To make a wooden pattern with required dimensions from the given work piece by using carpentry tools.
The pattern is the principal tool during the casting process. It can be said as a model or the casting to be done. It is a model or form around which sand is packed to give rise to a cavity known as mould cavity. When this mould/cavity is filled with molten metal, molten metal solidifies and produces a casting (product). So the pattern is replica of the final product.
The most commonly used pattern material is wood, since it is readily available and of low weight. Also, it can be easily shaped and is relatively cheap.
Apparatus/ Equipment required:
- Try square
- Steel rule
- Tenon saw
- Rip saw
- Firmer chisel
- Wood Rasp file
- Emery paper
- Pattern Material used: Soft wood (Gamari wood) of size 155 x 52 x 25 mm.
- The given work piece is firmly clamped in the vice and any two adjacent surfaces are kept in plane surface to get right angles using the jack plane.
- Using the try square, the right angles of planned faces are checked.
- Now the other two surfaces are planned to get smooth surface.
- Using the steel rule and try square, marking is done.
- The unwanted portions of wood are removed by using the tenon saw and firmer chisel.
- Use wood rasp file to make uneven surface smoother.
- Then use emery paper to get more smooth external surfaces.
- Finally, the finished job is checked for required size and shape using the steel rule and try square.
- Wood should be free from moisture.
- Marking is to be done without parallax error.
- Care should be taken while chiseling.
- One should not use defective or damaged carpentry tools while carrying out work in carpentry shop.