A Razor Saw and Mitre Block.
The saw can be fitted with a number of different saw blades, differing numbers of teeth per inch and slightly thicker blades do different jobs.
I use a coarser blade to cut Nickel Silver rail section than say plastic components. Available from most tool stands at Exhibitions, this tool gives ,at least, a clean square cut.
This is helped by its close friend-The Mitre Block. With pre cut slots, usually at 45 and 90 degrees, the blade of the saw is guided to produce a accurate cut every time. To aid this i usually clamp the workpiece in place before letting loose with the saw.