- Decides
- How strong and rigid the product is, how square it stands and how it ships.
- Goes wrong as
- Loose chairs, racked cabinets, open joints, stripped fittings and glue marks under the finish.
- Used for
- Furniture components, Cabinet doors and fronts, Millwork and mouldings, CNC routed parts, Wood packaging and boxes, Pallets and crates
Processes / Step 9 of 11
Joinery and Assembly: How Wood Parts Become Furniture
Machined parts are joined with glued joints, mechanical fittings or both, in jigs that hold them square. The joint choice decides strength, cost and whether the product ships assembled or flat.
Joinery is where separate parts become a chair, a table or a cabinet. The joint chosen at the design stage sets the machining, the assembly time, the strength and the shipping method. A glued mortise and tenon chair frame is rigid for decades but ships at full size. A cabinet held together by cam locks and dowels packs flat and goes together at the store or the customer's home, but only if every hole is in the right place.
In a factory, joints are cut on tenoners, mortisers, multi-spindle boring machines and CNC routers, then assembled in jigs and case clamps that pull the parts tight and square. Glue is spread, parts are pressed, diagonals are checked and squeeze-out is cleaned before it hardens. Each of these steps can be done carefully or quickly, and the difference shows as a chair that rocks on a flat floor or a cabinet whose doors do not line up.
For a buyer, the key decisions are the joint type for each connection, the hardware, the glue, the squareness tolerance and whether the product ships assembled, partly assembled or knocked down. Those choices also set the container count, which can matter as much as the unit price.
Where it sits in the chain
- 01Drying
- 02Rough milling
- 03Jointing & gluing
- 04Planing
- 05CNC routing
- 06Turning
- 07Bending
- 08Veneering
- 09Assembly
- 10Finishing
- 11QC and packing
Not every product goes through every step. A pallet skips finishing, a turned leg skips veneering.
Methods and machines
What a factory may run for joinery and assembly, and where each method fits. Ask which one your parts will go through.
| Method | What it does | Fits |
|---|---|---|
| Mortise and tenon | A tongue on one part fits a cut pocket in the other and is glued. Machine tenoners and mortisers cut both to matching size. | Chair and table frames, doors and any joint that carries racking load. |
| Dowel joints | Fluted hardwood dowels are glued into matching holes bored on multi-spindle machines. Cabinet makers often use a 32 mm hole system. | Case furniture, frames and panels where many identical joints are needed quickly. |
| Loose (floating) tenons | A separate flat tenon is glued into two matching slots cut with a router or a special joiner. | Frames and table aprons where a solid tenon would waste length or the parts meet at an angle. |
| Biscuits and pocket screws | Biscuits are thin compressed wood ovals glued into slots, mainly for alignment. Pocket screws are driven at an angle through a hidden hole. | Panel alignment, face frames and light frames. Not for chair joints that carry racking load. |
| Knock-down fittings | Cam locks, cross dowels with bolts, bed bolts, threaded inserts and connector screws let the product be taken apart and shipped flat. | Flat-pack cabinets, beds, large tables and anything that must fit through a door. |
| Corner blocks and brackets | Glued and screwed blocks, or metal brackets with a bolt to the leg, brace the joint between apron and leg. | Table and chair frames, often combined with dowels or tenons. |
What you specify
These points decide whether two factories quote the same thing. Put them in the RFQ or the purchase order.
- Joint per connectionName the joint for each critical connection on the drawing, for example tenon at seat rail to back leg, dowels at stretchers. "Solid construction" says nothing.
- GlueState the glue type and its water resistance class, for example a PVA meeting EN 204 D3 for furniture used in kitchens and bathrooms.
- HardwareSpecify knock-down fittings by type, size and finish. State how hardware bags are packed and labeled.
- Squareness and levelSet a tolerance on diagonals for cases and frames and on rock for chairs and tables, measured on a flat surface.
- Shipping stateSay whether the product ships fully assembled, with legs off or fully knocked down. Say who writes and tests the assembly instructions.
- Strength testingName the test standard your market expects for the product type, and ask whether the factory has run it on a sample.
Typical values
Published and common industry figures. They vary by species, product and factory, so treat them as a starting point and confirm on the quote.
| Item | Typical value | Note |
|---|---|---|
| Common dowel diameters | 8 mm and 10 mm | Fluted hardwood dowels in case and frame furniture. Typical. |
| Cabinet hole system | 32 mm spacing | Industry convention for shelf pins, hinges and connectors in case furniture. |
| PVA clamp time | About 30 to 60 minutes | At room temperature for unstressed joints. Full strength takes about a day. Typical, see the glue data sheet. |
| Diagonal difference on a cabinet case | Often within 1 to 2 mm | Set by the buyer for the product size. Typical. |
| Container use, flat-pack vs assembled | Flat-pack often fits several times more units | Depends heavily on the product. Ask the factory for a loading plan of both versions. |
Defects and how to prevent them
What goes wrong at this step, why it happens and what to ask before production so it does not reach your warehouse.
| Defect | Usual cause | What to ask or check |
|---|---|---|
| Loose or open joints | Tenons or dowels cut undersize, glue starved joints or wood that was too wet and shrank after assembly. | Ask for a sample joint cut open, and moisture readings on parts before glue-up. |
| Racked or out of square cases | Parts clamped without a jig or diagonals not checked before the glue set. | Ask to see the jigs and case clamps, and specify a diagonal tolerance. |
| Chairs and tables that rock | Legs not cut on one plane, or the frame twisted in assembly. | Ask for a rock check on a flat table on every unit or on a stated sample. |
| Glue squeeze-out under the finish | Glue wiped into the grain or left to dry on show surfaces. It blocks stain and shows as pale patches. | Ask how squeeze-out is removed and inspect stained samples at joints. |
| Misaligned knock-down holes | Boring jigs or CNC programs off position, or parts from different batches mixed. | Ask for a test assembly from a sealed carton using only the parts and instructions inside. |
| Split parts at dowels or screws | Dowels too tight, pilot holes missing or screws driven near the end of a part. | Approve a first article with all fittings installed. |
Questions to ask the factory
Ask on a video call with the line running. Keep the answers in writing.
- Which joint do you use at each critical connection, and can you show a sample cut open?
- Which glue do you use, and what water resistance class does it meet?
- Do you assemble in jigs, and how do you check squareness and rock?
- Who supplies your knock-down fittings, and do you test-assemble from a packed carton?
- Have you run strength or stability tests on a similar product for my market?
- What is the container count for assembled and flat-pack versions of this product?
How to write it in the RFQ
Example lines you can adapt.
- Dining chair: mortise and tenon at seat rails and back legs, dowelled stretchers, PVA glue to EN 204 D3, rock no more than the stated limit on a flat surface.
- Sideboard: knock-down construction with cam locks and dowels on 32 mm system, diagonals within 2 mm, test assembly from a sealed carton before shipment.
Send your RFQ and we match it with up to 3 factories that run this step for your product.
Materials and joinery and assembly
How common species and panels behave at this step.
- BeechHard and strong, holds tenons and dowels well. The usual species for dowels and many chair frames.
- White oakStrong in mortise and tenon joints. Tannins can stain black around steel screws and fittings in damp conditions.
- RubberwoodMachines and glues well, common in knock-down furniture. Softer than beech, so screw holes need correct pilot sizes.
- ParticleboardJoined with dowels, cam locks and connector screws. Holds screws poorly on edges and cannot be reassembled many times.
- PlywoodHolds screws and fittings better than particleboard. Edge screws need care to avoid splitting the plies.
Questions buyers ask about joinery and assembly
Deeper guides on this step:
- Furniture Joinery Types for Production: Dowel, Mortise and Knock-Down
- How Container Loading Changes the Price of Wood Products
- Upholstered Furniture Frames: Wood Species, Joints and Specs to Request
Background reading: Woodworking joints (Wikipedia)
Is knock-down furniture weaker than assembled furniture?
Not always, but it depends more on fitting quality and hole accuracy. A well designed knock-down frame with dowels for alignment and bolts for clamping can be very rigid. Cam locks alone in particleboard loosen if the product is moved or reassembled often.
Should chairs ship assembled?
Glued chairs are strongest. Many importers ship chairs with the seat and back assembled and legs or the back frame bolted on by the customer, which cuts container volume. Ask for a strength test on the knocked down design.
What tests check furniture strength?
It depends on product and market. Seating and tables have strength and durability tests in EN and ISO standards, office furniture has BIFMA standards and clothing storage units sold in the United States have tip-over requirements under ASTM F2057. Ask which tests your buyer requires.
Do I need a dry-fit before production?
Yes. A first article assembled from production parts, and for knock-down products from a packed carton with its own instructions, catches hole errors and missing hardware before thousands of units are made.
Have a drawing ready?
Send it with species, finish and quantity. We match you with up to 3 wood manufacturers and reply within 24 business hours.
Get matched with a wood manufacturer