Cutting Plywood
No matter what kind of woodworking you do, at some point you're going to be using plywood. Whether you're building cabinets and using commercially available plywood, make your own veneer, or buy veneer to apply to a plywood substrate, sooner or later you're going to have to deal with cutting plywood.
3 Circular Saw
The biggest problem woodworkers have with cutting plywood, especially when cross-cutting, is that the veneer often splinters out along the cut line. So much for that expensive piece of veneer!
Here are some ways to avoid this:
Let's first look at the tools used to cut plywood, both for cross cutting and ripping. Large 4 x 8 sheets of plywood are most often ripped using the table saw. When ripping or cross cutting on the table saw the good side should always be facing up. This action alone will prevent the majority of splintering on the good side. To be sure of this though, two things should be done to your table saw. First, you need to be using a sharp 40 tooth combination blade, (my favorite is the Forrest Woodworker II) or a high alternate bevel grind blade, a specialty blade designed to cut melamine and veneered wood without splintering. Second, your table saw needs to be tuned up. By this I mean that the blade needs to be parallel to the fence. On the side facing up, if you're only getting tear out on one side of the blade, this is probably the problem. If you're getting tear out on both sides of the blade, your blade is wobbling due to being bent, or the arbor isn't running true. It helps to have a dial indicator to tune up your table saw.
For cross cutting large sheets of plywood, more times than not, I will use a circular saw. If you think of the circular saw as a upside down table saw, it will make sense to make sure you cut with the good side facing down.
Here's four tips for using a circular saw to get a clean cross cut on plywood:
1) The same blade considerations we talking about for the table saw apply to the circular saw.
2) Score the plywood first by setting the height of the blade just deep enough to score the top veneer. Then go back and cutting all the through. This method works very well if you use a fence so you can make the exact same cut twice. Free handing a cut like this won't work.
3) A method I like to use to help prevent splintering on the bottom side when using a circular saw is to use a backer board. Use a sacrificial sheet of cheap MDF underneath your plywood. Lower the blade to just cut below the thickness of the plywood. The MDF will support the fibers of the veneer, keeping them from tearing out.
4) Another trick is to use a strip of painters tape or masking tape along the cut line. The tape acts like the back board in the previous method. A work of caution here. Don't use tape that is real sticky, it will end up pealing up the wood fibers underneath, exactly what you were trying to avoid. Which ever type tape you use, be sure you remove it as soon as the cut has been made to prevent it from melting to the plywood from the heat of the blade.