Cutting plywood beyond capacity of the table saw – safely
All,
As many know, I am working out the details and even going over how the cuts should look as they are being cut and preparing what to expect, etc.
While I am waiting for my plywood supplier to get some stock in, I have a question or two. I am thinking of using a circular saw to rough cut the plywood onto manageable sizes before final dimensioning the sizes that are within the saw’s capacity.
1. Do you use the factory edge as is? My thinking is to cut it off since it probably is not clean even on A-1 ply. Should I just get a straight edge and a circular saw to trim the edge off? Should I run the this waste cut along the fence? From my understanding, usually the good piece goes against the fence except I do not have the capacity to do that.
Now for final dimensioning :
2. my jobsite saw has 32.5″ right, 22″ left rip capacity. If I want to make a 36″ cut, would I just hope to make good cuts with the circular saw and straight edge? Would it be wise to cut the excess off by putting the waste side against the fence (taking the kerf into consideration so the non-fence side is the desired dimensions)?
3. Can I clamp the ply into a larger crosscut sled with sufficient depth (front to back) for the sheet and just support the length hanging off during the cut? the ply will be at most 36 ” x 24″ and I believe I can easily make a sled to handle that capacity. I 36″ x36″ sled center cut would support roughly 18″ of the 36″. I would need a side stand to support the hangover. I am already planning infeed and outfeed extensions so the sled should be fully supported and a left side extension that will also double as a router table. The sled will have channels for bolts to pass through (alla Stumpy Nubs large table) or T track for a clamp on either side of the blade to hold any wood down on the base. Sure, this is moving the wood instead of the saw but I think it will result in cleaner edges that is easier to repeat and be square.
4. Alternatives?
What is the safest way besides downsizing my cabinets so that the Top, back bottom and front only need 32.5″. That is my ace in the hole. Should I muck up cutting 36, I can always downsize the four panels and just live with a narrower cabinet.
Thanks in advance.
Frank
Replies
A track saw is the best tool for the job. With a good one, you'll get perfect edges right off the saw.
Choice number 2 is cutting oversize with a circular saw, and make final cuts on the table saw. I use the factory edge against the fence, cutting a little over. Then run your just cut edge against the fence, and cut the factory edge off to your final size.
I most often make crosscut against the fence too, when possible. If you have 3 shelves, for instance, cut the length first, then rip the 3 shelves. Just don't try to cut small or narrow pieces using just the fence. Use the miter gauge or sled for that.
came here to say that and john beat me to it. i break down all plywood with a cut table, a sheet of rigid foam insulation and a track saw (festool).
i lay the sheet of insulation on my cut table, plywood sheet on top of it and set the cut depth just to clear the plywood and score the insulation. fast, easy and very safe.
I agree the track saw is the best option and what I use but I didn't get the impression, since he was asking the question, that he owned one. Given that for about $50 he can construct the saw guides I describe below and accomplish close to the same thing with a little care it may be the better option for him. There are also less expensive saw guides available commercially for much less than a track saw as well that perform adequately. Bora and Kreg are 2 manufacturers I know of that offer acceptable systems for less than $200
The one thing I hate to see is hobbyist trying to wrestle large sheets of plywood though a small light weight jobsite saw with a bunch of cobbled together supports. What I can do using my 400lb Unisaw with its 52" rails and extension table and solid outfeed table is another thing. It is important to tailor your processes to the tools you own.
A lot of questions to answer.
First never rely on the factory edge it will be rough nicked up and potentially out of square.
2. Have your local big box store rip a 8"x 96" piece of their thinnest hardboard then cut another 8-10" piece from the end of the remaining piece. Attach to these a STRAIGHT piece of stock about 2" wide along one of the long edges. These do not need to be absolutely parallel because you will rip it to the perfect width for your circular saw before you use it.
While you are at the Home Center pick up a 4 x 8 piece of high density foam board. Set this up on a stable platform on top of a sheet of plywood or MDF. You can lay the foam board on the floor but it will make it difficult to clamp the cutting guides you made above so I recommend some type of platform. Set the saw blade to cut 1/4" more than the thickness of the hardboard then Take the guides you made and lay them on the foam board and holding your saw tight to the fence rip them the entire length of both guides. This will give you a guide perfectly fitted to your saw. So where you place the edge of the guide is where the saw will cut.
Now rip 2 more pieces of the hardboard about 2" wide and at least 38" long. Take another piece of straight stock at least 6" Long and make 2 T-squares exactly 36"from the fence. Use these to position your guide by holding them tight to a good edge of the plywood, you can clamp them in place, then slide the edge of the guide up to the end of the t-squares and clamp it in place. Doing this is much more accurate than trying to measure exactly 36" every time. Keep in mind the board will be short of 36" by the width of your kerf unless you account for that when you make the t-squares by making them a bit longer. By cutting on top of the foam board you will support the cut better reducing tearout and not having to worry about what is under your blade. Use the short guide to make your crosscuts, it will be safer and easier than trying to muscle long pieces through a sled on a smaller saw. Just measure carefully and use a good square to align the guide edge.
I know that is probably as clear as mud but it's hard to give detailed instructions in this forum especially on a phone.
Per John_C2's option #2, with better grades of plywood I find the factory edges straight enough for use as he describes, but in lower grades there can be enough wrong with them that I don't use them.
A different method I have used: with most T-square style fences, the table is actually a decent amount wider than the rip capacity of the saw (because of the width of the T portion). If my desired width is only a few inches greater than the capacity of my saw, I will use a very straight parallel-sided piece of stock as a fence, and I place it by referencing it off the outside of the rip fence and clamping it to the table. When you remove the rip fence, you have the capability to rip somewhat wider than the stated capacity of your saw. This method also allows you to make the temporary fence as long as you wish, so it can add some stability to your cut.
If this method works for you, you can even make a spacer so that you can place the temporary fence using the scale on the factory fence--for example, the space might be sized so that your actual cut dimension would be 10" greater than what you read on the scale.
Not sure if it will work with a jobsite saw--for one thing, if the table is cast metal it may be tricky to clamp stuff to it even if you have the width.
If you do end up using the table saw for this, make sure to have good infeed & outfeed support. Not sure if you have much danger of kickback with pieces this big, but you can definitely destroy your stock if you lose control. With the cost of even utility-grade materials right now, you certainly don't want to risk wasting anything if you can help it.
Alternatives: I don't use plywood much but I have used a certain orange themed big-box store with success. Since they have a vertical track saw in their lumber department, I pull the sheet out and acurately mark the cut points with tape with the waste side clearly evident. Then the barely qualified employee and I load the board on the rails and I double-check the blade alignment.
Got all the cuts done to tolerance and never had to wrestle the whole sheet. I don't own my own track saw and work in a small shop, so being able to bring home accurately pre-cut panels has really smoothed things out for me.
You are very lucky. I would never trust either the employees or the saws to give me a usable edge, especially crosscutting plywood the blades they used are just too coarse designed for quick cuts not good ones.
I sometimes have them break sheets down, to make wrestling the plywood home easier. But the cuts ALWAYS splinter badly. The edges come out straight enough to use against a tablesaw fence, but never, ever as a finished edge.
I think they last put a sharp blade on those saws during the Carter administration.
If the panel of ply is 24" tall and I want to cut it down to 36" wide, is there any reason this cannot or shouldn't be done in a crosscut sled?
I was always told that a miter or sled is for things wider than tall.
Is the limit for using the crosscut sled the dimensions, front to back, of the sled (as in what fit in it)? Can you cut things in a sled longer than the width of the sled? Of course with support.
Thanks for helping this newbie out.
I think the dimensions you provided are incorrect. In almost 50 years of making sawdust I have yet been able to figure out how to cut something 24" down to 36". ;-)
As for the limits of a crosscut sled, well it depends. The size of sled that I can safely use on my saw which is a professional cabinet saw and weighs hundreds of pounds and is firmly anchored to the ground will be different than your small jobsite saw which probably weighs less than 75lbs. Mass has its advantages when you are trying to push large heavy sheet goods through them.
The other limiting factor is jobsite saws often have very little table in front of the blades making it difficult to keep a large crosscut sled balanced and stable at the beginning of the cut it will be compounded if the piece is long and hanging off the edge of the sled several feet.
Another factor is also the length of your arms. My largest sled is 27" internal which permits me to cut 24" wide panels at 6' 2" that combination is getting close to my limit. This can be extended a bit if your sled design incorporates some type of clamping system but when I cut 24" wide panels it barely let's me use my clamps in a 27" sled.
I personally would not try to cut large panels on a jobsite saw using a sled it will be trickier than you think. There is a reason pros like myself have mostly switched to using tracksaws to breakdown sheet goods.
If you read my earlier post there is an easy method to fashion a portable saw guide and to use that to safely and more accurately make the cuts you need to make. If it was me I would find some system that let's me move the saw through the workpiece rather than a large workpiece through a jobsite saw.
The piece of ply I was referring to was 24” high by over 36” wide. I was not suggesting cutting a too small panel bigger.
I was thinking of cutting the ply down in 24” pieces and then use the sled to cut the width to 36” from some wider width. Not sure it would be a full 48” but would be at least rough cut and final cut to 36” wide.
I already have built a guide from some Luan and a piece of hardwood board. I made it at the time only 6ft because the 1/4” luan was maxed at that length. I could use it to cut the panels to 36” wide. I just never liked the cuts with it. I was just curious if I could use it for rough cuts to say 38” and finalize with the sled to 36”
As for the jobsite, I am adding in and out feed table extensions to help as well prior to my cabinet work beginning.
It's more a matter of how much wood is bearing against the fence. If you have a piece of ply that is 36" across the grain and only 4 inches with the grain, it would be hazardous to run the 4" side against the fence. A sled or miter gauge would be called for.
But a piece 36" across the grain and 24" with the grain is fine. I would run the 24" side against the fence and make your cut.
esch5995,
Thank you all your guidance. Not sure I understood the ‘clear as mud’ post. Please allow me to indicate what I understand and tell me if I am on track.
In the first paragraph you have me make a 8ft and a ~40” hardboard that are 8” wide and attach a straight hardwood stock (2” wide by the length of the board) to make straight edge guide for a circular saw.
Next you want me to to cut two pieces of the hardboard 2”x 38” or longer and make two T squares that are 36” from the hardwood crossing ‘T’ and use that to butt up the cut side of the guide made previously.
I do not know the kerf of my saw but assuming it is 1/8”( which I am sure it is not but the math is easier), should I make the T square 38 and 1/8” so I will result in a 36” piece?
This is like a poor man’s TPG parallel guide system for a track saw
Am I close to your suggestion?
You pretty much nailed it. The key measurement is to make the guide wider than the wide portion of you saws base plate to the inside of the blade plus the width of the "fence" 2" is an arbitrary number if you have an 1 1/2" x 8' piece of straight stock use it. The reason you want it a little wider is so that you can trim it to an exact fit later the 8" figure could be more than you need.
I wood have the Home Center make all these cuts and the 2" wide strips for the t-squares as well.
The reason for the t-squares is to eliminate as much measuring as possible. Measuring introduces errors that's why we use fences and stop blocks to insure repeatability. The guides will tell you exactly where you will be cutting but trying to line up on pencil lines will still result in discrepancies, hence the t-squares.
The one advantage that a tracksaw has that this type of guide doesn't is it locks the saw in all planes. This type of guide can still let the saw drift away from the fence if you get careless so be sure to keep pressure against the fence. I recommend a trial run with the blade raised to make sure you can maintain a smooth comfortable pace with pressure against the fence the entire length of the cut before actually cutting the material. With this guide you don't need to actually see the cut so having the guide between you and the saw could be the best plan that should provide natural pressure against the fence. If it is a corded saw make sure it won't snag, I usually toss it over my shoulder.
If you have any other questions I keep checking back.
https://www.finewoodworking.com/2005/10/25/cutting-sheet-goods-with-a-circular-saw
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