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a) Describe, with sketches, the following log conversion methods.
i) Through and through sawn.
ii) Quarter sawn.
b) State which method is best for wide table top boards (explain your choice of method).
Through and Through
Through and Through - slab - or rift sawn. The timber log is passes through the saw where a plank is removed then the log passed through the saw again. This method of sawing is the cheapest, gets most timber out of the log and produces wide boards. but the boards tend to curl and cup when drying.
Tangental Sawn
Tangential sawn or round the log here each time a board is removed the log is rotated 90 degrees then another board is removed. These 'tangental' boards are generally stronger as the annual rings are longest on the face of the boards . Also this type of conversion creates attractive grain patterns on the face of the boards as shown here on this European Walnut sample.
Small Timber Logs
Small timber logs grown around 100 years generally have tangential 'edge boards' removed then the centre is split to get 2 or 3 (225 x 75mm) planks.
Quarter Sawn
Quarter Sawing is generally reserved for hardwood timber where stability (and in some cases madullary fugure is required as shown here on this Japanese Oak sample). Quarter sawing is expensive in production time and also in the waste produced
Timber sample picture curtesy of TRADA species database
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