Nut and feder splicing: what it is used for and how it is done

The tongue and groove joint is one of the oldest joints being used in the walls of wooden houses or to the floors. In houses, the planks were laid horizontally, one on top of the other (on the small side), forming the wooden wall. The ends of the planks entered a trench dug into the posts at the ends of the houses. When the wood dried out and shrank in size, the planks would be re-laid, 'falling' over each other so that no gaps remained in the walls for the wind to blow through. The gap appeared only at the top, but that part was protected by the eaves, which were very common in old houses. The gap could easily be closed with another plank, completing the wall. But this is not the main area where the joint is used. Let's find out more about nut and feder jointing.

What is nut and feder blending and how is it done

The name nut and feder comes from German. German and Austrian tradition required apprentices to go out into the world and make a living from the craft they learned for at least a year (some sources say 3 years) before becoming a craftsman and having their own workshop. This tradition of the "Travelling Horses" is now revived and we can meet them at the Sighisoara workshops. This is how they came to us in the past and some terms have been taken over from them in the field of wood (baiț, holzsurub, țicling). The Romanian name for the joint is lambă and uluc.

Joinery was used in the past to make large wooden panels. The appearance of plywood and chipboard has led to these panels being replaced by the new products and to less and less use of the joint.

To put two pieces of wood together using this joint the edges of the wood are machined lengthwise. It is also possible to join all 4 sides, but this is done much less frequently. Long pieces of wood can be joined together to form a compact, large panel.

The joint itself involves a groove (nut or tongue) made in the edge of a plank, along its entire length, which fits perfectly with a profile (feder or lamba) made in the edge of the plank to be joined. As the panels are made from a succession of such planks, each one has an uluculum on one edge and a lamba on the other. It is the fixed lamella joint.

There is also the possibility of joining with mobile flap. In this case, the planks have on both edges a nut in which a narrow piece of wood fits perfectly, the thickness of the nut and the width slightly less than the depth of the two joined nuts. This way the plank will fit perfectly into the two recesses in the sides of the planks, forming the panel. In both cases (fixed or movable battens) a deeper nut gives better joint strength in case of wood shrinkage.

The joint is usually removable, the elements are not nailed or glued. As large elements are used the dimensional variations of the wood can be significant. Not being stiffened by fixed elements the wood will be able to move and cracks will not occur.

The blades and the pitchers can be joined either manually, with hand tools or routers, or on industrial machines and CNCs, using cutters with special profiles.

Where it is used

The combination of nut and feder is specific flooring and floors. The wooden elements have factory milled millings and are removably joined so that they can be rearranged over time. Shrinkage is normal for parquet or solid wood floor elements. They should therefore be left "loose". After some time, if holes have appeared between the elements, they can easily be re-laid (re-tanned). If they are glued or nailed together, it will be very difficult to reposition them and there is a risk of cracks.

Laminate flooring has a similar type of joint to the nut and bolt joint, but creates a more fixed joint. It's called a click joint system - from the sound it makes when assembled. The nut is larger inside than the opening and the feder is forced in, making it impossible to pull the elements apart in opposite directions.

The advantage of the nut and bolt joint on the floor is that the static force that the furniture exerts on the floor is taken up by the other elements and is equalised across the entire surface. This ensures the stability of the floor.

It is also used in the manufacture of furniture and is considered an aesthetic joint. In this case the joint is stiffened by gluing, but here the elements are smaller, reducing the risk of cracking. The groove and profile can be made with a swallowtail, making the combination even more attractive. Also to improve the aesthetics, the horizontal and vertical elements are joined together in a nut-and-bolt fashion.

It is also used in construction, when cladding houses with nut and bolt elements or mounting wood fibre insulation boards. in the case of insulation with nut and feder bonded fibreboard decreases the risk of thermal bridges.

It can also be used outdoors, to join fences, to clad swimming pools, to create gazebos or terraces.

Joining is not specific to wood. It can also be used to join tile and ceramic tiles, plastic or metal elements.

Types of such joints

Making the joint with separate flap is not the only "variation on the same theme". The joint can be double, with two fillets and two pillowcases on the edges. This makes it much more fixed, more resistant.

Another option is to make both a nut and a feder on each edge, the lengths being different. This type of joint provides greater resistance to twisting.

The nut and feder joint with counter profile is used to hide the joint when fixing the paneling with hidden nails. The profile is designed to hide the effects of wood shrinkage.

There are joints with continuous nut and interrupted feder. Basically the joint is made from place to place, the rest of the edge is free. It is a useful joint where there are large dimensional variations and an increase in the feder would lead to forcing of the joint and cracking. It is, however, a less solid joint.

As opposed to the joining in swallowtail or the one with a log and notch, the nut and feder joint is not specific to furniture production and not widely used. However, it is quite common and can be used successfully when we want to make a table top out of planks. It is a stronger joint when used horizontally, as evidenced by its use in flooring. When used vertically, its strength may need to be increased with glue or nails and screws.

If you are thinking of using it to make various objects or cladding I hope the information in the article will be useful. Good luck!