Manufacturing of curved staircase elements

Curved sections are often used in wooden stairs. Curved handrails and curved bowstrings allow you to give your staircase your own individual and unique look. It is extremely difficult, but possible, to make bent staircase elements at home. This work requires a lot of patience, but the result can be a product that will decorate the architecture and interior of the house. For centuries, woodworking craftsmen have used bent wooden elements in joinery, achieving significant skill in the process. There are several methods for making bent wood products that are completely different from each other..

Method one consists in cutting out of a solid piece of wood along the required contour according to the template of a wooden element. Despite its apparent simplicity, this method has significant drawbacks. Wood with straight fibers, in places of bends, can split along the fibers, which significantly affects the strength of the manufactured product as a whole. In addition, this technology entails increased wood consumption.

Method two, used for many centuries, it consists in softening wooden products by boiling or steaming in metal molds. For this, a piece of wood is placed in a container with boiling water and kept for several hours, keeping the water boiling. After that, in places of bends, mechanical stress is created to give the structure the required shape. For this, all kinds of devices are used, reminiscent of pipe bending machines. The curved element is fixed in this position until it is completely dry. After drying, the bend remains with the clips removed. The fibers of wood bent in this way take the form of an element and its physical and mechanical properties practically do not differ from a straight piece of wood. If it is necessary to make several identical bent elements (ladder bowstrings or handrails), in order to maintain the identity, “bent” should be performed in conductors specially made for this purpose. Otherwise, it will be difficult to achieve full identity..

Third method consists in sticking thin strips of wood on a wooden block in places corresponding to the convex part of the element. Multilayer gluing with subsequent machining allows you to give a wooden element any, even the most intricate, shape. This method is rather laborious and time consuming, especially in home workshops..

Modern technologies make it possible to obtain glued wood structures (DKK) of any shape and length. They usually consist of two or more layers of sawn timber, glued together in such a way that the fibers of all layers are absolutely or approximately parallel (Fig. 1).

Fig. 1. Making curved parts

For the manufacture of DCC, pine or spruce is most often used. If it is necessary to obtain the texture of valuable wood species, they resort to veneering or veneering. In the manufacture of DCC, lumber of maximum thickness is used for straight sections or curved sections with a radius of curvature of 6 m or more. For all other curved elements, the thickness of the sawn timber should not exceed 1/50 of their radius of curvature. Drying of materials is a very important aspect of the DCC manufacturing technology. It largely determines the operational strength of the bent element. In order to avoid the appearance of internal stresses in the elements, it is very important that the layers to be glued have the same moisture content or that the difference in moisture content of the layers does not exceed 5%. At the same time, modern technologies have the drying methods we discussed earlier. Ladders made of DKK elements are not inferior in their physical, mechanical and aesthetic qualities, and in many respects they are superior to products made of solid wood.