Match the number and the pattern from the coded table below with the letters from the table to reveal the class topic.Example 3<><. 4;-) equals “SO”

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1 E O R

2 C V N

3 V S I

4 O N T

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CONVERSION

Conversion of Timber

Grade 8

The Conversion of timber process

video clip of the conversion process

What is conversion of timber

• The process of cutting logs into timber is called conversion.

• There are several methods of conversion, each of which has some special advantage. For some timbers conversion must take place before the log has time to dry out and shrink.

What are some of the factors that determine the type of cut?

The way the cuts are made will depend on several factors ,some of which are:

• The type of sawing machine• The condition of the log• Economy• The size of log• The wood species• The end use of resulting timber

What are the types of sawn Lumber?

Methods of conversion of timber

There are three main methods of conversion of timber. They are :

• Plain sawn

• Quarter sawn

• Rift sawn

Plain sawn

• Plain sawn which is sometimes called through-and-through or slash sawing. In plain sawing, the saw cut forms a tangent to one of the annual rings. There are several variations of plain sawing

Picture of plain sawn

Plain Sawn

Advantages of plain sawn• The log is easily-manipulated and frequent

turning is not required. • There is no waste of timber.• It is a cheaper method

Disadvantage of plain sawn• It has the disadvantage that shrinkage may tend

to warp and split the boards.• They also tend to absorb more moisture from the

air which can also lead to unwanted movement

Quarter Sawn

• Quarter sawn lumber comes at a premium due to the labor it takes to mill each plank. To mill quarter sawn wood, each log is sawed at a radial angle into four quarters. Then each quarter is plain sawn. This method of quarter sawing does leave some waste, but much less than rift sawn lumber.

Quarter sawn

• In quarter sawing , the saw cut is made at right angles to the annual rings. This method is used particularly to produce figured oak. A quarter sawn board will therefore expose the rays where as a plain sawn one would cut across them.

Picture of Quarter sawn

Quarter sawn

Advantages of Quarter Sawn• Smoother surface due to less distinct grain• Decreased expansion and contraction on the plank’s

width• Twisting, cupping, and warping resistance• Ages evenly over time• Chances of surface checking are significantly reduced• More resistant to moisture penetration• Enhanced paint retention

Quarter sawn

Disadvantage of Quarter Sawn

• The cutting operation is much more complicated and involves more waste.

• The boards are rather narrow.

• It is an expensive method

Rift sawn

• Milling rift sawn lumber takes more time and labor. It also has unique benefits over quarter and plain sawn lumber. Furniture makers depend on this cut of wood for the vertical grain that is shown from all sides. This linear grain pattern is achieved by milled perpendicular to log's growth rings. The log is milled carefully on an angle between 45° to 75°.

Rift sawn

Rift sawn

Advantages of Rift Sawn

• Ideal for custom furniture makers to use for table, chair and other straight pieces

• The most dimensionally stable cut of lumber available

• Unique, linear appearance on both sides of the lumber planks

• Rift sawn lumber is dimensionally superior to both plain sawn and quarter sawn lumber.

Rift Sawn

Disadvantage of Rift Sawn

• they also produce the most waste.

• rift sawn lumber will cost more per board foot than either quarter sawn and plain sawn lumber.

Plain and Quarter

Sawn lumber

                                                   

 

                                                    

 

                                                   

Plain Sawn vs Quarter Sawn vs Rift Sawn

•Faster to produce•More affordable•Displays varied grain patterns & the unique "cathedral" appearance•Readily available

 •More stable than plain sawn lumber•Increased moisture resistance•Less likely to cup, twist & warp•Beautiful ribbon aka "fleck" patterns are prevalent in species like White Oak & Red Oak•Less expensive than rift sawn lumber

 •Ideal for custom furniture makers to use for table, chair and other straight pieces•The most dimensionally stable cut of lumber available•Unique, linear appearance on both sides of the lumber planks

Plain sawn Vs Quarter sawn

Why is it important to have allowance cut the

logs into timber?

• When sawing, an allowance is made for shrinkage and for planing the boards to the required finished sizes.

summary

classwork

• Write a letter to their best friend telling him or her how logs are converted into timber .