1. Construction and Assembly

2. Objectives All students will:
Be able to identify the pros and cons of fixings and joints.
Know that construction methods can be both temporary and permanent.
Name at least three different types of fixings/joints.

3. Screws/Bolts/Hinges…
All these fixings can be both permanent and temporary and offer a very cost
effective and simple way to assemble a product.
For you exam you will need to have knowledge of different types, what they are used
for and their benefits.
Question:
State another advantage to screws over using a dovetail joint…
Answer:
Standardised parts and sizes, easier to source
Can buy in bulk to make it a lot cheaper, thus lowering the cost price of the design
Very fast to install

4. Screws Countersunk Screws Round Head Screw Machine Screw/Wing Nut
Used when the top of the screw needs to be flush with the timber.
Pozidriv or Slothead are available.
Round Head Screw
Used when the screws do not need to sit flush in the timber. These can look decorative when made from brass.
Machine Screw/Wing Nut
The machine screw is different due to it’s flat bottom. Often used like a bolt for joining wood. (Some tables have them, along with a corner plate.)
The wing-nut helps to tighten the fixing. The wing-nut can look unsightly.

5. Bolts
….are used to join pieces together either permanently or temporarily.
Coach Bolt
The coach bolt has a square collar under the domed head.
A washer is normally placed before the nut to stop it sinking into the wood as it is turned.
Machine Bolt
Two spanners are needed to tighten this nut and bolt.
The first spanner fits round the hexagonal head of the bolt and a second spanner is used to tighten the hexagonal nut.
Used mostly with metals.

6. Hinges
Most common types are “Butt” and “Butterfly” hinges They ideally should sit flush by recessing.
Other types include:
Flush
Concealed
Piano
Products hinges are used on include…:

7. Knock Down Fittings
Knock-Down Fittings are components that can be put together quickly and more efficiently than traditional joints
Usually a temporary joint but can be permanent
Very simple to understand how to use
Manufactured in very high volume – makes them very cost effective
Ideal for use on man made boards: chipboard, MDF etc.
Wide range of options available to suit an application
Use only basic tools such as allen keys and screw drivers
Spares are readily available
After time, fixings can become tired and worn when constantly
reassembled
Sometimes need to be reinforced with glue to make them stronger
If a fixing is lost, this can compromise the furniture

8. PLASTIC CORNER BLOCK TWO BLOCK FITTING RIGID JOINT:
The corner block is pressed against the two pieces of material (normally wood based). Screws are used to fix the block into position.
This type of joint is used to fit modern kitchen cabinets.
Strong
Can be dismantled using only a screwdriver
Good for difficult corners!
TWO BLOCK FITTING
These are made from plastic. A bolt passes through the first fitting into the thread of the second.
As the bolt is tightened it draws the two fittings together.
Strong
Can be dismantled
Quick way to hold two corner pieces together
RIGID JOINT:
These are normally injection moulded in plastic which makes them durable and rigid. Screws pass through the four holes which hold the sides at each corner firmly together.
Often used on bookcases
Can look a little unslightly!

9. BARREL NUT AND BOLT CAM LOCK FITTING CORNER PLATE
Often used in flat pack furniture, the bolt is inserted into the “barrel” which contains a thread. This locks the frame together.
Quick to dismantle
Excellent replacement for lap joints
CAM LOCK FITTING
You will have seen this one on IKEA furniture! (MALM!)
The cam has a slot that “catches” the head of the screw, and as it twists, locks into position.
Only need a screwdriver
No glue needed, very sturdy
CORNER PLATE
Often made from galvanised steel, or even aluminium, these plates are used on the underside of tables.
The two dome screws attach the legs, and the wing-nut bolt locates the table leg and tightens everything together.
Ideal for joining 3 components
Quick to assemble
Needs to be tightened occasionally

10. Wood Joints…
Joints are an excellent way of joining timber together, normally
natural timber (MDF etc doesn’t joint well) without the need for
extra parts.
Its very cost effective, cheaper than using screws or bolts.
Joints when done correctly, can look aesthetically pleasing.
Tools required:
Tenon saw
Chisel
Mallet
PVA Glue

11. Wood Joints Mortise and Tenon
A rectangular hole is chiselled in one piece of timber, and the other part has a section that fits flush.
Very strong when glued together (PVA)
Lap
Areas of wood are removed on each piece of wood so that the joint lines up.
Easy to mark out and used where joints do not need to be strong.
Tenon
Mortise

12. Wood Joints
Dovetail
Very intricate and attractive joint. Extremely strong and almost impossible to pull apart.
Used on items that make a feature of the joint.
Bridle
Used in construction of lightweight things where little strength is needed.
Sections of material are removed, similar to a mortise and tenon joint.

13. Wood Joints Dowelled Mortise and Tenon
Same as normal, but using pieces of dowel to join the wood (with PVA glue)
Used in modern furnitue, not overly strong.
Cross Halved
This joint takes even amounts of wood away to fit the 2 pieces together.
Glued together and strong.

14. Further Info… www.technologystudent.com
Doddle
ttings.pdf