It takes me about two minutes to build and assemble one ring. For a long-sleeved chainmail shirt with 8mm rings, I need about 30.000 rings. That equals 1000 hours of work. If somebody was doing this 8 hours a day, he will need 125 days. Without working on the weekend it will take that person a bit more than 6 months to finish. However, this does not represent the time a customer would have to wait for chainmail. If chainmail is produced in a workshop, many workers can team up and start with sheets of chainmail that they have prepared in advance. Thus it would take one or two weeks to build a custom-tailored chainmail shirt. I assume it was done this way in the middle ages.