We were fortunate today to come across an orb-web spider weaver her web under perfect lighting conditions and so, not being any sort of a hurry, decided to take the time to make a video recording of the fascinating process.
When we arrived, the framework (spokes and guy-lines) were already in place and she was going round and round adding the spiral that will trap her meals. The whole process took less than 15 minutes for a web about a foot in diameter. The precision is fascinating – and note the way that as she links each line of silk to the spokes one of her rear legs stretches out to grab the previous circuit of silk and tweak it so that the spacing is maintained accurately.
The part of the process that we missed, laying out the radius-thread framework is shown very well in a short graphic at this site … http://science.howstuffworks.com/zoology/insects-arachnids/spider5.htm