When I got started with woodworking and amp building, cutting a straight line was the most intimidating part of just about any project. Not having the space or justification for a table saw, I tried more than one way of following a line with a jig saw and circular saw before I found something that works for me. Now I do not shy away from ripping boards to specific widths quickly and it only took some scrap and ingenuity.
What I found was a really simple circular saw jig made of a three or four inch wide 3/4″ board and some ten or twelve inch wide 1/8″ sheet. If you can find a board with a straight edge (preferably machined right from the lumber yard), you can cut a straight line. The jig is simply the 3/4″ board glued to the overly-wide thin sheet. You then zip your circular saw down the board with the shoe pressed against the straight edge to cut off the excess 1/8″ material. Viola. You now have a jig that will always cut just as straight as the board you used to build it.
Here’s a picture of my jig (rebuilt this weekend because the old one was getting chewed up):
To use the jig, I mark the piece that will be ripped or cross cut in two places and then connect the dots with the now arrow-straight edge of the 1/8″ jig base. Clamp it down and then let the circular saw ride against the thick portion of the jig. Because the saw’s shoe doesn’t change width, it will always faithfully cut along the edge of the 1/8″ material, provided you are making sure it is following snug against the thicker board. Straight cuts don’t get easier than this and I’d wager that this is at least as fast as setting up a table saw for every cut.
As far as measuring, I’ve always got a combination square near at hand (great for marking holes in top plates, too). This makes setting a repeatable distance from an edge quick and easy.
If the thought of table saws and messy cuts prevents you from tackling your next amplifier or speaker project, hit the bargain bin at the lumber yard and whip up a simple jig. This hobby doesn’t require expensive equipment if you get clever with the tools on hand.