TS75 defies straight cuts. What am I doing wrong?

[Kerfmaster]

I recently got a TS 75 and have encountered a surprising challenge with just getting simple, straight cuts. When I use it on guide rails (with Festool clamps front and back on a straightedge line, or with the FS WA at a square 90*) it consistently deviates by about 1/32-1/16 over just a three foot cut. Wondering if I was just garbage with the track I even ran it along a clamped 26" Woodpeckers square. Same issue.

I can't conceive of how the saw could be the issue and I'm fully prepared for my skill to be the weak link here, but I just can't figure out what I'm doing wrong.

I even opened up the saw and calibrated the bevel (I bought it from Festool Recon and on arrival it was about 89.8* at vertical and 46.5* at 45*). But obviously that shouldn't impact a straight cut and, indeed, after calibrating the miter angles it still can't cut a straight line.

I've watched most all the videos on tracksaw technique and guide rail setup, but if there are obvious resources or tips you can point me to, I'd appreciate it.

Thanks!

 

[Mini Me]

Try a different blade?

 

[mino]

First thing, this may seem stupid, but do make sure the cams are tight so there is no wobble.

Second, put the saw on the rail and flip the "assembly" upside down to check the blade is co-planar with the rail when plunged. This can be calibrated as well if not now.

I would do these basic checks before swaping the blade.

 

[Kerfmaster]

Yeah great thoughts. The cams are tight (except for when I run it along the Woodpeckers square, of course). And the blade is toed in just a bit, as prescribed by Festool. I’ve tried more or less toe-in, and it doesn’t seem to matter.

 

[bobtskutter]

The saw runs along the rail, if the rail is bent or moves you won't get a straight cut.
Is the rail bent?  Draw a pencil line next to the splinter guard, flip the rail around and see if it matches the pencil line.
I've had problems if the material isn't properly supported, i.e. it flexes up or down as you cut.  This makes the material move in relation to the rail, especially if the rail is clamped at both ends.  Is your work piece sat on a flat surface?  Try using an MDF board or foam board on the floor (makes it difficult to use rail clamps).
I've also had non straight cuts if I move the saw too fast.  The TS75 has huge amounts of power and can cut very quickly, but don't go crazy with it.
You may even by tipping the saw over as you push it along.  The saw runs along the two green strips so it can be tipped very slightly if you're not careful.  Make sure you push the saw in line with the rail, not at a slight angle.  I.e. think about "jabbing someone" and not doing a "swing punch".  (probably not very good examples).

Regards
Bob

 

[Michael Kellough]

It may simply be that your test cut is too short.

Make a 6 foot cut and check the 3 feet in the middle where the full blade passed through.
The beginning and end (especially the end) of a cut are often a little off since only part of the blade has been used.
Especially if the toe-in is more than required.

 

[Sparktrician]

Any chance your rail might not be true?  You might put it up against a 6' level, just to check. 

 

[Ebuwan]

with my TS75 i would get weird cuts; a while later, took a straight edge to my 1400 rail, where the cams connect, and low and behold, that junk wasn't straight...

 

[Svar]

Which way does it deviate? Towards or away from the rail?
It looks like blade deflection. Is there any burning or excessive teeth marks on either side?
I set my blade strictly parallel to the rail, ignoring "toe in" recommended by Festool.
Make a scoring cut few mm deep and see what happens.

 

[bobtskutter]

Lots of people talk about toe-in or toe-out for the track saw.  The saw runs along the rib on the guide rail, that's the reference edge.  The toe of the saw blade will change the width of the kerf but it's the rib on the rail that determines if the cut is straight.  So long as it's not a plunge cut into the middle of the work piece.  I can see why an excessive toe angle might cause the rail to deflect on the rubber strips, but if the rail is clamped that shouldn't happen.

Why does the toe angle of the saw make any difference to the cut being straight?

Regards
Bob

 

[Svar]

Why does the toe angle of the saw make any difference to the cut being straight?

The blade if flexible. If toe in/out is extreme the blade may progressively deflect in or out as the saw moves forward.

 

[bobtskutter]

I still don't understand how a metal disk 2.2mm thick and spinning at 6000+ rpm can deflect, but OK.
Reading the original post again, do we know what's going on.  "consistently deviates by...over a 3ft cut" doesn't actually mean the cut is bowed.  It could be the cut is 1/32-1/16 away from the splinter guard, it might be straight and the splinter guard could be trimmed too much and unevenly.

Please can we have some pictures that show the problem?

Regards
Bob

 

[Svar]

I still don't understand how a metal disk 2.2mm thick and spinning at 6000+ rpm can deflect, but OK.

Look at zero clearance insert on a table saw. After some use it will be chewed up a millimeter or more on both sides and have distinctive tooth marks. It's because blades deflect when in use for variety of reasons: knots, misaligned fence, poor technique, wood grain direction, etc. Same with splinter guard on the guide rail, it wears out over time because the blade deflects for the same reasons.

 

[bobtskutter]

Ah, OK.  Now I get it.  My table saw sled has those marks and so does the splinter guard on my rails.
Thanks
Bob

 

[Crazyraceguy]

I set mine to zero too. When you are cutting really thick material, the blade will really start diving toward the rail. I had to replace the splinter strip on my FS1400 because of it, the first time I cut that deep. It still had the factory setting of the toe, at that time.

 

[mino]

I set mine to zero too. When you are cutting really thick material, the blade will really start diving toward the rail. I had to replace the splinter strip on my FS1400 because of it, the first time I cut that deep. It still had the factory setting of the toe, at that time.

This.

I guess this "recommended toe-in" is a carry-over from the times where the rail cams were of the old type. The idea being that one will get a bit better accuracy (cams a bit loose by necessity) on a long cut if the saw is gently "pushed" in the direction of the track reference edge.

With the updated cams on the TS 55 R and newer saws that have an "elastic" zone, this concept is just obsolete in my view. It may still work fine with sheet goods, but should not be the "factory setting" anymore.

Completely forgot about it by now. I have used a completely parallel blade ever since spending the month of sorting out all kinds of accuracy challenges coming from technique and what not when I got my TSC.

 

[bobtskutter]

FYI, this post was about a TS75, which has "old style cams" where the aluminium saw base is in direct contact with the reference edge of the guide rail (at least my TS75 does).

Regards
Bob

 

[semenza]

Hi, [member=82175]Kerfmaster[/member]

          Welcome to the forum!  [smile]

    What are you cutting?

Seth

 

[Kerfmaster]

Hi! Thanks. Long time lurker. Big fan of this community.

I’ve run into this with both sheet goods and hardwood. Plywood, MDF, walnut, maple. All the same problem.

 

[Kerfmaster]

I still don't understand how a metal disk 2.2mm thick and spinning at 6000+ rpm can deflect, but OK.
Reading the original post again, do we know what's going on.  "consistently deviates by...over a 3ft cut" doesn't actually mean the cut is bowed.  It could be the cut is 1/32-1/16 away from the splinter guard, it might be straight and the splinter guard could be trimmed too much and unevenly.

Please can we have some pictures that show the problem?

Regards
Bob

I’ll send some pictures next time I’m cutting some sheet goods. The reason I know it’s not due to rail issues is that 1. The rails are brands new and I tested them like I’d test a square (drawing parallel lines side by side and measuring deviation), but 2. I’ve also run the saw repeatedly against a perfectly tight Woodpeckers 26” square. Same issue no matter what.

But the input here has me wondering about the merits of toe-in. I’m going to recalibrate my saw for zero toe-in and I’ll see if that changes anything.

I really really really appreciate everyone’s time and wisdom on this. An even more thoughtful and engaged response than I’d hoped for. Truly a testament to this community thank you!