Materials Technology wood

1. Materials Technology wood Week 8 – lesson 2

2. Homework

3. Felling Felling is the harvesting or cutting down of timber. Trees are usually cut down in the autumn and winter. Although they can be cut down in summer there are two main advantages to winter felling What are they?

4. Conversion of timber After the tree is felled, the branches stripped off and the logs cut to size the logs are transported to the sawmill. What happens at the sawmill?

5. Why are logs converted into boards?

6. Methods of conversion: The way in which logs are cut will affect the appearance and strength of the board. The three main methods are.... Through and through sawing Quarter sawing Tangential sawing.

7. Through and through sawing Very popular form of conversion. The logs are cut in parallel cuts in the direction of the grain. Sketch this

9. Advantages: • Cheapest form of conversion. • Very little waste, maximum amount of timber is obtained. • Machining is straightforward reducing labour costs Disadvantages: • The timber shows no particular grain pattern • This method of sawing is not suitable for structural timber • With this method cupping of the timber is a problem

10. Quarter sawing Sketch this

11. Advantages: An attractive grain pattern is obtained These boards are more stable and shrink less The timber wears more evenly. This is important in flooring, for example. Disadvantages: There is a lot more work needed in the machining of the log as it has to be turned for each cut More expensive.

12. Tangential sawing: Sketch this The cut is taken tangential to the annual rings.