Join Date: Oct 2012
Location: Eastern Kentucky
In my experience, using a square all the way around a 4x4 to connect all the lines only works about 1/2 the time due to inconsistencies in the 4x4 sides slightly throwing the square off with each line. You end up with the last line missing the first line by 1/8 inch at times. This absolutely cannot be relied on every time.
Start out with a saw blade set to a perfect 90* to the saw foot. I usually make one mark on one side all the way across, maybe one more on an adjacent side also, using a speed square. Anymore marks just ends up doing the above mentioned misalignment. After this, I make one cut with the circular saw, then rotate the 4x4 so the next side is up and already 1/2 cut from the first cut. I just follow the rest of the line and complete the cut. Then rotate once more and do a third cut. I generally don't even need the third side marked, I can just complete the cut by following the rest of the kerf from the last cut. A third mark is liable to have been off by this point anyway, and just serves to make me think I missed it if it's there and was off. I just lean over the wood and watch the blade come out exiting the first initial cut, which assures me that I got it right even before I see the final result.
3 total cuts and it's done. Usually ends up totally flat on the end but once in a while it might be off. Usually I'm building a deck with 4x4's so I can hide the ends if they're off any. If it needs correcting, I can just sand where I made the third and final cut since that is where any mistake almost always is. Most times it comes out just fine. One thing that might be causing problems for you is how well you support the wood while cutting. If it can fall away as you finish it, it's not right. Across two saw horses and cutting in between is wrong. I'd sooner use one horse only and have it longways on top of it (if possible that is, I built horses for this, some don't have a wide enough top though, attach a flat 2x6). The cut can be ruined as the wood is removed and allows movement that can bind the blade. I prefer it totally clamped down, supported full length, and then cut. Much better results then.
Otherwise, a sliding miter saw can be used. Or two 2x4's, each cut to same length and then glued/screwed together.
I've also found combination squares to be inaccurate also. They have too much play. I prefer engineer's squares and speed squares, carpenter framing squares, anything fixed and non adjustable.
One more thing you might try. Make two adjacent marks, one on top, one down the facing side to you, and then start slowly and use a Japanese pull saw. It will take a few minutes but not nearly as long as you think. The cut will be superb when finished. I got one from Home Depot for $10 and I'm amazed at how accurate, and fast, it cuts.
Last edited by Duane Bledsoe; 01-21-2013 at 01:29 AM.