WARNING: FR4 boards are made from fiberglass, the dust from cutting it isn't overly good for your health. The particles are sharp and stick in your lungs, it gives you something like what you get from asbestos; silicosis (breathing in dust from sand-blasting) etc. Same goes for drilling holes. It'll take a while; the problem is that unlike most things that take a while to build up (e.g. lead poisoning) and get flushed from your body in the meantime, dust like this will happily sit in your lungs forever. If you're susceptible you'll find out in 20 years. Just cutting the copper, and cutting less of the board, will put out less dust. Some people prefer to 'score & snap', or cut it with shears. That's not always possible if you're cutting slots in the boards (HV isolation etc) or funny shapes. Keeping the dust collected, wearing a mask, working wet (e.g. tile saw) are probably all fairly smart things to do.
Safer board types are FR-2, FR-3, CEM-1, or CEM-2 which are cotton and epoxy. CEM-3 and higher contain glass. These types are difficult to find.
Vinyl Tile cutters. Richard D Heiliger says: "this is the best way to cut FR4 I have found, straight smooth edges, near no effort to cut 1/16 board, board does not skew either, has a cast aluminum frame, the blade is pinned at both ends giving increased leverage and keeps the blade from wandering and skewing the cut."
Shears PCB stock can be cut with large handheld shears such as Wiss offset aviation snips. Beverly shears are better. Shearing is nice because it avoids the contamination of the area with fiberglass particles which are extremely irritating to the skin and a serious danger in the eyes.
Saws Hacksaws, circular saws, and just about any other sort of cutting tool can be used to cut PCB stock, but the glass based boards (FR#) will dull a cutting edge quickly and the particles are extremely irritating to the skin and a serious danger in the eyes.
Tile saws are designed to be run wet, and the water can help to contain the particulates. Very fine blades (sold for cutting gem stones) are available.
Milling professional PCB houses typically CNC Mill stock with a lubricant which collects the particulates and keeps them out of the environment. More: Printed Circuit Board Milling Machines
V Scoring deeply scoring the board on both sides can allow the board to be "snapped" with a quick motion while half the board is supported on a strong, flat surface. Many users report a very ragged, rough edge.
score depth
-- Ed Valentine on 2001-08-07 Electronics Manufacturing Solutions
Assuming you are going to do a manual breakaway of the boards, I recommend a final web thickness of 0.012" with 30 degree cutters on FR4. If you are using mechanical/machine separation you can go slightly thicker. The thin web thickness allows for easy, manual breakaway with minimal potential damage to the components and the solder joints.
Gary Ferrari on 2001-08-07
Please take note that your respondents have discussed the material "remaining" after the scoring process. Your drawing should not indicate a depth requirement, but the amount of material remaining.
Pocket Guide to Excellent V-Scoring http://www.accusystemscorp.com/FAQ's%20-%20Index.htm ``useful'' -- recc. Bill Brooks 2001-08-07 PCB Design Engineer http://home.fda.net/bbrooks/pca/pca.htm
Scroll all the way to the bottom of the "Reflow Skillet tutorial" http://www.sparkfun.com/commerce/present.php?p=Reflow%20Skillet for some nice close-up photos of a "scored" PCB panel.