# Advise on cutting plywood with circ. saw



## Ronnie1a (May 24, 2009)

My project calls for cutting several pieces from 4 x 8 1/4" plywood sheets. My table saw is too small to start with the whole sheet. I bought a steel guide which clamps on the plywood (4' long) for my 7 1/4" circular saw to follow but my limited experience in the past was "ugly" at best. My questions:

Does it matter which side of the circular saw goes against the guide?

No matter how slow I go I cannot get a clean cut. Looks like a giant tear. Would putting masking tape over the cut before I make it help?

Should I bite the bullet and just make oversize cuts then re-cut on the table saw?

Same question about tape on the wood when using the table saw.

Any other advise/tricks on making the initial cuts from the 4 x 8 sheet?

Thanks in advance for your responses.


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## cabinetman (Jul 5, 2007)

You could use your metal straight edge, but it's hard to clamp, and doesn't have much height for a guide. You could make yourself a "T" square type of* jig like this*.

It's easy to clamp down, and works like a square. Your first cut will cut off the right leg right where the saw cuts. So, your next cut and all those thereafter with the same blade, all you do is make your mark for the cut, and set the edge to the mark...and cut. 

The saw is easier to guide when using the right side of a guide, and the left side of the saw base. Cut your plywood with the good side down. For that thickness, or for good smooth cuts, use a 40T carbide tipped blade.









 







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## ACP (Jan 24, 2009)

I agree with what cabbie said. I would also recommend buying a good blade. I use a 40T Freud blade for my 7 1/4". Those blades for the circ's are not too expensive, but you need a good one just like a table saw for a good cut. Masking tape may help reduce tearout too. Some folks use it. I bought a sheet of that pink foam for insulation and I like to lay the plywood on it for my cuts. This supports the wood throughout the cut and gives a small measure of backstop for the cut too.


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## Dave Paine (May 30, 2012)

I use a metal straight edge which is specifically designed for such cuts with a circular saw or jigsaw. This is an aluminium extrusion and special clamps to the underside of the plywood.

If your clamps are above the plywood, this will dictate which side to clamp. Whichever side you clamp should not affect the cut - as long as the full sole of the saw is supported.

You do not say if the tearout is top, bottom or both sides.

As others said, good side down, and set the depth to be just below the wood. The comment on cutting on something sacrificial does work. Insulation board, styrofoam etc. Even another piece of wood or plywood.

On the top side masking tape can help to minimize tearout. Scoring the line helps, but you have to score exactly where the blade edge will cut.

As C'man said a good blade is important. I was having a problem with my edges looking rough. I looked at the blade and although it had only been used a few times I had a chipped tooth. I replaced the blade and solved the problem. The edge is better but the circular saw cut is not going to look at smooth as a table saw cut even with a good circular saw blade.

For the top side tearout, you could also make a zero clearance attachment. Cut a piece of e.g. 1/4in plywood which is at least the length of the sole, perhaps longer and at least as wide as the sole.

Attach with double sided tape. I have the turners double sided tape which holds very well.

Support the saw on a bench/stand so that the blade does not contact anything. Raise the blade and then start the saw and carefully lower the blade to cut through the plywood.

Between the zero clearance for the top and sacrificial for the bottom you should be able to solve your problem.

Plan B as you said is to cut wide and then trim on the table saw. Works well, just extra effort.


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## Pirate (Jul 23, 2009)

I use a shopbuilt zero clearance guide, and a sharp blade, and have great cuts.
The zero clearance guide, makes it much, much, easier to line up the guide. I also have a clamp on guide, which I never use anymore. 
I love that many shop built jigs work better than store built ones!


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## Ronnie1a (May 24, 2009)

*Thank you for your responses*

Your advise is much appreciated.


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## mobilepaul (Nov 8, 2012)

Ronnie1a said:


> My project calls for cutting several pieces from 4 x 8 1/4" plywood sheets. My table saw is too small to start with the whole sheet. I bought a steel guide which clamps on the plywood (4' long) for my 7 1/4" circular saw to follow but my limited experience in the past was "ugly" at best.
> Thanks in advance for your responses.


Late to the party, here, but I would make a sled for the circ saw AND get a good blade. HD sells a Diablo for 16-20 bucks that would give you smooth results.

I went to HD and purchased a sheet of their 1/4" luan and cut a 4" strip off a good 8' edge. It's the edge that matters, not your cut. Then, cut a 12-16" slice 8' long. This cut doesn't really matter either, just try to keep it as straight as possible. Take the 4" rip with the factory edge facing inward and glue it well to the 12-16" rip as close to one edge of the rip as possible. It's still the factory edge on the interior of the sled that matters. Let it dry overnight. Now, you can push the sole of your saws sled (keeping the widest part of the sled against your 4" factory edge) and run the saw down the entire luan sled. That will cut off a portion of the luan sled. THAT cutoff line is your mark for all cuts to come. If you line that edge up against your mark, the blade will cut exactly there, as long as you keep the saw's sole plate firmly against the factory edge you used to cut that new edge.

Here is an example:

hmm, can't seem to get it to see the pic here so let me post a link to the pic and see if that works for anyone....

http://www.flickr.com/photos/[email protected]/8303311158/

Heck, even better, here is the video that inspired me to make mine

http://www.youtube.com/watch?feature=player_embedded&v=CH5dW-QcgeI

Paul


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## bradnailer (Nov 11, 2008)

mobilepaul said:


> Late to the party, here, but I would make a sled for the circ saw AND get a good blade. HD sells a Diablo for 16-20 bucks that would give you smooth results.
> 
> I went to HD and purchased a sheet of their 1/4" luan and cut a 4" strip off a good 8' edge. It's the edge that matters, not your cut. Then, cut a 12-16" slice 8' long. This cut doesn't really matter either, just try to keep it as straight as possible. Take the 4" rip with the factory edge facing inward and glue it well to the 12-16" rip as close to one edge of the rip as possible. It's still the factory edge on the interior of the sled that matters. Let it dry overnight. Now, you can push the sole of your saws sled (keeping the widest part of the sled against your 4" factory edge) and run the saw down the entire luan sled. That will cut off a portion of the luan sled. THAT cutoff line is your mark for all cuts to come. If you line that edge up against your mark, the blade will cut exactly there, as long as you keep the saw's sole plate firmly against the factory edge you used to cut that new edge.
> 
> ...


Wow, I really like that sheet goods cutting jig. I believe I'll make one. I probably have enough scrap material to build it. 

Once the jig is set up, you could also run down the kerf line with a sharp utility knife to minimize tearout.


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## mobilepaul (Nov 8, 2012)

bradnailer said:


> Wow, I really like that sheet goods cutting jig. I believe I'll make one. I probably have enough scrap material to build it.
> 
> Once the jig is set up, you could also run down the kerf line with a sharp utility knife to minimize tearout.


you're right, it would minimize tearout. I waxed mine a couple of times, too, before I used it. It really works great and you can bust down a good bit of sheet goods in no time.

with one full luan sheet I made an 8 foot one for rips and a 4 foot one for crosscuts. It really helps. I put one of those Diablo blades on and away I went. I had 8 sheets of plywood to bust down into 8 feet long by 6" strips the next day and all I had to do is line up the marks with the edge of the sled and cut. Worked great, with every cut straight and no tearout for me. You do, however, have to be cognizant about which side of the line you need to cut on based upon the way your saw needs to slide along the sled.


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## Brian T. (Dec 19, 2012)

1. I don't read so far that anyone recommends buying a blade specifically made for cutting plywood! Very fine tooth blade.
That reduces the tear out. Works for me.
2. If you can use good-one-side, cut from the back.
3. Looking down on your saw, if the blade is on the right, run a guide along the left side.
4. Start a fake cut in scrap. Shut the saw off and put it back in the slot. Look very, very carefully to decide if the little mark on the saw shoe matches the left side of the saw blade kerf. I did all that then used a 3-corner file to make a bright little nick in the saw shoe
which has made a world of difference in free-hand accuracy to follow a line.


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## jschaben (Apr 1, 2010)

A little different approach. Storing 8ft+ jigs is a little problematic for me so I went this way. Does depend on a good factory edge but does give a zero cleance at the kerf.:smile:


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## mobilepaul (Nov 8, 2012)

jschaben said:


> A little different approach. Storing 8ft+ jigs is a little problematic for me so I went this way. Does depend on a good factory edge but does give a zero cleance at the kerf.:smile:


That's actually a nice rig as well, jschaben... I can see where that could come in handy. As far as storage, for me, I just lay my two sleds on top of whatever wood is on my storage rack. It really doesn't take up dedicated room that way.


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## mobilepaul (Nov 8, 2012)

Robson Valley said:


> 1. I don't read so far that anyone recommends buying a blade specifically made for cutting plywood! Very fine tooth blade.
> That reduces the tear out. Works for me.
> 2. If you can use good-one-side, cut from the back.
> 3. Looking down on your saw, if the blade is on the right, run a guide along the left side.
> ...



I agree with you Robson, a plywood blade is a good thing, sometimes. I always have one around. Some people are good with cutting freehand and some aren't. If I had just one sheet, I would not have made the sleds, but, now that I have them, they will be utilized over and over again. I had to make 8 8' rips in each sheet and I had 8 sheets. It just seems easier, to me, to have this sled, make a mark at each end, and cut away. They are all uniform, as long as you measure correctly, and you can just go and go. Just my way of doing things, not for everyone...


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