What tools do I need to cut perfectly straight edges with a circular saw?

[Fusion916]

Using a circular saw, what tools do I need to cut perfectly straight for speaker boxes? Also, what circular saw do you recommend?

[ChicagoJTW]

You need a clamp-on aluminum straight-edge. They look like this: All-In-One Low-Profile Contractor Clamps, New & Improved! - Rockler Woodworking ToolsIt has to be long enough to reach across the stock. Straight-edges are available in lengths up to at least 60 inches. Be sure to factor in the actual kerf line, don't just use the alignment guide on the saw.

Which saw? Any quality circular saw that's light enough for you to handle. I have a titanium Porter & Cable that works extremely well. It's a matter of feel.

[Cal Weldon]

Buy a good quality saw and a thin kerf carbide blade. Get a couple clamps and make a sawboard. To make the sawboard it helps, but isn't mandatory to have a straight edge.

Great Jigs: The Sawboard | Tom's Workbench

EDIT: What JTW shows works also.

[ChicagoJTW]

Oh yeah...you can also simply nail a straight-edge to the plywood. Most long wood isn't perfectly straight, though.

[Cal Weldon]

I should have said it helps to have a metal straight edge. The way I wrote it, it sounds like I meant a straight edge on the wood.

[buzzforb]

Take an 8" or wider piece of 10' x 3/4" clear pine available at most home improvement stores. Whatever width you need. The nicer and straighter the board you get, the less chance you will have of replacing it. Oak is nice. Buy or rip two smaller pieces about 1.5-2" wide and the same length. Create a track for the saw. Place the saw in the track, blade up. 6-8" from the end, start sawing by dropping the blade down and cutting throgh your track. Then rip a line following the track down ro the otjer end, leaving as much roomthere as inthe beginning of the cut. If you have chosrn your wood well, you now have a jig that will rip straight cuts with no chance of the back end of the saw drifting. Drift is thd main reason it is difficult to rip straight lines with a circular saw, regardless of blade or saw. Better blades help, but the jigcost same price and you can get cheaper bkades from then on.

[Cal Weldon]

So if I am reading you right, you have created a double sawboard with a slot for the blade but not cut through the to ends or you would have two sawboards. On the surface that sounds good but how do you align the slot with the intended cut line? Also, it seems that this might be a difficult build to have the close tolerance on the alignment of the track. It can't bind and it can't be loose either.

[overtheairbroadcast]

To get that straight edge?

Well, I have the second heaviest, nastiest, powerful worm drive circular saw on the planet. I then swap out the regular Irwin blade (the newer expensive ones are nice as you don't lose teeth as often -- only saw blade that I haven't lost a tooth yet) and use a nice Diablo blade with an amazingly thin kerf and lots of teeth for finishing; though the Diablo blades are more for construction, it is a far cheaper route than going with the Forrest or Freud blades (especially when the Diablos are on sale). I grab the very old 6-foot long metal ruler my uncle gave to me and a couple of low profile C-clamps (with added rubber pads). Then I set the blade height to just get through the thickness of the wood.

Then the best part. I drop the wood onto a couple of sheets of blue styrofoam insulation (I have lots of it from a friend who bought too much) and that is on the only flat part of the garage floor. Clamp down the ruler onto the wood, check with the saw blade, mark the cut with pencil, mark the ruler in case it moves, make doubley sure with an adjustable square, and we're good to go. Measure, layout, measure, and cut once. Nice and slow means less tearout and chipping.

Just in case, why worm drive? I had a "Craftsman Industrial" sidewinder for the longest time and when that started to burn out from a good 15 years of use, there was a RIGID wormdrive one on sale. When this one gets burned out, I'll buy whatever is strong and cheap. Great thing with wormdrive is that I can see the blade easily without craning my head over the body of the saw and dang, the motor never once has sounded like it was under load. Bad thing, it takes some time getting use to the weight.

Good lighting also helps.

[buzzforb]

Originally Posted by Cal Weldon

So if I am reading you right, you have created a double sawboard with a slot for the blade but not cut through the to ends or you would have two sawboards. On the surface that sounds good but how do you align the slot with the intended cut line? Also, it seems that this might be a difficult build to have the close tolerance on the alignment of the track. It can't bind and it can't be loose either.

Thats correct. You can see your crows feet, marking line through the cut. I can assure you that using this technique, the cheapest saw and blade will cut like a worm drive and the finest frued blade. Thats an overstatement, but you get the point. Drift. The back end of a saw blade is going to follow the pathof least resistance. Even cutting plywood, it tends to drift to the open area. The nicer and toughr the substrate, the more likely it will happen.

[lizhi3amorphous]

i think you need amorphous cutting cores or retangular c core for the circuit