Bench work & joints · National 5
Flat-frame joints
9 cards · 6 quiz · 0 exam
Practical Woodworking · National 5 · mrkellydt.co.uk
What you're learning in this topic
Learning intention WALT
We are learning about flat-frame joints, specifically to:
know
- butt, mitre, dowel, halving, bridle and haunched mortise and tenon corner joints
- T joints, cross halving and dovetail halving
understand
- the stages in marking and cutting a flat-frame joint
be able to
- choose a flat-frame joint for a situation and justify it
- cut flat-frame joints with gaps no more than 1 mm
Success criteria WILF
- I can identify butt, mitre, dowel, halving, bridle and haunched mortise and tenon corner joints
- I can identify T joints, cross halving and dovetail halving
- I can choose a flat-frame joint for a situation and justify it
- I can describe the stages in marking and cutting a flat-frame joint
- I can cut flat-frame joints with gaps no more than 1 mm
What is a flat frame?
A flat frame is made from lengths of wood joined at the corners and middle, like a door, a table frame or a chair back. The upright parts are stiles; the cross pieces are rails.
Corner joints
| Joint | Notes |
|---|---|
| Butt | Simplest; weak unless reinforced with dowels, screws or a corner block |
| Mitre | 45° on both parts; hides end grain, so it looks neat (picture frames); weak without reinforcement |
| Dowel | Butt joint strengthened with glued dowels; needs accurate drilling (use a jig) |
| Corner halving | Half the thickness removed from each part; easy to cut, good glue area |
| Corner bridle | An open slot and tongue; strong, large glue area |
| Haunched mortise and tenon | The haunch stops the rail twisting and fills the groove end in a panelled frame; very strong at a corner |
T joints and cross joints
- T halving and T bridle: a rail joining part-way along a stile.
- Stub mortise and tenon: the tenon doesn't go all the way through, so it's hidden.
- Through mortise and tenon: the tenon goes right through: very strong, and can be wedged.
- Cross halving: two parts crossing, each cut half way.
- Dovetail halving: a halving with angled sides that resists being pulled apart.
A tenon is normally one third of the thickness of the wood.
Choosing a flat-frame joint
- Strength needed: mortise and tenon or bridle for chairs and tables; halving for light frames.
- Appearance: mitre hides end grain; stub tenon is hidden; through tenon shows.
- Skill and time: halving is quickest; mortise and tenon takes longest.
- Advantages of traditional joints over knock-down fittings: no extra parts to buy, they look attractive and show craft skill, a large glue area makes them permanent, and they don't work loose.
Cutting a corner halving (stages)
- Mark the width of the joining piece across both parts with a try square and marking knife.
- Set a marking gauge to half the thickness and gauge from the face side on both parts.
- Shade the waste.
- Saw down the grain on the waste side of the gauge line with a tenon saw.
- Saw across the shoulder line to remove the waste.
- Clean up with a chisel, then test the fit.
Key terms
| Stile | Upright part of a frame |
|---|---|
| Rail | Horizontal part of a frame |
| Haunch | Short step on a tenon that stops twisting and fills the groove end |
| Stub tenon | Doesn't go all the way through, so it's hidden |
| Mitre joint | 45° on both parts; hides end grain |
| Bridle joint | Open slot and tongue: strong with a large glue area |
| Dovetail halving | Angled halving that resists pulling apart |
| Tenon thickness | About one third of the wood's thickness |
| Advantage of traditional joints over knock-down fittings | No extra parts, attractive, permanent with a large glue area |
Quick check
1. Which joint hides the end grain at a picture-frame corner?
- Butt
- Mitre
- Corner halving
- Bridle
Show answer
B: Mitre. Mitres meet at 45°, so no end grain shows.
2. What does the haunch on a haunched mortise and tenon do?
- Decorates the joint so that it looks better
- Makes the joint knock-down for flat packing
- Stops the rail twisting and fills the groove end
- Holds extra glue inside the mortise
Show answer
C: Stops the rail twisting and fills the groove end. It adds strength at a corner and fills the panel groove.
3. Which joint is quickest to cut for a light frame?
- Through mortise and tenon
- Haunched mortise and tenon
- Dovetail halving
- Halving
Show answer
D: Halving. Halvings are quick and simple.
4. Which halving joint resists being pulled apart?
- Dovetail halving
- T halving
- Cross halving
- Corner halving
Show answer
A: Dovetail halving. The angled sides lock it.
5. How thick is a tenon usually?
- Half the wood
- One third of the wood
- One quarter of the wood
- The full thickness
Show answer
B: One third of the wood. The ratio is about one third.
6. Which is an advantage of a traditional joint over a knock-down fitting?
- It can be taken apart again easily
- It is always quicker to make by hand
- It needs no extra parts to buy
- It needs no glue to hold it together
Show answer
C: It needs no extra parts to buy. Knock-down fittings are bought parts; traditional joints are cut from the wood.
Printable worksheet
An I do, we do, you do worksheet for this topic, with a separate answer sheet.