Milling sticks : Evolving methodologies to fabricate complex traditional Japanese timber joints for use in light timber structures

Abstract

The role of a carpenter in traditional Japanese architecture is as much an architect as a craftsman. Japanese joinery created by miyadaiku carpenters (carpentry techniques using interlocking wood without nails) allows timber connections to be resolved by sophisticated joints without relying on mechanical fastenings. This approach to timber design has been largely lost with the adoption of mechanical fastenings such as nail or screw connections, especially in the construction of structures with many small timber members. Essentially, this is the result of the expensive labour cost associated with making timber joinery, leaving this craft to be the reserve of high-end furniture; it is no longer seen in the realm of 21st-century building. Sophisticated timber joints are still used in structures with large timber members, costing thousands of dollars. Using a CNC (computer numerical control) to mill the joints accurately with timber of this scale, the time and set up of the CNC milling is justified by the cost of the member being cut. However, a gap in the application of this technology exists regarding small timber members, costing a fraction of what larger members do. As a result of this, the cost to set up the CNC cannot be justified, and screws are used. The question focusing the research is ‘How can simple three-axis CNC milling be utilised to fabricate traditional Japanese timber joints, creating viable timber-to-timber connections on small members?’ and secondly ‘How might this methodology be applied to a live project?’ Research into this field has been undertaken by previous timber structures thesis supervised by Andrew Barrie, such as Dylan Waddell’s Shadow Pavilion (2019), which devised a jig to hold and consistently cut many small pieces of timber by locating sticks on the CNC. This massively reduced the set-up time associated with milling each stick. Kanade Konoshi’s Watari-Ago Shelter (2020) evolved this jig using toggles to make moving the stick within the jig even faster and more accurate. Both projects successfully milled one face of the timber to create lapped and cog joints; the issue is the limitation of what type of joints can be fabricated when only one face of the timber is cut. In this thesis, a new jig methodology is devised to cut multiple face of the timber so that more sophisticated and complex joints can be fabricated. To interrogate and test the methodology, a 12m2 forest classroom constructed from a lattice of small timber members, connected by Kashigi-orie joints, has been built for a client in Papamoa. This serves as a built example of how the technology can be applied to live projects, dispelling the notion that structures of this scale and budget must rely on mechanical fastenings.