Chinese JoineryChinese Joinery
中文
Corners of square stock and slats
揣揣榫
chuāichuāi sǔn

Chuaichuai Sun (揣揣榫): the Tucked-Sleeve Corner Joint of Ming Furniture

Chuaichuai joint · 揣揣榫

By · Updated

Aprons, spandrels and the open frames set into cabinets are made of thin strips that have to turn corners neatly.

The best way to join them was the chuaichuai joint: each strip gives the other a tenon.

Chinese
揣揣榫 · chuāichuāi sǔn
Joins
Two thin strips at a corner
Found in
Apron-and-spandrel corners, three- and four-sided open frames
Signature parts
45° mitre · one tenon from each strip
Compare
Mitred shoulder
Drag to rotate. Slide to take the joint apart, or press Assemble to watch it go together.

How it works

Two tenons, one in each direction

Where two strips meet at a corner, each is cut with a 45° mitre and each carries one tenon that goes into the other strip. Wang Shixiang compares it to two hands each tucked into the opposite sleeve, which is where the name comes from.

Two versions

In the finest version the strips are mitred on both the front and the back, so neither tenon shows. A common Ming version is mitred only on the front: the horizontal strip is mortised for the upright’s tenon, while the upright simply meets the other strip’s tenon palm to palm.

Where it goes

It is used where an apron meets its spandrel, and in the three-sided and four-sided open frames (券口 and 圈口) fitted between legs and posts. Some spandrels on cheaper “false” trestle-leg tables are joined to the apron this way too.

Proportions in the model are illustrative.

How it's made

  1. Corner
    Step 1

    Corner

    Two strips meet at a corner.

  2. Mitre
    Step 2

    Mitre

    Both are mitred at 45°, front and back.

  3. First tenon
    Step 3

    First tenon

    The upright puts out one tenon.

  4. Second tenon
    Step 4

    Second tenon

    The rail puts out the other.

  5. Together
    Step 5

    Together

    Each tenon goes into the other strip.

  6. Sleeves
    Step 6

    Sleeves

    Like hands tucked into sleeves.

Variations

Front mitre only

Mitred on the front but not the back; only one strip is mortised.

Clamped and palm-to-palm

Single-tenon and “palm-to-palm” corners are weaker relatives.

Can you CNC this?

Hard on a 3-axis machine as drawn

Hard as drawn: both tenons leave the mitre face at 45° and are hidden on both faces, so the mortises are blind pockets in a sloping face. A version mitred only on the front, or with loose tenons, may be practical with the strips clamped at an angle.

Free STL downloads (one file per part)

Before cutting or printing, read the CNC and 3D-printing notes on tool radius, scaling the STL files and their licence.

Questions

Why “chuaichuai”?

揣 means to tuck into the sleeve: each strip tucks a tenon into the other.

Can you see the tenons?

Not in the best version: both faces are mitred and the tenons stay inside.

Where is it used?

Apron-and-spandrel corners and open frames on tables, cabinets and chairs.

Further reading
  1. 王世襄《明式家具研究》（Wang Shixiang, Research on Ming Furniture），第 106 页
  2. 王世襄《明式家具研究》（Wang Shixiang, Research on Ming Furniture），第 108 页，图 3.18a、3.18b
  3. 王世襄《明式家具研究》（Wang Shixiang, Research on Ming Furniture），第 113 页，图 3.34c