operations in this basic production line which consists of a single pair of frame saws is illustrated in Figure 3. The logs are barked and are then sorted according to size in the log pond. Logs of the same size are hauled up into the mill on a log chain running in a trough. As each log is required, a log kicker rolls the log down into position in front of the log-edger frame where the sawyer, controlling an infeed carriage, sets the log straight and introduces it between the feed rolls of the saw.

FIGURE 2. - Sawmill with one pair of log frames. Scale 1:300

The log is cut into a central billet, side boards and slabs. The billet is prevented by a device from going on further, while the side boards continue to the board edger. Waste slabs fall onto a waste conveyor. A lateral conveyor then brings the billet to the intake rolls of the deal frame and after adjustment the billet is introduced between the feed rolls and sawn up to the required dimensions. The interior parts give finished boards which proceed immediately to the sorting plant, while the unedged boards from the outside are separated and are conveyed to the board edger. Slabs fall onto the waste conveyor. Some examples of typical saw blade insertions used during these operations are given in Figure 4.

Modern log frames run at high speeds. Speeds between 320 and 370 strokes per minute are common, with a stroke length of 600 millimeters. An average feed speed is 25 millimeters per minute.

The board edger consists of two or more circular saws revolving on the same shaft. The distance between the saws is mechanically or hydraulically adjustable. The two-saw edger is the more common machine.

FIGURE 3.- Production survey of a gang-saw mill according to B. Thunell.

FIGURE 4. - Examples of saw blade insertions.

Larger sawmills simply consist of two or more production lines, similar to that described above, operating parallel to each other (see Figure 5). The advantage of having two or more lines working simultaneously is that logs of different sizes can be cut at the same time.

Some very small saw mills have only one log frame. Logs are edged on this frame in the morning and the billets returned on a special conveyor to the pond. In the afternoon the saw blades are changed and the billets are cut into boards on the same saw.

In all these types of mill, boards from the edger proceed to an end trimmer which generally consists of a cross conveyor feeding the boards towards a fixed trimming blade which cross-cuts one end. Before cutting, the boards are put in position by hand. Then rolls feed the boards to the other side of the conveyor where another saw trims the other end, the board lengths being fixed by a gauge on the table. The trimmed boards then proceed on the conveyor to a sorting table, often passing through an anti-blue-stain dip on the way.

In smaller mills, sorting is often done by hand by the man who does the first trimming operation. In larger mills, mechanical sorting machines are common.

Waste slabs and offcuts are either cut into firewood lengths or into chips which are used in the paper, cellulose, and wallboard industry. Sawdust is removed by special conveyors.

After the sawn and trimmed lumber is dried, it is again end-trimmed ready for stacking in shipping bundles. A modern end-trimming machine trims the lumber at both ends to the required lengths, stamps the shipping-mark at each end, registers the number of planks of each length as well as the total number and stamps a figure at one end of the plank indicating its length.

The number of men employed in a mill with one pair of log frames is usually 14: one man at the log intake, 2 sawyers, 1 assistant sawyer, 2 edger operators, 4 sorters, 1 grinder, 1 greaser, 1 waste cutter and 1 spare man. The 8-hour capacity of such a mill is 17 standards. The number of men in a mill with two pairs of log frames is 30: 2 at the intake, 2 sawyers, 2 assistant sawyers, 2 edger operators, 2 assistant edger operators, 3 trimmers, 2 waste cutters, 2 grinders, 1 greaser, 1 repair man, 8 sorters and 3 spare men. This mill has a capacity of 35 standards per 8 hours. A sawmill with three pairs of log frames employs 49 men and has a capacity of 55 standards per 8 hours. These details do not include the men employed on the log pond or in the stacking yards and kilns.

FIGURE 5. - Sawmill with 3 pairs of log frames. Scale 1:300

FIGURE 6. - Production survey of a circular-saw mill. From E. Nyholm, AB Maskifabriken, Örnsköldsvik.

FIGURE 7. - Sawmill with a circular saw and ripsaw and edger (complete circular-saw mill). Scale 1:300.

FIGURE 8. - Saw cuts in complete circular-saw mills.

FIGURE 9. - Single circular-saw mill. Scale 1:300.

FIGURE 8. - Saw cuts in complete circular-saw mills.

FIGURE 10. - Saw cuts in a single circular-saw mill.

Circular-saw mills

The complete circular-saw mill has three main machines, the breaking-down saw, the ripsaw and the edger (see Figures 6 and 7).

The blade of the breaking-down saw is mounted in a frame of wood or of welded steel. The log is laid in a table which runs on rollers, the table being driven either forwards or backwards by a feeding mechanism. After cutting a slab from the log, the thickness of the next cut is determined by pressing the sawn face against a laterally adjustable fence. The log is sawn on one, two or three sides in this machine according to its size (see Figure 8). The resulting billet is transferred to the ripsaw and the slabs either go to waste, or to the ripsaw for further treatment. At the ripsaw, which usually has power feed rollers, the billet is converted into boards. Finished boards proceed to the edger, if necessary, or, if not, directly to the stacking yard.

Waste from the three machines is conveyed under the floor to the point at which it is to be cross-cut into firewood. Waste from circular mills is rarely converted into chips. Either multiple-saw cross-cuts or single-saw swing cross-cuts are used for waste. The boards are usually trimmed with a swing crosscut saw.

Simpler circular-saw mills exist in Sweden. Some have only a breaking-down saw (Figure 9), and cuts are made as shown in Figure 10, while others have an edger as well. Some large circular-saw mills have two breaking-down saws, two ripsaws and edger. Nine men are usually required for the standard mill with three machines: 2 log rollers, 2 breaking-down sawyers, 2 ripsaw men, 1 edger operator, 1 cross-cut operator, 1 sorter. Their capacity in an 8-hour day is usually about 6.5 standards.

Consumption of raw material

In operating a sawmill the most effective use of the raw material is of the utmost importance. For the same log input volume the various sawing methods give different sawn output yields. This is due to different saw blade design, sawing precision and other factors.

The difference in yield is particularly apparent between log frame and circular sawing. The fixed positions and thinner blades of the frame saw result in greater precision and less waste than with the circular saw.


Frame mill

Complete circular

Single circular


Sawn wood




Chips for pulp












Slabs, edgings and trimmings




Shrinkage allowance




Losses owing to lack of precision in sawing will be additional, and these will probably be greater in timber sawn by circular saws than in log frames, although more modern circular sawing machines are obtaining greater precision.

Log frame sawing amounts to a mass production process in which each log is sawn with the blade positions fixed, and the sawyer merely rotates the logs to the most convenient position. In the circular saw mill, on the other hand, the sawyer can make the cut according to the peculiarities of the particular log he is handling. Results are, therefore, much more dependent on the skill of the sawyer with a circular saw than with a log frame. Canadian and Norwegian experience confirms that a skilled circular sawyer can obtain cuts with a circular saw that are just as accurate as those obtainable with a log frame. This ideal, however, is rarely achieved.

The circular-saw mill can deliver special assortments of lumber without difficulty. This would be impossible for large frame mills without a considerable rise in prices. Small circular-saw mills are most useful in supplying the home market with these mixed parcels of sawn wood. Sawn wood produced by circular saws generally fetches lower prices than the output of frame saws but the difference is very slight in times of great demand.

Log and sawn wood dimensions

Throughout most of Sweden, logs have an average length of 15 feet (4.5 m.) with a diameter at the top of 8 inches (20 cm.), and these are the measurements assumed in the calculations given so far. In some regions, however, particularly in the southern parts of Sweden, these dimensions are not representative. Many sawmills in the highlands - of Småland are obliged to cut logs 12 to 13 feet (3.7 to 4 m.) long with an average top diameter of 6 to 7 inches (15 to 18 cm.).

Although conditions vary from one sawmill to another, as a general rule the output of sawn wood will fall and expenses will rise considerably when the log size is reduced (see Figures 11 and 12). The length of the logs has a greater influence when sawing with a circular than with a frame saw. This is due to the fact that the feeding in and return of the logs consumes a greater proportion of the working time in circular sawing than

FIGURE 11. - Example of the alteration in the total cost when sawing different dimensions for the sawing method concerned, per standard, 8" log = 100 percent, log length 15'. it does in frame sawing. In a log frame it is almost possible to saw with the logs end to end, so that very little time (not more than about 5 percent) is wasted.

FIGURE 12. - Example of the alteration in total cost when sawing different log length for the sawing method concerned. Log length 15' = 100 percent, 8" log.

Waste utilization

The cost of the various methods of sawing depends very largely an the use made of waste in the sawmill. This is no longer a problem in the large sawmills in the northern part of Sweden where, with the exception of off-cuts, all the waste is utilized. The sawdust is used as fuel and the edgings and slabs are cut into chips for the manufacture of pulp or wallboard.

To allow slabs and edgings to be used in this way, the logs must be barked. Barking machines are expensive to install and are, therefore, suitable only for large sawmills. When such machines are used, presses are usually installed to reduce the moisture content of the bark to about 55 percent so that it may be used as fuel. It has been found that, provided sawing is continuous over the greater part of the year and the capacity between 2,000 and 2,500 standards, a mill with one pair of frames is the smallest in which it is economically practicable to install debarking equipment.

The installation of a chipper, on the other hand, is economically justified in a sawmill with an output of only 500 standards, provided the barking problem can be solved.

A step towards the solution of this problem is found in the semi-portable machines which operate at the stockpiles, no use being made of the bark. Tests are now being carried out to find some method of debarking slabs and edgings profitably which, if successful, may open up new developments.

Pulp mills buy up edgings and slabs in bulk and often arrange for transport as well. There is little demand in Sweden for slabs and waste as domestic fuel and the local market for wood charcoal has so declined in recent years that most sawmills have given up making charcoal from wood waste.

Cost comparisons between different types of mill

In the following comparison of the production costs of the various types of sawmill found in Sweden, all the mills are, for example, assumed to be of modern design. Their output capacity is based on 280 working days per year, although annual working time varies from 150 to 287 days. The average measurements of sawlogs are as already mentioned. The wood is assumed air-dried in open timber yards. In the timber yards of complete circular-saw mills and mills having one or two frame saws, truck transport is assumed to be by truck; also bridge-cranes are assumed to be available in mills having four or six frame saws.

Costs are based on the 1947-1948 levels (today's costs are about 50 percent higher) and are adjusted for known deviations. Average earnings are taken to be 2.30 Swedish crowns (U.S. $0.44) per hour, vacation allowance included.

In estimating depreciation, 3 percent interest on the capital and 1.5 percent interest for insurance, etc., have been added to the depreciation percentage. The time of depreciation has been estimated to be 5 years for a single circular-saw mill, 8 years for complete circular-saw mills, and 15 years for frame-saw mills. Erection costs for timber yards in complete circular-saw mills are estimated to vary in relation to yearly output. The cost of private dwellings, housing estates for workers, etc., have not been included. The costs of electric power per standard are low in Sweden, but frame mills require more power than circular-saw mills owing to their greater mechanization.

Figure 13 shows how output varies in different types of mills and Figure 14 shows the working hours per standard for these mills. Figure 15 illustrates how the running costs per standard of sawn output vary with the yearly sawn output in different types of mill.

A comparison of production costs, taking into account the use of waste, is made in Figure 16. The distance between the curves and a particular waste line is a measure of the net costs. The minimum sawing cost for varying annual outputs in different types of mill is illustrated by Figure 17.

FIGURE 13. - Output in standards per hour for different types of sawmills.

FIGURE 14. - Working hours per standard for different types of sawmills.

FIGURE 15. - Comparison of output costs at sawmills of different types. (Expenses for labor of saw and in timber yard as well a, for end-trimming and depreciations, including expenses for raw material and administration and certain general expenses.)

FIGURE 16. - Comparison of production costs exclusive of material in sawmills of different types with regard to external and internal factors and the value of the waste.

FIGURE 17. - Total cost.

FIGURE 18. - Minimum sawing costs (production costs excl. raw material) for varying annual outputs.

To assess the total cost for transport of timber and sawing, the values from Figure 17 are added to the cost of the timber transport. The cost, as calculated in this way, is shown in Figure 18.

The figures reveal that there is remarkably little difference in expenses between the different sizes of mills; the advantages of mass transport by floating are, however, apparent.

An essential condition for the erection of a large sawmill where floating transport is not possible is that there should be an adequate highway system. This is not often the case in many extensively forested areas.

For various output volumes, the type of mill which would operate with the lowest production costs in Sweden is shown below:


Output (in standards)

Type of mill

0- 50

single circular

50 - 200

circular with edger

200- 975

complete circular

975 and above

log frame

1. - Timber comes foaling down a Swedish river on its way toward the sea.

2. - Logs stopped for sorting in Swedish coastal waters: each log carries the owner's mark.

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