You can use an exacto small miter box and a hobby razor saw,
or one of these cut off saws if you do a lot of them
Item # 42307 harbor freight
I have the old version from a couple years ago, different color plastic. I have seen and examined a number of different brand names They all appear to be made by the same company the only difference other then the colors is a higher price.
I needed to cut a couple hundred short sections of tube and wood pieces. It worked well enough for the price. $27.99 on the web site. It uses a 2" dia fine tooth blade but I have also used the 2"dia abrasive wheel.
Or these jeweler tubing cutter fixtures.
you can get these and other thing at modeler tool sites like here
http://www.micromark.com/saws-and-miter-boxes.html
Only connection is I own or have used one or more of them over the years, and a satisfied customer.