Making wide, square/perpendicular crosscuts

[Jon Endres]

I saw the very recent thread on assembling cabinet boxes, but I decided that this question necessitated its' own post. I have built cabinets before, my kitchen and several bath vanities, and due to face frame construction, modular design and attached backs, have never had issues keeping the boxes square enough. However, I seem to be having a problem lately with getting the actual parts square, i.e. having two edges perpendicular to each other. I don't really have the capability to crosscut an 8' long, 24" wide sheet of plywood with my table saw, so I make the cuts by marking with a reasonably accurate framing square or a good quality drywall t-square and then crosscutting with my track saw (an older EZ-Smart setup). I am finding that my parts are out of square. By out of square, when I measure diagonals, they could be as much as 1/8" difference between the diagonals, which is way too much for me. I would be happy with 1/32" or even 1mm (I can metric too!) which would get me a decently square enough cabinet piece. It's either my measuring technique, the square itself which is inaccurate, or my cutting method, but I find if I am careful, I can split a line made by a 0.5mm mechanical pencil with my cuts. So I'm pretty sure it's the square.

What techniques do you guys use, those of you who don't have a $8,000 sliding panel saw in your shop, to guarantee that your cabinet parts, or ANY large wide crosscut, is square to an adjacent edge? What tools would be recommended to mark a highly accurate perpendicular cut line? The YouTube videos I've seen on cabinet construction kind of gloss over the whole thing, they go from full sheets to a pile of cut parts in high-speed or stop-motion and nobody even mentions measuring and marking.

[Marc Fenneuff]

I suffered this way with cabinet carcasses for a couple years, relying on the factory corner to be my perpendicular (and was always disappointed). Simplest way to get accuracy in your case is to cut the long side on your TS with the rip fence, and cut the short side with a simple single-runner crosscut sled. If you square the fence on your crosscut sled adequately you'll get a satisfactory 90 for your carcass parts. Break down your 4x8 sheets as necessary first with a track saw or circ saw and straightedge.

[Maurice Mcmurry]

I made that type of cut with the Skilsaw and homemade guide rails for years. It is not easy to get them prefect. A few years ago I bought a small vertical panel saw for $1200.00. I have modified it with a full length rail and it does a very good job.

[ChrisA Edwards]

I had similar issues doing similar length crosscuts on large panels.

I already had a Festool track saw, Festool MFT (which for me has been a bit of a white elephant), but by themselves, did not give me the crosscut capability I was after.

So I bought the Part II Bench Dog jig ($200), a 4'x8' sheet of MDF and made myself a portable MFT style top.

With bench dogs, my new portable top and my old Festool track saw and 55" track, I can now crosscut 3 feet.

[Jack Frederick]

I recently built my own MFT (42x76) using the Parf Guide Mark II. I’ve added the various dogs from UJK and using my Festool track saw have been very pleased with the results. I’m doing dadoes and rabbits on the track rail as well with the Festool 1400 router and the micro adjust track attachment. I’m still checking every cut on this thing as it is still fairly new to me, but everything is coming up square. I can accurately cut a 48’ piece of plywood. I guess going lengthwise I could handle the long rip as well but have not done so yet. I’m working out a system for stops for cutting identical lengths. I’ve owned the TS55 for years and always liked it for sheet goods but that was only occasional use. Now, I use it all the time. Rather than taking the big material to the saw I am now taking the saw to the big material. Better for me.

[Kevin Jenness]

I used a sled on the tablesaw for many years with consistent, acceptable results. A tracksaw setup as described above should work as well.

If you doubt your square, its easy enough to check it. Cut a straight edge on a panel as wide as your square will reach, scribe a line "square" to the edge with the blade, flip the square over and compare to the scribed line. Framing squares can be trued up by peening the corner.

[Jon Endres]

How accurate do you think a vintage drafting t-square would be? Ex. Dietzgen, Keuffel & Esser? I have a few of them floating around but have never considered using them in the wood shop, always thought they were too fragile. Used them for decades to actually draw, obviously trusted them for paper drawings so they should be reliable for shop use?

EDIT: I know a lot of you enjoy your Festool stuff but I nearly went broke buying a Domino, so that's not likely to happen. I am leaning more towards a Woodpeckers 2616 Precision Square. Might be able to swing that cost but holy crap that's a lot of coin for a chunk of aluminum.

[Kevin Jenness]

Just get a framing square, file the edges straight if need be, and peen it into square if needed as described above. A large drafting square with a wooden tongue can be trued up with a rabbet plane. You can make a large square of wood or sheet material. The important thing is to have a long, straight tongue and blade, a straight edge on your workpiece, to check that your square is really square and adjust it if not. You can't necessarily rely on a brand name.

[Jamie Buxton]

I made myself a big speedsquare. By big I mean the arms are 52” long. I tested and tuned this tool until it now is the most accurate 90 degrees in my shop. (Did you know that the 1/32” error you want in a 48” crosscut is .03 degrees?!)

Testing a big square isn’t difficult. First cut a straight edge on the 96” edge of some sheet good. MDF is cheap. You do need a straight edge, accurate to whatever precision you want on your square. Use your square to crosscut the sheet in the middle. Fold the two halves together like you’re closing a book. The two parts of the 96” edge will align, and the two crosscut edges will align. If the 90 degree angle is not 90 you can see how much to tune the square. It may take several iterations to get it right.

How you tune the square depends upon how you built it. I tuned mine by hand planing the edge of the crosscut arm. However if I were to do it again I’d make the square like a drywall square, so tuning could be done by loosening a screw at one end of the diagonal brace. When I got 90 degrees I’d add more screws so there’s no chance of slippage.

[David Stone (CT)]

I don't really have the capability to crosscut an 8' long, 24" wide sheet of plywood with my table saw, so I make the cuts by marking with a reasonably accurate framing square or a good quality drywall t-square and then crosscutting with my track saw (an older EZ-Smart setup).

I would reverse the order: use the tracksaw to crosscut the 8' long 24 inch wide section of plywood into shorter sections/rough cut parts that are no longer too unwieldy to cut safely and accurately on the table saw, then use the table saw with a sled capable of handling 24 inch wide stock to cut that stock to final panel sizes. This set-up should produce panels that are plenty square enough--I built a kitchen this way using a very modest table saw.

[lowell holmes]

A straight1X4 and skill saw make a fair track saw. Just clamp the straight edge to the plywood and use it as a straight edge. Practice before making serious cuts.

[Michael Schuch]

You didn't mention if you have a track saw or not? I love my track saw and it makes those cuts go MUCH easier. My 16" radial arm keeps a good 90 degree cutting angle but it doesn't have a 24" cut. Before my track saw I would cut 2/3rds of the way through a 24" wide board, flip the board over then finish the cut. With a clean blade notch in the RAS fence alignment was easy and I got very good very close to square cuts.

Like it was mentioned above DO NOT ASSUME THE FACTORY EDGE IS 90 degrees! The problem could very well be at the mill and not with your technique.

[Jack Frederick]

“Loving the Festool stuff…” Classic love/hate. I do love the 55 and only recently got the 1400 for Xmas. I can’t afford the Domino

[Michael Fink]

Glad I'm not the only one fighting this battle. Working on a set of cabinets that's almost 90in high X 20in deep. Did a lot of staring at it wondering how to make an accurate/clean crosscuts on the 96X20 sheets I had after ripping them on the table saw.

I finally threw up my hands and spent some money. I do enough of these big cabinets (as a hobby, not a profession) that I felt it warranted to spend some money (more tools, more better, right?). I got the TPG Parallel guide system for my Makita track saw, and that does appear to be the answer for my needs. It's absolutely dead on accurate/solid (assuming, of course, that you set it up right!). It also killed two birds for me, after cutting the 90x20 sections of plywood, I then needed to dado them to take shelves. Running that through my table saw sounded "not fun" but with the track and parallel guides, I can just run my router along the track using a guide. Nice and easy, and, because of the TPG system, also, perfectly parallel cuts (I ganged the two sides and routed in one go).

The other option that I've looked at and considered over and over, but simply cannot justify, is a radial arm saw. The Original Saw company; looks like a beautiful piece of equipment, 24in cross cut AND dado blade capacity would work for just about any use I have where I need an accurate cross cut or dado placement. But ~6K delivered, plus the space required? And getting rid of my miter saw/miter saw station would hurt too (no need for both of them).

[Robert Engel]

I would abandon the idea of finding the perfect square, and think about an indexed dog setup like the others showed. IMO you can’t beat an MFT type set up for accuracy. You don’t need an expensive tracksaw it will work with what you’ve got. The big issue is drilling the holes. The better jigs are not cheap.

Personally, I don’t worry about it, like David ^ I use a tracksaw to rough cut everything 1/4” oversized, and use a panel sled on the table saw to square/final dimension. I can cut up to 30” wide. But, for panels longer than 50” it get a bit dicey. There, I use a fence set as square as I can get it, and use a router to dial in the edge.

Bottom line, trying to cut square to a line & relying on your eyes is going to lead to frustration, at least for cabinetmaking. I used to use a drywall square that I tweaked by drilling out 3 or the 4 rivets and dialing it in/refasten. But one drop on the floor negated that idea. A triangle square with a cleat to register like Jamie ^ suggested is better.