ESD Term 3 Revision (exam ver)

5 main forces a structure should be able to resist

shear, bending, compression, torsion, tension

Why should rigid structures need a measure of flexibility?

1. Allows for absorption of stress

2. Completely rigid structures are more likely to break under pressure

Face-side

Face-edge

What is kerf?

The width of a cut made by a saw

Purpose of a countersink

Made from HSS, it widens a previously drilled hole, so a countersunk screw head can be screwed level with the wood

Finger joint

What is ‘setting time’?

1. Most adhesives are made of solid glue particles dissolved in a solvent (water/spirit)

2. Solvent needs to dry before adhesive works

3. Setting time is the time it takes for drying

How can you use glue to fill a poorly cut joint?

1. Saw some waste wood of the same type and mix the sawdust with glue, into a paste

2. Fill the gap with the glue, with some excess

3. Sand off excess

What are the two parts of a wood laminate?

1. Veneers

2. PVA glue

Laminating a curved strip

Why is laminated wood tougher than a solid section of wood?

A crack would stop at the glue line and won’t go through it all

What is fusibility? Give an example.

• measure of how easy it is to melt the material

• highly fusible material has a low melting point

• e.g. tungsten

Difference between elastic and plastic?

Elastic: temporary & will return to original state
Plastic: permanent & will stay in new state

Strength measurements

• Tensile – resists being stretched

• Shear – resists sliding forces

• Compressive – resists being crushed

• Torsional – resists twisting

• Bending – resists bending

Red colour sign means:

things you can’t do

Yellow colour sign means:

warning signs

Blue colour sign means:

things that must be done

head protection must be worn

eye protection must be worn

ear protection must be worn

no naked flames

Name A.

countersink

Name B.

clearance hole

Name C.

pilot hole

PVA setting time

1 hr

Synthetic resin setting time

2-6 hrs

Contact adhesive setting time

instant

Glue stick setting time

15s

Forces acting on a beam & how they affect the surface

Cross sections