How to join timber together: temporary + permanent methods

Design & Technology students must be familiar with a range of temporary and permanent joining methods for timber or manufactured boards. This article helps students revise this information and concludes with sample examination questions from the Cambridge AS/A Level syllabus.

student joining timber using nails

Advantages of joining timber using temporary joining methods

  • Can be disassembled easily storage and transportation (great for flat-pack furniture)
  • Creates flexible joints that allows wood to shrink / expand with temperature changes and can accommodate some movement without breaking
  • Can often be put together with basic tools (or slotted together without any tools at all) – easier for consumers
  • Can be better for environment as fewer components / materials needed and easier to take apart to replace / repair components (less waste)

TEMPORARY JOINING METHODS FOR TIMBER

Slot together

Description

Uses

Pieces may slot together and be held in position by gravity, or using friction (jammed or wedged together)
Steel pins or wooden dowel could be used to create mechanical locking mechanisms
Can wobble / fall apart more easily / less durable
Cricket wickets jammed into hole in base
Slot-together furniture

Nails

Description

Uses

Simplest and most common joining method
Typically go through thinner piece of wood into thicker piece (nailed in at opposing angles to make more secure)
Can be removed with a claw hammer or similar tool
If temporary join, don’t punch nail heads below the surface!
Not as easily removable as other methods (can cause damage to surface of timber)
Simple butt joints
Suitable outdoors if nails are galvanised

Screws

Description

Uses

Often requires a hole with sufficient clearance for the screw to pass smoothly through in the top piece, and a thinner pilot hole in bottom piece (if wood is dense/hard)
May be countersunk
Easily removed with screwdriver
Fixing thin panels to structure beneath
Wide range of butt joints
Suitable outdoors if galvanised or stainless steel

Nuts and bolts

Description

Uses

Requires a hole with sufficient clearance for bolt shaft
Washers either side help to spread the load
Nut tightened using a socket wrench, spanner or adjustable crescent
May be counterbored
Typically used where extra strong junctions are required
Outdoor used requires galvanised or stainless steel fittings
Head of bolt is often very visible so typically used in more industrial applications rather than high-end furniture

Knock-down fittings

Description

Uses

Flat-pack furniture made from MDF or particle board often use butt joints with a range of mechanical fittings that help the produce be quickly assembled and taken down
Can be screwed, bolted, and/or use slot-in dowels
Polyethylene connecting blocks used in corner junctions
Stainless steel shelf-supports for adjustable shelving
Cover caps to conceal screw heads

Clearance: the intentional space or gap between two connecting parts or components. In fastening applications, it’s the difference between the hole diameter and the bolt/screw diameter, allowing the fastener to pass through freely without binding.

Countersunk hole: a conical or angled recess machined into the surface to fit the head of a countersunk screw.

Counterbored hole: a cylindrical recess machined into the surface around the hole opening. This accommodates hex bolt heads, washers, or other hardware, allowing them to sit below the surface level. Unlike countersunk holes, the recess has straight vertical sides.

Pilot hole: a thin initial hole used a guide. This could be used to drive a screw in straight (and more easily), or to help ensure a large hole is drilled in the right spot.

Advantages of permanent timber joining methods

  • More strong and rigid
  • Typically more durable
  • Can be higher quality items (produced by the manufacturer / maker)
types of wooden joints
Image credit © The Spruce Crafts

PERMANENT JOINING METHODS

Glued joints

Properties

Uses

Many types of wooden joints (see above)
Glued using PVA (not waterproof), waterproof wood glue, or epoxy resin (learn more about adhesives here)
May also be nailed or screwed
Complex joints such as the dovetail were traditionally made using a mixture of sawing and chiseling. Now a router with a dovetail jig can be used, or a CNC router.
Wide range of permanent structures

When joining timber, bracing and other methods of strengthening structures should be considered.

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