Accurate 90° cut on plywood - how?

[Mark Gibney]

How can I make an accurate, repeatable 90° cut on plywood that is too wide for my table saw sled?

I don't have a sliding table saw, I do have a Festool track saw. But not their MFT table.

When I google to find a jig it keeps taking me to Pinterest pages, which I am not a member of, and are of no use to me. Highly aggravating.

If this question has been answered on a previous thread I'd appreciate being pointed in that direction.

Thank you, Mark

[JAY FOSTER]

Just use your Festool track saw, you don't need their MFT table. Set the depth of cut accordingly and place some scrap wood underneath the plywood and cut it on the floor or workbench. I have seen some people but a large 4x8 sheet of foamboard (insulation) to place under the plywood as a sacrificial piece.
1:05 https://www.youtube.com/watch?v=BSF9fKgwGpc
https://www.youtube.com/watch?v=SE8Cjfb7VY8

[David Bassett]

How can I make an accurate, repeatable 90° cut on plywood that is too wide for my table saw sled?

I don't have a sliding table saw, I do have a Festool track saw. But not their MFT table.

When I google to find a jig it keeps taking me to Pinterest pages, which I am not a member of, and are of no use to me. Highly aggravating.

If this question has been answered on a previous thread I'd appreciate being pointed in that direction.

Thank you, Mark

To search this site, add "site:sawmillcreek.org" (without quotes) to the search terms with Google (and probably other search engines.)

As far as a quick answer, I'd say with your track saw and *VERY* careful layout.

[George Bokros]

If you square the track saw track to the edge you should get a 90* cut, you do not need a MFT to do so. I have a Eureka Zone track saw and use a support on saw horses and make 90* cuts on ply all the time. I do use the clamps to secure the track to the ply so it does not slip while cutting though.

[Jim Becker]

Just measure carefully and the track saw will do the job accurately and safely

[Jim Morgan]

If you square the track saw track to the edge you should get a 90* cut, you do not need a MFT to do so. I have a Eureka Zone track saw and use a support on saw horses and make 90* cuts on ply all the time. I do use the clamps to secure the track to the ply so it does not slip while cutting though.

+1 on the EZ track. I use a framing square to line it up before clamping & check afterwards. I have a Woodpecker, but any framing square tuned to 90 degrees works. Of course, this is not for high-volume workflow. If that's what you need, you might look into a panel saw.

[JAY FOSTER]

Yes, I forgot to use a square, either a large speed square - https://www.amazon.com/Swanson-Tool-T0701-Speedlite-Structural/dp/B0008JF0TE/ref=sr_1_4?s=hi&ie=UTF8&qid=1516582377&sr=1-4&keywords=Speedlite+Square+Layout+Tool, or even a large drywall square - https://www.homedepot.com/p/Empire-48-in-Drywall-T-Square-410-48/202035306

[David Bassett]

Yes, I forgot to use a square, either a large speed square - https://www.amazon.com/Swanson-Tool-T0701-Speedlite-Structural/dp/B0008JF0TE/ref=sr_1_4?s=hi&ie=UTF8&qid=1516582377&sr=1-4&keywords=Speedlite+Square+Layout+Tool, or even a large drywall square - https://www.homedepot.com/p/Empire-48-in-Drywall-T-Square-410-48/202035306

Or, (especially if this is a one-off deal,) go a little slower and just measure the diagonals, corner to corner, of your layout lines.

[Bryan Lisowski]

One thing to add is to do a squaring cut with your track saw. Plywood isn't always square from the factory, so you may need to take off an 1/8" from the factory edge and then do your cuts.

[Lee Schierer]

Factory edges and ends of plywood are nearly perfectly straight and at 90 degrees to each other. Use a second full or partial sheet of plywood aligned with the edges of the piece to be cut to align your track saw fence at 90 degree so the blade will cut the sheet underneath at the correct location.

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[Alan Lightstone]

I use a large triangle and my Festool track saw. Works just fine.

[Simon MacGowen]

How can I make an accurate, repeatable 90° cut on plywood that is too wide for my table saw sled?

I don't have a sliding table saw, I do have a Festool track saw. But not their MFT table.

When I google to find a jig it keeps taking me to Pinterest pages, which I am not a member of, and are of no use to me. Highly aggravating.

If this question has been answered on a previous thread I'd appreciate being pointed in that direction.

Thank you, Mark

Are you willing to invest in order to achieve your goal?

If not, skip the next link:

https://www.youtube.com/watch?v=AmNyPvsfSCo

No other squares can match this jig and no other ordinary methods are as quick as it to get the same result.

I am not related to this company but my club fellows highly recommend it.

Simon

[Malcolm McLeod]

How can I make an accurate, repeatable 90° cut on plywood that is too wide for my table saw sled?

I don't have a sliding table saw, I do have a Festool track saw. But not their MFT table.

When I google to find a jig it keeps taking me to Pinterest pages, which I am not a member of, and are of no use to me. Highly aggravating.

If this question has been answered on a previous thread I'd appreciate being pointed in that direction.

Thank you, Mark

Since you have the track saw, the cutting aspect of this seems to be covered (as others have stated). If you're worried about layout and getting the angle just right, use the 3-4-5 rule:
Off of a corner, accurately measure 4' across and mark the base line. Measure up from that corner 3', and at the same time measure the hypotenuse at 5' (from your mark to the 3' vertical). Result is perfect 90deg corner. If 'feet' is too big, use any common convenient multiple; i.e. 4" , so 3 x 4"= 12" hgt, 4 x 4" = 16" base, & 5 x 4" = 20" hyp.

I'm sure you can web search for 3-4-5 triangle and/or Pythagoras' Theorem.

[Jacques Gagnon]

+1

Some form of trammel (or story stick) can be used instead of a steel tape; the principle remains the same: 3-4-5. This is the triangle that Alan refers to (#11).

[Mark Gibney]

Thank you all for your feedback. I use the 345 layout all the time, but I want something faster for when I need to make a lot of cabinet boxes.

Simon - that TSO aftermarket jig in the video is exactly what I could use. Have you used it? Is it accurate?

Another route is go is to get a cheap panel saw like what Rockler or Milwaukee sell, but these tend to have a bad rap unless you go to the high end expensive units. However, if it's set up square and used just for cross cuts it might remain square.

There's a fairly rough looking one locally on craigslist for $325. Any opinions?

https://losangeles.craigslist.org/wst/tls/d/plywood-and-panel-saw/6456361930.html

[Simon MacGowen]

Thank you all for your feedback. I use the 345 layout all the time, but I want something faster for when I need to make a lot of cabinet boxes.

Simon - that TSO aftermarket jig in the video is exactly what I could use. Have you used it? Is it accurate?

Another route is go is to get a cheap panel saw like what Rockler or Milwaukee sell, but these tend to have a bad rap unless you go to the high end expensive units. However, if it's set up square and used just for cross cuts it might remain square.

There's a fairly rough looking one locally on craigslist for $325. Any opinions?

https://losangeles.craigslist.org/wst/tls/d/plywood-and-panel-saw/6456361930.html

Never used the TSO jig myself but some of my club guys are full-time cabinetmakers in one-man shop environment and I have no reasons not to believe their words given their stellar track records when it comes to tool recommendations. Some have the Festool set (plunge saw + MFT set up) but still use the TSO jig and that speaks for itself.

I seldom use large plywood stock and when I do, I don't need the degree of accuracy that is demonstrated in the video.

Simon

[Art Mann]

You are making this too complicated. If you have a track saw, you already have the only tool required with the exception of a couple of sawhorses with sacrificial 2X4s stretched across them. Use geometry or use a framing square. It is easier than you think.

[Ted Derryberry]

I have to disagree that plywood is typically straight and square. In my experience, primarily with 4x8 baltic birch for the last 8 years, it is usually not straight and square. In fact, I bought a track saw just to straighten an edge so I could get an accurate 90 degree cut on my panel saw. Finally got a slider last month and life's much easier.

[Simon MacGowen]

I have to disagree that plywood is typically straight and square. In my experience, primarily with 4x8 baltic birch for the last 8 years, is usually not straight and square. In fact, I bought a track saw just to straighten an edge so I could get an accurate 90 degree cut on my panel saw. Finally got a slider last month and life's much easier.

Agreed.

Those panel saws at Home Depot and Lowe's are subject to abuse and become rough cut tools and precision is not a concern. I have seen dirt or saw dust on the tracks where they rest the panels on. It is also a big question if anyone there ever maintains or knows how to maintain those saws even if they were able to make square cuts at the beginning.

Simon

[Ted Derryberry]

Well, my panel saw is maintained much better than anything at a big box store, but when you're starting with plywood that doesn't have a straight edge it doesn't matter. You will get a cut that's 90 degrees to something, but that could be one end of the plywood, or the other, or tangent to a curve.

Obviously some plywood might be straight and square, but here's a few things I've seen. Baltic birch with and 1/8" "dive" in the last 2' of a 4x8 sheet, both sides being parallel. I got about 6 or 8 sheets like this in one bundle. Sandeply from Home Depot that was out of square on one or both ends, sometimes the sides weren't even the same length. MDF, from a hardwood/plywood supplier, not a big box store, that is out of square by about 1/8" on the diagonals. I've been doing this long enough that I work on the assumption that sheet goods are not straight or square and life's a lot easier than getting to assembly and finding everything is a rhombus because I trusted the material.

[Mark Gibney]

For sure plywood is hardly ever square, and I just presume it isn't.
I use the track saw and the table saw to make rip cuts, but I want to make cross cuts fast accurate and repeatable. I'm leaning towards getting the TSO jig that attaches to the track, but I'd still like to hear what people would think on that cheap n cheerful panel saw on craigslist that I posted the link to above.

Properly maintained and used only for cross cuts - would it be accurate, or at the low end of the market are they a fool's errand?

here's the link again

https://losangeles.craigslist.org/wst/tls/d/plywood-and-panel-saw/6456361930.html

[Simon MacGowen]

Properly maintained and used only for cross cuts - would it be accurate, or at the low end of the market are they a fool's errand?

here's the link again

https://losangeles.craigslist.org/wst/tls/d/plywood-and-panel-saw/6456361930.html

Never used a panel saw before and I always assume those at the big box stores used (abused?) daily are rough cut tools. It is hard to tell how good the saw in the ad is and how difficult it is to reset it to cut true and square.

Between the TSO GRS16 (or GRS 16PE) and the panel saw seen in the ad, if I were you, I'd choose the TSO jig because
I would already have the Festool saw and track, I don't want another bulky shop tool (that I might not use too often), dust collection is great with the Festool approach, there is no maintenance required, and the GRS16 would cost less money. I am assuming here both tools cut square.

Again, no ties to TSO whatsoever...and I don't have its jig.

Simon

[Ted Derryberry]

If I already had all the festool stuff (I don't) I'd get the TSO jig over the panel saw, and I'm a relatively happy owner of a panel saw. About all I ever used mine for was to establish a square corner to work from on the table saw. I'd spend one day a week cutting up six sheets of plywood and make maybe 12 cuts on the panel saw. The time saving vs. the TSO jig doesn't offset the cost and space requirements of the panel saw.

Not knocking panel saws, they are very handy and quick. I thought I'd sell mine once I got the slider in the shop, but after almost a month I've decided to keep the panel saw because it's just so handy for certain things in my workflow. I don't have the room to leave the crosscut fence mounted to the slider all the time.

[lowell holmes]

Hey guys,
A straight 1x4, 2 clamps,and a skilsaw is all you need. That's how we did it 20 years ago.

[George Bokros]

I always make a cross cut on ply using the long edge as the base. The long edges are usually parallel it is just the cross, the 48" edge that is not square to the long side. The 48" side is subject to the cutting process but the long edges are usually parallel at least in my findings.

[Ted Derryberry]

They can be parallel, but not straight, in which case there's nothing to reference the 90 degree cut off of.

[Patrick Whitehorn]

Maybe I am confused, but did that video demonstrate a 4-cut version of the 5-cut method? (I am not saying that the jig is bad, just that I don't understand why we should trust the measurements taken/shown.)

Patrick

[Pat Barry]

If I were needing to do this a lot, I would use the tracksaw method but I would want to have the track connected to a square (90 deg) edge of sufficient span so that I could mark and register the track from the starting edge and trust that the track is square. Nothing more of a pain in the butt than to have to measure both sides, try and line up the track at both ends, then clamp it, check it, etc. I don't have a Festool but I'd be surprised they haven't a solution for this.

[mike sato]

How about building a square like this to line up your track saw:

377373
Click to view large image.

Could build different size squares to suit your needs. Just use the 3,4,5 rule.
Real cheap.....:).

[glenn bradley]

I add -site:www.pinterest.com to my searches. Pinterest is a cancer on the internet.

[George Bokros]

They can be parallel, but not straight, in which case there's nothing to reference the 90 degree cut off of.

If the long edges are parallel and you are squaring the end to an edge do you not end up with a square cut panel?

[Dave Zellers]

Maybe I am confused, but did that video demonstrate a 4-cut version of the 5-cut method? (I am not saying that the jig is bad, just that I don't understand why we should trust the measurements taken/shown.)

Patrick
The first cut on the 5 cut method is only there to be sure you are working from a straight edge. If you know the starting edge is straight, you only need 4 cuts.