Conversion of timber

Conversion of timber
As soon as possible after felling the tree should be converted into usable timber.

There are two main methods of converting timber:

* Through and through (or Plain or Crown sawn) which produces tangential boards and
* Quarter Sawn which produces radial boards.

The Quarter sawn is far more expensive because of the need to double (or more) handle the log. There is also more wastage. It is however more decorative and less prone to cup or distort. Note also there are two ways of sawing the quarter.

Through and through produces mostly tangentially sawn timber and some quarter sawn stuff. (see diagram) Tangential timber is the most economical to produce because of the relatively less repetitive production methods. It is used extensively in the building industry.

There are other ways but they are all variations of tangential and radial cuts to obtain the best or most economical boards for the use it is to be put. These basic cuts are not always able or need to be, on the exact tangent or radius of the trunk. The cuts that fall between crown and quarter are called ‘rift’ and between ‘rift’ and ‘quarter’ are identified as ‘figured’ – see below for explanation. Boxing the heart refers to eliminating the heartwood from the boards that would otherwise produce shakes, juvenile wood or may even be rotten.

Tangential boards (crown, plain or flat sawn) are used extensively for beams and joists. They are stronger when placed correctly edge up with the load in the tangential axis. These type of boards suffer from ‘cupping’ if not carefully converted, seasoned, and stored properly. Annual growth rings form an angle less than 45 degrees.

Radial boards (radial, figured or quarter sawn) are typically cut on ‘the quarter’ and produce a pattern of the medullary rays especially in quartered oak. Such timber is expensive due to the multiple cuts required to convert this board. The radial face of the board is slightly stronger and stiffer than the tangentially face but the cross section and condition of the timber has more effect on strength. Annual growth rings form an angle greater than 45 degrees.

Crown sawn is obtained by sawing tangentially to the annual rings. It is also referred to as ‘Plain Sawn’ or ‘through and through’.

Rift sawn is the cut, which falls between crown and true quarter sawn. It is straight grained and in oak, does not reveal any ‘silver ribbon’ grain features. Quality floorboards are prepared from rift sawn timber because it wears well and shrinks less. Annual growth rings form an angle between 30 and 60 degrees.

Quarter sawn boards are radial cut from the centre of the tree. It produces the distinctive silver ribbon effect (in oak) across the whole board. Annual growth rings form an angle greater than 45 degrees. True quartered boards producing the best features will have the angle on or very much closer to 90 degrees.

‘Figured’ – is the cut between ‘rift’ and ‘true quartered’. It has varying degrees of ‘silver ribbon’ (in oak) showing through but not the full figured effect found in true quarter sawn boards.

Different species have their best features enhanced by choosing the best cut appropriate to their species.