Handle Carpentry Materials

Transcription

1 Worksheet 2 Identification Handle Carpentry Materials Basic Building and Construction 1. Located in the sub-alpine heights of Mt Read near Rosebery in northwestern Tasmania, it's miraculous that 100 years of mining has not wrought the sort of havoc that copper smelting has visited on nearby Queenstown, where woodcutting and acid rain have stripped the slopes of vegetation. Second, it's good fortune that when wildfire did strike the Mt Read heights in the early '60s, killing ancient stands of King Billy pines, the flames stopped metres short of the heart of the Huon Pine that has stunned scientists around the world. Discovered in 1995 by forestry worker Mike Peterson, the ancient Huon Pine has marched its way over more than a hectare, down a hill towards the Lake Johnston glacial lake, reproducing genetically identical male copies - clones - of itself. While the oldest individual tree or stem on the site now may be 1000 to 2000 years old, the organism itself has been living there continuously for 10,500 years. 2. Plantation grown timber To help reduce the environmental impact of cutting trees for timber, special plantations of fast-growing trees are planted, specifically so they can be cut later. When the trees are used, new ones are planted, making plantation timber cheap to produce, it doesn't destroy the environment and it grows quickly. 3. Hardwood, softwood (p 232) 4. Common uses for Australian timbers Worksheet 3 Conversion 1. Definintion: 2. as above 3.

2 4. Timber shrinkage b248- f533d73d5428/13_05/toolbox13_05/unit9_selecting_timber/section4_seasoning/lesson4 _shrinkage_and_movement.htm Worksheet 4 1. Seasoning timber 2. Equilibrium moisture content of timber The moisture content of wood is directly related to the humidity and temperature of the surrounding air. The equilibrium moisture content (EMC) occurs when the wood has reached a water content equilibrium with its environment and is no longer gaining or losing moisture. In our area the EMC is about 12% 3, 4, 5, 6. Methods of seasoning timber Worksheet 5 Timber Grading Timber grading systems have been developed to ensure quality control in the industry and help consumers buy the right timber for their needs. The only problem with the grading systems is that the only ones who really understand them are those who work in the industry. What's the difference between an S1 and an F14 length of construction softwood or hardwood? Is Standard grade timber flooring inferior to Select grade? We use timber for a variety of purposes. The timber we use for building a house doesn't have to look pretty, but it does have to be strong. The timber we use for flooring or furniture making must be strong enough to bear a load and aesthetically pleasing as well. Timber grading tests and standards take both strength and appearance into consideration. Structural Timber Grading Structural timber undergoes two different types of stress tests to determine its strength and rigidity: Visual grading In a visual grading process, a trained grader examines each and every piece of timber produced. This visual inspection is undertaken in accordance with either the hardwood or softwood visual grading standards, which define rules as to the types, sizes and positions of physical characteristics that are allowed into each 'group' or structural grade of material. Q 1. The size and position of knots and other potential strength reducing characteristics in each piece is compared with the size and position of these

3 characteristics allowed in the various grading classifications. The highest grades allow fewer and smaller characteristics in each piece of timber. Unseasoned timbers are graded S1 through S7 and seasoned timbers are graded SD1 through SD8. In both cases, the lower the number, the higher the strength of the timber. Clear grade is the highest grade of board and free of all imperfections and is extensively used for the production of mouldings and products requiring the ultimate fine, knot free appearance. Products manufactured from this grade are suited for clear finishing when used internally, or staining or painting when used externally Select Grade is a subtle feature grade of timber which provides a limited variation in natural characteristics. The features that are present are relatively small and few in number. Mechanical stress testing is performed to determine the rigidity or strength of timber. Mechanical timber grading is highly technical, but for practical purposes, the main thing you need to know is that in this case, the higher the number, the stronger the timber. The mechanical grading system grades timbers regardless of species from F1 (very weak) to F34 (extremely dense). For example, radiata pine is often graded between F5 and F14, while tallowwood, an extremely dense hardwood, is usually graded between F17 and F34 Q 4. An F grade is a measure of the bending strength of a piece of timber. 'F' stands for force in megapascals (MPa), and is the amount of force a piece of timber can withstand without bending beyond an acceptable limit. A piece graded to F11, for example, will have a safe working stress in bending of 11 MPa. Q 5 COLOUR MARKING is sometimes used on the timber to indicate the stress ("F") grade. The colours and grades are:- Stress Grade F4 F5 F7 F8 F11 F14 F17 F22 F27 F34 Red Black Blue Green Purple Orange Yellow Pink Turquoise Colour

4 Using MGP ( merchantable grade timber) in place of F graded timber It's important to note that although MGP material may be substituted for F graded material, as shown below, F graded material must not be used where MGP material has been specified. This is because the MGP grades have design tables for a range of properties, whereas F grades are based on bending strength only. So it is possible that the architect or builder who has specified an MGP grade for a structural member is relying on design characteristics such as compressive strength or shear strength, which would not be accounted for in an F graded piece. Below are the three main MGP grades and the F grades they can replace. MGP 10 can replace F5 MGP 12 can replace F8 MGP 15 can replace F11 Work sheet 6 MEASUREMENT of TIMBER and TERMINOLOGY 3. Scantling is timber with width up to 150mm and mm thick used for house construction. Standard width and thickness for scantling used for internal studs is 70x35, however 90x45 is preferred for weight bearing walls. 4. Timber manufacture Sizes of Sawn or Milled Timber and Wood Products Sawn timber Sizes for sawn timber (with a sawn or a smooth surface) are usually a nominal size with a positive and a negative tolerance. The tolerances are tighter for timber specified as sized or gauged timber or as dressed timber. However the sizes for dressed timber (and to a lesser extent for sized or gauged timber) are smaller than the sizes for sawn timber of the same nominal size. A piece of sawn timber will lose some of its dimension as part as the dressing process leaving the dressed piece with a finished size less than the nominal size. For example, when a piece of sawn timber with a nominal size of 100 x 100 mm is dressed all round (DAR) it will have a finished size of say 93 x 93 mm. The dressed piece of timber has historically been described as either 100 x 100 mm dressed or dressed to 93 x 93 mm finished size. It is far better to specify dressed timber by its finished size. i. Sawn timber Sawn timber is timber that comes straight from the saw. Sawn timber is generally cut into varying rectangular widths, thicknesses and lengths Nominal sizes for sawn timber include 25mm, 50mm, 100mm, 150mm ii. Dressed Timber Timber that has been processed through a planing machine in order to attain a smooth surface.

5 Finished sizes of dressed timber include 19mm, 42mm, 92mm, 140mm. Industry Standard Timber Sizes 5. Milled Timber ms-historical.pdf