Assembling chairs on site: hardware, torque and time

Containers of 400 KD chairs are four pallets of neatly flat-packed promise. They become dining rooms only if somebody with the right driver bit and the right torque setting works through them in the right order.

Published by JPChairs · Chair manufacturer in Foshan, China · 2026-10-19

KD or welded: the trade you are making

Knock-down frames are neither the cheap nor the dear option. They are a different balance of freight, labour and risk, and the decision belongs on unit price plus those three, not price alone.

• Freight: a dining frame that stacks six high to 1.10 m as a welded unit fills a 40HC at roughly 480 to 520 pieces. Knocked down, with seats boxed separately, it takes 560 to 600, about 15 to 18 per cent more pieces for the same ocean freight.
• Labour: budget 9 to 15 minutes per chair for one trained person with a cordless driver, so 400 chairs is 60 to 100 working hours.
• Consistency: a welded frame leaves the factory square. A KD frame depends on whoever holds the driver, so the work has to be specified rather than assumed.
• Repair: a KD joint unbolts and takes a replacement leg in about 12 minutes. A welded frame with a bent leg usually needs the whole frame, and the freight costs more than the part.

For venues that reset the room daily we usually recommend welded. For air freight, tight stairwells or anything carried up two flights, KD wins every time.

Fastener sizes that survive service

Most loose chairs in the field are not broken, they are under-torqued. The specification that prevents it is short.

• M6 into a steel threaded insert: engagement of at least 9 mm, which is 1.5 times the diameter, giving a pull-out of 1.9 to 2.4 kN in 18 mm plywood.
• M8 into a steel nut or insert: 18 to 22 Nm, used on the seat-to-frame joint of stackable banquet frames.
• Directly into solid beech or oak: use a 5 by 50 mm or 6 by 60 mm confirmat screw, not a wood screw. Pull-out rises to 1.4 to 1.8 kN against 0.8 to 1.1 kN for a 4.5 by 40 mm screw in the same timber.
• Always under the head: a flat washer plus a split lock washer, or a nyloc nut. Omitting the washer alone costs 20 to 30 per cent of clamp load because friction eats the torque.
• Metal to metal: medium-strength threadlocker on any bolt that will be cycled, applied to the last 4 mm of thread.

Torque numbers, and where most people get them wrong

Three settings cover almost every chair we ship, and the fourth line in this list is the one that causes returns.

• M6 into a steel insert: 8 to 10 Nm.
• M6 or confirmat into hardwood: 4 to 6 Nm. Above roughly 8 Nm the thread strips in oak and the pull-out figure halves.
• M8 into steel: 18 to 22 Nm.
• Clutch drift: a cordless driver drifts 10 to 15 per cent after about 20,000 cycles. Calibrate every 6 months or every three projects, whichever comes first.
• The wrong tool: an impact driver at full power reaches 60 to 180 Nm and destroys the joint before it looks wrong. Use the clutch, or finish the last quarter turn with a manual torque driver.

We print those three figures on the instruction sheet in every carton, and for projects above 300 chairs we can ship a pre-set torque driver in a hard case.

Sequence: fit loose, torque last

The order matters more than the force. Four steps, and they cut the rocking complaints to almost nothing.

• Stage first. Unpack every carton and lay the parts on the flattened cartons or on blankets, so both the floor and the finish survive.
• Fit every bolt finger-tight on all four legs or both sides before torquing any of them. Tightening one corner fully leaves 1.5 to 3 mm of twist, and the chair then rocks on tile.
• Torque in a cross pattern, the same order every time, in two passes: 60 per cent of the final figure first, then the full figure.
• Wobble check on a level hard floor, never on carpet. Three-point contact is normal on tile, but lift above 2 mm is a reject.

Finish with a clean. Silicone-free cleaner and two cloths, because assembly dust left on a powder-coated frame scratches it inside the first week of service.

How many hours to fit out a room

These are working figures from recent fit-outs with two people and no lift access.

• Unboxing, removing protective wrap and staging: 1.5 to 2 minutes per chair.
• Assembly with a pre-set clutch driver: 3 to 5 minutes per chair, falling to 2.5 minutes once the team is past the fortieth unit.
• Wipe down, fit glides where they ship loose, place at table: 1 to 1.5 minutes per chair.
• All-in: about 6 to 8 minutes per chair, so a 140-seat restaurant takes 15 to 19 hours of two-person labour, or two full days with 20 per cent added for the first-day learning curve.
• Waste: 0.9 to 1.4 kg of carton, plastic and foam per chair, which is 130 to 200 kg on a 140-seat job. Book the skip before the truck arrives.

Re-torque schedule and the spares bag

Joints relax. Plan for it rather than discovering it in month four.

• First check at 7 days in service, second at 30 days. Clamp load drops 5 to 15 per cent in that window as felt glides and seat pads compress.
• After that, every 6 months in normal service, and every 3 months for 24-hour operations or high-turnover canteens.
• Shipped equipment: one hardware bag per chair holding every fastener for that chair, one spare of each size, the correct hex key and a printed exploded diagram.
• Loose allocation: 0.5 per cent extra hardware bags per container, unlabelled, for the units everyone loses something from.
• Stripped holes in wooden frames take about 15 minutes with a hardwood dowel and an oversize insert, against 40 minutes plus freight to swap a frame.

The parts we keep in stock and the quantities advised per 100 units are listed on the commercial restaurant chairs, and the hardware packs issued with an OEM programme are described on the OEM hardware specifications.