circular saw jig question

[lielec11]

Hello all. I am a relative newbie in the wood working world. I have completed a few projects (mostly floating shelving and a craft desk for my wife). To date, I've been able to knock those projects out with my table saw.

I just started working on a built in entertainment center using plywood and I am forced to breakdown the ply using a circular saw before I can safely rip/cut on my table saw.


I am having major issues cutting my plywood straight using the circular saw. I have cut a few pieces that aren't square and end up 1/8"-1/4" off on one end of the board. I created a circular saw jig using a straightedge but my question is, how do I know exactly where to line it up on my board if the board isn't square? How do I know that the jig will be straight when I line it up on my piece?

Thanks in advance.

[JGrout]

Hello all. I am a relative newbie in the wood working world. I have completed a few projects (mostly floating shelving and a craft desk for my wife). To date, I've been able to knock those projects out with my table saw.

I just started working on a built in entertainment center using plywood and I am forced to breakdown the ply using a circular saw before I can safely rip/cut on my table saw.


I am having major issues cutting my plywood straight using the circular saw. I have cut a few pieces that aren't square and end up 1/8"-1/4" off on one end of the board. I created a circular saw jig using a straightedge but my question is, how do I know exactly where to line it up on my board if the board isn't square? How do I know that the jig will be straight when I line it up on my piece?

Thanks in advance.

The factory edges of sheet stock are square. 

I have two cutoff straightedge fixtures  this one is 8 feet long 

This one is 4' long 



So if you measure out the size of the panel off the factory edge  and mark with a pencil at each end then lay the straightedge directly on the pencil marks and clamp it to the work your cut should be straight and parallel  do the same for the cross cuts

Joe

[lielec11]

I just made a similar jig. However the issues is before the jig I made some cuts so the there no longer exists a factory edge to use as my reference. This is the basis of my question. Is there a way to accurately make sure my jig is straight when the board doesn't have a square edge?

I'm basically trying to save myself from going to buy another piece of plywood by salvaging this piece.

[Jlivingstone]

I just made a similar jig. However the issues is before the jig I made some cuts so the there no longer exists a factory edge to use as my reference. This is the basis of my question. Is there a way to accurately make sure my jig is straight when the board doesn't have a square edge?

I'm basically trying to save myself from going to buy another piece of plywood by salvaging this piece.

If you have a square, just line the square up along one edge of the plywood and then line your jig up against the square.

[lielec11]

If you have a square, just line the square up along one edge of the plywood and then line your jig up against the square.

Wow I feel really stupid right now... such a simple answer staring me in the face. Thank you!

[Papa Jim]

Wow I feel really stupid right now... such a simple answer staring me in the face. Thank you!

Don't beat yourself up. We were all there once---and sometimes we even go back!

[Alan S]

You have it figured out now, so are fine.  Note that your initial question really was "how do I set up for a cut square to a straight edge?"  You accidentally asked about cutting "straight" rather than "square".  You were clearly understood, so what's the big deal?   Just that as soon as you heard the word "Square" you knew the answer.  Sometimes posing the question as carefully as possible will help to lead you to the answer.

[sweensdv2]

Wow I feel really stupid right now... such a simple answer staring me in the face. Thank you!

Don't beat yourself up. We were all there once---and sometimes we even go back!

Aint that the truth. Had one of those moments myself just this morning.

[Bill Holt]

lielec11, the smart thing you did was to ask the WoodNet fo1k.  Welcome to a great place, where a great group are eager to help.  Someone may jerk your chain now and then but, in my experience, someone always has a helpful answer.

[Steve N]

If you have a square, just line the square up along one edge of the plywood and then line your jig up against the square.

You can use the square to sort of locate where you want to place your cleat. but allow plenty of excess ply past where that saws blade will cut to. Also allow plenty of ply on the other side of the cleat if you plan to use clamps to hold the jig in place. That off side doesn't need to be straight BTW, just ample space for clamps, so they don't interfere with the saws progress as it goes down the jig. The advantage of extra material on the cutting side of the jig is, even if your straight edge turns out to be not so straight after all, when you cut the excess off the ply off it won't matter, that outer edge will be exactly the same distance from your cleat, which is the functional working part of this jig. Crooked isn't in the equation, just an equal distance from cleat to edge.



Two other things I do using that type of jig when cutting plywood that you want to be CRISP on it's edges.

1) put down a thick piece of that styrofoam, insulation foam board under your ply, the blade will bury into that and any bottom side tear out will occur on the foam.

2) On the top side figure out where your cut will be, and end to end cover the ply with a band of painters tape, you will cut through the tape, but it makes for something like a ZCI on your table saw.

Both sides will have crispy edges. Do a trial run before you actually cut, and make sure you understand the dynamics of pushing the saw forward, while also holding it tight to your cleat. The number 1 complaint I have heard is that evidently some folks have a hard time holding the saw to the guide cleat???

Joe has a carpenters background, and so do I. I think we take sawing with a circular saw for granted maybe?