Level 1 Diploma in Carpentry and Joinery

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Timber Conversion

1.1

Unit 115: Produce woodworking joints

Level 1 Diploma in Carpentry and Joinery

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Objectives

To be able to:

1.1 State methods of timber conversion

Level 1 Diploma in Carpentry and Joinery

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Felling Trees Transporting Logs Conversion to Timber

Origin (where timber comes from)

Level 1 Diploma in Carpentry and Joinery

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Timber Conversion: from LOG to BOARD

The way in which the raw log is converted will depend on:

• The machinery available

• The size of the log

• The condition of the log

• The wood species: the type of tree it comes from

• Economy: time and effort vs £ to be gained from conversion

• End use of the timber: Is it for structural use? Decorative use? How stable does it need to be?

Level 1 Diploma in Carpentry and Joinery

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This line is a tangent. In reference to the centre

of the circle, it is in the tangential plane.

This line is the radius. In reference to the centre of the circle, it is in the radial plane.

Geometry reminder

Level 1 Diploma in Carpentry and Joinery

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Possible timber cutsNo matter how you try to cut a log, the resulting timber section can only be:

EITHER

Tangential sawn

OR

Radial sawn

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Timber stabilityTangential sawn timber WILL cup. Shrinkage occurs along the rings. This pulls the board into a curved profile.

Radial cut timber will stay more stable. There will still be shrinkage along the rings. But because each ring is the same length, shrinkage will be even. Radial sawn: limited distortion

Tangential sawn: most shrinkage

Level 1 Diploma in Carpentry and Joinery

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Through and Through sawn Tangential sawn

Quartered (radial) conversion methods:

Quartering Classic quartersawn Traditional rift sawn (variety of methods)

Conversion Methods

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• This is the cheapest and quickest way to convert large diameter logs.

From this method will come:

• Lots of wide boards

• Little waste

• Some radial boards but mostly tangential boards (which are prone to cupping)

• Most of the small number of radial boards will have the poor quality pith (heart) in their middle

Through and Through sawn

Level 1 Diploma in Carpentry and Joinery

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Timber produced by this method will all be tangential sawn.

This method of conversion is also used to cut large diameter logs.

It is more expensive than through-through because the log is turned for each cut.

Timber produced by this method has great structural strength when laid on edge making it ideal for use as floor joists and beams.

BUT: boards produced by this method of sawing will shrink and cup a great deal.

Tangential sawn

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These are all expensive methods of conversion because of the amount of timber wasted and the greater effort required in first quartering and then repeatedly to-fro turning the log for each cut.

• Produces narrow boards.

• Produces large numbers of radial sawn boards:

Radial sawn boards are more stable in service because they distort less (holdinf their shape). This makes quartersawn boards much sought after for good class joinery work and quality decking.

Quartersawn conversion methods

Level 1 Diploma in Carpentry and Joinery

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The heart (or pith) of a log is normally prone to shakes.

It may often even be rotten (especially in oak). 

Boxing the heart refers to cutting the log to avoid the heartwood (which is sent for pulping to make paper or sheet materials like MDF).

Boxed Heart conversion