of machinery. Model engineers often economise by making items of tooling themselves. Although traditionally a manual hobby, that is, one that relies on the model engineer hand-making the parts with the assistance of manually operated machinery, computerised tools are becoming popular with some model engineers. Designs are now often produced with the aid of CAD software. Some model engineers use 3D CAD software to build the model in virtual space before commencing on the physical model. Such CAD software also interfaces with CNC machinery, particularly milling machines, of which an increasing range is now aimed at model engineers and other 'home shop machinists', making it possible for some model components to be manufactured under computer control. 3D printing is another emerging technology for model engineers to explore. Model engineering continues to expand by incorporating new technologies including laser cutting, 3D printing and embedded electronics establishing more and more common ground with the maker movement, these computerised pursuits are a sub-branch of model engineering and are not followed by the majority. Model engineering kits Kits of parts offer a shortcut to the traditional method of building. Kits fall into two categories, machined and unmachined kits. Unmachined kits usually consist of drawings, castings, stock metal, and possibly fasteners and other fixings necessary to complete the model. They require machining facilities to complete and often also require additional components and raw materials. Typically the minimum machine requirements are a lathe, drilling machine, and possibly a milling machine. A good level of knowledge about machining is necessary to successfully complete these kits. Machined kits are a set of parts that are fully machined and only require finishing with hand tools, painting, and assembly. Workshop machinery is not required. The kit will typically contain all the parts necessary to complete the model. These kits require a lot less work than an unmachined kit, but are very expensive and choice of subject matter is limited. Information sources for model engineering There are many books, magazines and internet forums about model engineering. Magazines such as Model Engineer and Live Steam remain the main source of detailed designs and plans (in addition to carrying news items and discussion of products and techniques). These detailed designs and plans contain instructions and drawings sufficient to build a particular model. In the pages of magazine back-issues, hundreds of such designs exist for all sorts of models. Many of the plans are