You're expecting too much from a guide rail and attached square. When people gush about getting perfectly square cuts with that pair of tools you should take it with a grain of salt.

The five cut method is intended to help you make precise adjustments to things that have adjustable parts, like a miter saw or the MFT.

Guide rails are simply extruded and are pretty straight but not true straight edges. Moving the GRS to different places on the guide rail could result in slightly different results. Maybe you could shim the pair to get better results on the "long rail" but likely not on the short one (no shim thin enough?). If you post the lengths of the cuts the thickness of the shim needed can be calculated.

You said the saw is "calibrated" but maybe you didn't adjust the toe? It's possible for imperfect toe adjustment to skew the blade resulting in cuts that aren't perfectly straight but that also causes scoring and in the worst case burning but since you don't mention a problem there...

To be fair, track saws, as someone pointed out elsewhere recently in this forum (and probably many before he too), are not a precision tool because a big part of each cut depends on the user holding the saw. Humanly impossible is for someone to have the same posture or apply the same pressure when using the track saw exactly the same every time. Most of the cabinet work (sheet stock) can be done within the tolerance of a track saw though, and to many, that's good enough for the intended purpose of a track saw.

I agree with Michael Kellough,

I have a selection of Festool tracks, and some of them definitely don't cut square when using the TSO GRS square. It's essentially luck of the draw as to which ones cut square, and which ones don't. It's nothing to do with the TSO square, rather some of the tracks have a very slight curve to them.

Only way to get a guide rail to cut "dead straight" would be to extrude it, then mill the reference surfaces. It can absolutely be done, but I suspect it would push the cost of the rails outside what the market would support.

Last Winter I spent some time auditing my Festool tracks. The tracks that cut square with the TSO square are kept "as-is", the tracks that didn't cut square are marked with a Sharpie and set aside for cutting down into shorter sections for random needs.

Probably not a very satisfying answer, but I think it's important to moderate expectations about what to expect from these systems.....

Hi Tom, appreciate your feedback! This is a good tip that I might use as well. I have several tracks so once I find the most accurate, I might set it aside as a dedicated track. Thanks again for the reassurance on this.

Hi,

  In your chart is the last column the total amount of deviation for one cut over the 140 ish cm length? Or should that last column number be divided by 4  or 5?  Are getting basically .5mm - 1.0mm over roughly 1400mm length? That's pretty good but can be better.

   Some things to consider ................

    You've got one end clamped with out under rail / work piece support. Which is causing lots of bouncing around movement on the far end. Basically you are not using a stabile set up.

    I suggest you try again with the following changes to your cutting set up.

        Make sure the work piece is completely supported by the foam, not hanging off the edge.

        Don't clamp one end. Clamp both ends or not at all. Clamping one end is anchoring just that end. Any weight shifting
   or movement will only move the free end.

      When you start the cut hold the piece / rail down further out in front to keep it firmly planted on the bench.

      Fully plunge the saw before it enters the wood. This helps keep from applying extra force that could skew the rail.

      I like to support the rail ends with scrap so that the rail is less likely to move or flex.


  Hope this helps. Try some more cuts.

Seth

Wonder if the Mafell tracks are any straighter. I'll be in UK this coming year, contemplating picking up an MT55cc...

Funny this should come up. Just last week, one of the guys in the solid surface department bought a Makita track saw. After having me come down to his area to do the cutting with my TS55, whenever he needed to miter the corner of a top with a directional pattern. With non-directional colors, a simple square butt-joint is fine. Traditionally, they did this with a rough cut and straighten that with a router and straight edge, which adds an extra step.
The TS55, with a proper negative rake TCG blade, can get glue-ready cuts. This Makita, not so much. There was a bit of a belly on each part, resulting in a gap on the ends. It wasn't huge, but not acceptable either. I loaned him one of my Lietz blades. It did do better, and maybe some practice with the whole set-up can make it functional, but it was never an issue with the TS55? This is on cuts up to around 30", but most are in the 18"-20" range, with solid surface. I've done seams in HPL well over 60", straight off the saw, but that is more forgiving.
As far as rail squares, I don't use one for square cuts. There are several better ways in a big cabinet shop, including my cross-cut bench. I use a Woodpecker adjustable square to cut angles.

Maybe both GRS are are slightly off? Do you have a good machinist square to check?
These things are produced in batches so if both of your samples are from the same batch they would both be similarly off. It’s unlikely but not impossible the batch is off.

Yeah I have one from a 2019 batch and then I got one from a 2022 to compare and make sure the GRS wasn't the issue. It looks like they're not the issue.

The contact of the GRS to the wood is crucial to the results. You have to make sure the edge of the wood is clean, no dust to throw things off. If that interface is perfect you have to be sure it’s maintained as the clamps is tightened. And you have to do it perfectly all 4 or 5 times.

Seth makes a good point about keeping the rails from shifting. A longer rail has a lot of leverage and the way it can shift most easily is toward minus 90* (as in your results) since the part of the GRS to the left is twice as long as the part under the rail.

It looks like your chart says the length of cut was about 145cm when you started but the stock you used in your video looks more like 14”. Can you clear that up?

I'll have to do more testing and maybe reconsider my setup given what you and Seth mention so that there's absolutely no movement/shifting.

Yeah the 145cm was the total length of all 4 cuts (attached the formula breakdown I used) and the difference in the last cut was divided by that.

Quote from: theugshop on November 19, 2022, 11:14 AM

Greetings!
...

I would second what Crazyraceguy wrote. Especially the blades part.

Further, the TS 55 EQ (aka the original no-slides-on-cams TS55) is in the same category as the Makita mentioned. TS 55 R series and newer have the new sliding cams which are infinitely superior to the "original" TS 55 ones like even new Makitas use. One absolutely *can* get precise cuts with the simpler cams. But major care needs to be taken to tune them for almost every cut/every rail while the newer cams are way more forgiving thanks to there being sufficient elasticity/slack in them able to handle most rail irregularities.

That said, the saw is unlikely to be the main issue of yours here. Check my posts here:
https://www.festoolownersgroup.com/festool-tools-accessories/fs-wa-arrived-way-off-square/msg680948/#msg680948

Ah interesting about the sliding cams. Thanks for the link to your other feedback. I don't have a big enough precision square so I'll rely on 5 cut method and once calibrated in as much as possible I'll leave it as a decided track.