We found this video of Minnesota carpenter and deck builder Brian Campbell making quick work of crosscutting 6x6 timbers using a Makita 16-inch circular saw. Big saws want to go in a dead straight line, which makes it tricky to cut the line you want to cut. While this seems counterintuitive, it's not, as with a standard size circ saw you actually make frequent slight adjustments to stay on the cut line. That's a lot harder to do when you have a big blade embedded in a cut. To deal with this problem, Campbell uses a homemade jig.
Campbell says, "The jig really helps keep that monster cutting straight, which is very important with a blade that big (the most minor twisting causes it to bind). The jig features a fence, of course, and a table of MDO for smooth sliding along (timbers can be rough) and both infeed and outfeed support to keep the cut running true. The jig would work well with 10-inch Bigfoot saws too. The bottom cleats that grip the 6x6 were sized for the largest timber in my pile (undersized timbers required the use of tapered cedar shims to hold the jig snuggly). "The Beam Saw is an interesting saw to use. The motor on this saw is about the same size as those found on 'normal' circular saws. It takes a few seconds for the blade to get up to speed, then it relies more on inertia of the spinning blade rather than raw power to cut. Inertia of that massive blade also helps prevent kickback — it tends to slowly bog down and bind rather than kick. This saw gives the user more feedback than most saws and the jig does help keep the saw from binding too." Campbell's Web site is www.basswoodcarpentry.com