3000mm Guide Rail curve

[Trans former]

I think brice is right don't be shy give it a bit of a whack.. or evan a little push should do it.

I am also finding lots of types of board material with internal tension or spring where the just cut board no longer matches up evan in birch ply and mdf, thought it might be something to do with our continuously changing crap weather.

just realised this is a very old conversation i'm adding to but hey ho.

 

[nanook]

So whats the Festool spec on guide rails for straightness?    
If there is not one - would Festool USA warrantee a new undamaged rail with this amount of deflection? [scared]

 

[FulThrotl]

So whats the Festool spec on guide rails for straightness?    
If there is not one - would Festool USA warrantee a new undamaged rail with this amount of deflection? [scared]

well, the simplest way i could think to check straightness is to lay the rail on a
flat surface, clamp a piece of fishing line onto one end, go around the
guide rib, and pull it tight over the length of the rail, and see if there is a gap,
if there isn't, put the fishing line on the other side of the guide rib and
check for bow in the other direction.

ripping corian for a backsplash, i was doing 8' rips with two guide
rails joined together, and i took two rips, flipped them 180 degrees,
touched them together, and measured the gap in the center of the
span with a feeler gauge, and it was about .010". so that's straight
within .005".

 

[Nick C]

Must be an interesting topic--the thread has been active for a long time. I think 1/32" error in10' for a Festool guide rail is acceptable. Barely. The rail does not have the beam strength to resist a minor amount of deflection. Just for reference: You can buy a PaveFlat brand aluminum precision straightedge that's 10' long. Assuming it is stored and handled properly (not easy to do) it will be straight to within 0.012" over its 10' length. It costs about $1300.

 

[greg mann]

Thanks for the quick reply.  I am not using the 3000mm rail on the MFT - I think I explained it poorly.
I am using the 3000mm rail to make rip cuts on 4x8 sheets and then I am moving my ripped pieces to the MFT/3 where I cross cut them (with the standard guide rail).  Because the freshly cut edge of the ripped piece isn't straight, its indexing on the MFT fence incorrectly if that makes sense.  I do not have an accurate straight edge long enough to test the guide rail but marking and line and then flipping the rail 180 degrees should be an adequate test, right?

As far as the technique goes, I don't believe that I'm bending the rail.  And marking a line along the length of the rail with a pencil doesn't exert any force to bend the rail...

Not to beat a dead horse but I have read and re-read a couple times some of the responses here. In one case the claim was made that the original error would be multiplied with additional cuts. The reality is actually that the error gets reduced with each subsequent cross-cut. The OP has a cut which is out approximately 1/32 over 10 feet. (Just for reference this is an arc with a radius of 5000 FEET.) However, when he places the piece against his MFT fence he is using, what, maybe 5 feet? Therefore his reference length is now half as long, and can only 'see' half the deviation in straightness. He references cutting 4x8 sheets so .032 error at 10' equates to .025 at 8 feet. Crosscut that at 4 feet and the error is now about .012 in straightness. Not so much.

Based on the understanding that the stock is going to be crosscut I would suggest that if absolute accuracy is paramount, crosscut first. Then shorter rails can be used, set-up hygiene is easier to confirm, technique becomes less of a variable, etc. This is somewhat aligned with the advice to cut stock reasonably close to its finished length before jointing, leaving enough to remove snipe if you experience that problem. It wouldn't make a lot of sense to joint an 8 foot board to perfection and then cut it to 4 two-foot lengths. Imagine how much grief involved in that process, not to mention waste.

I know this may seem anathema to someone who has spent good money on a 10 foot rail but.....? I have one too, rip the length first, don't check for straightness, crosscut my stock off that edge, and never find any subsequent problems that would lead me back to that original cut. Maybe I have one with a 10,000 foot radius.  [cool]

 

[Bob Gerritsen]

Well, I've just found out my 3000 rail has a curve and went online to find this thread. I cannot find any response from Festool or anything conclusive on the tolerances, that is too bad.

I've just spent a good hour ripping a piece of particle board to about 360mm wide. It came out 1mm wider in the middle over a length of 2400 mm, meaning the rail has a curve of half that over that length, a bit more if you count it's complete length of 3000 mm. Maybe not a lot for most situations or users but unacceptable for this occasion, in fact it makes the rail rather useless for what it is usually meant to do in my case. My rail is never dropped but I have to say I've doubted it's straightness more than once. This time I ended up really getting to the bottom of it and now I'm sure. I've used the data from cutting the sheet and double checked using a long extrusion than I ended up using to get a straight cut btw, in any case, it is bend.

So anybody have any idea what Festools policy is? My rail is out of warranty but I would like to know in light of possibly getting a new one.

Also, can anybody tell me with 100% certainly how aluminum such as these rails can respond to temperatures? In other words, could close to 100% straightness be too much to ask with changing temperatures?

Cheers, Bob.

 

[Bob Gerritsen]

Thanks for the quick reply.  I am not using the 3000mm rail on the MFT - I think I explained it poorly.
I am using the 3000mm rail to make rip cuts on 4x8 sheets and then I am moving my ripped pieces to the MFT/3 where I cross cut them (with the standard guide rail).  Because the freshly cut edge of the ripped piece isn't straight, its indexing on the MFT fence incorrectly if that makes sense.  I do not have an accurate straight edge long enough to test the guide rail but marking and line and then flipping the rail 180 degrees should be an adequate test, right?

As far as the technique goes, I don't believe that I'm bending the rail.  And marking a line along the length of the rail with a pencil doesn't exert any force to bend the rail...

Not to beat a dead horse but I have read and re-read a couple times some of the responses here. In one case the claim was made that the original error would be multiplied with additional cuts. The reality is actually that the error gets reduced with each subsequent cross-cut. The OP has a cut which is out approximately 1/32 over 10 feet. (Just for reference this is an arc with a radius of 5000 FEET.) However, when he places the piece against his MFT fence he is using, what, maybe 5 feet? Therefore his reference length is now half as long, and can only 'see' half the deviation in straightness. He references cutting 4x8 sheets so .032 error at 10' equates to .025 at 8 feet. Crosscut that at 4 feet and the error is now about .012 in straightness. Not so much.

Based on the understanding that the stock is going to be crosscut I would suggest that if absolute accuracy is paramount, crosscut first. Then shorter rails can be used, set-up hygiene is easier to confirm, technique becomes less of a variable, etc. This is somewhat aligned with the advice to cut stock reasonably close to its finished length before jointing, leaving enough to remove snipe if you experience that problem. It wouldn't make a lot of sense to joint an 8 foot board to perfection and then cut it to 4 two-foot lengths. Imagine how much grief involved in that process, not to mention waste.

I know this may seem anathema to someone who has spent good money on a 10 foot rail but.....? I have one too, rip the length first, don't check for straightness, crosscut my stock off that edge, and never find any subsequent problems that would lead me back to that original cut. Maybe I have one with a 10,000 foot radius.  [cool]

Greg, I understand the point your making but the long and short of it is you're going to run into problems at some point with a rail that is bent like that. In my case, I need to end up with 2 pieces of 2100x359 mm that will be side to side along the 2100 mm's. As both pieces would end up 1 mm wider in the middle, 1/2 a mm per side, I would end up with 1 mm gaps on the two ends when those parts touch in the middle. That sucks. A 1 mm gap is quit visible. What sucks more is that there is nothing I can do about this. Regardless of how I turn the pieces, I have to cut them like that and end up with this curve. No matter how careful I am.

Cheers, B.

 

[tbellemare]

Is it possible to cut the joints simultaneously so they deviate the same way?

Tom

 

[Distinctive Interiors]

That is what I did Tom when I questioned the straightness of my 3000mm rail.

I was fabricating a large section of solid surface material for a kitchen island top. It needed a join right down the middle and had a finished length of 2600mm.

I initially cut the 2 edges separately, tried the joint by pushing them together and found a 1 to 1.5mm gap in the middle [huh]

After a lot of head scratching and checking the LHS of the rail for straightness with a 2000mm quality spirit level, I found that the rail was straight!!!!

I came to the conclusion that the rail  was deflecting by .5mm per cut due to the fact that there was NO sideways clamping in the centre of the rail. With both ends firmly clamped, I pushed sideways on the centre of the rail and found a fair amount of sideways deflection. Even cutting the material in 2 or 3 depth passes didnt seem to make any difference.

In the end I came to the conclusion that I was perhaps expecting TOO MUCH accuracy from the FS3000. I then went out and purchased the Gecko and rail adapter and decided to cut both sections of material at the same time whilst butted up against each other. Taking 1.1mm of each sheet at the same time.

Since then, I have had to fabricate various tops in this manner and have not had any further problems.

I know the Gecko doesnt work on bare MDF or Plywood, but a simple clamp and a scrap section of timber pushed up against the LHS of the rail will prevent it from moving to the left while running the saw along. I would be very surprised if anyone here, who questions the straightness of their long rails, has found the rail makes a cut wider at the ends as opposed to the middle.

Just my 2 cents worth!!!!!! [big grin]

Tim.
 

 

[greg mann]

Great points, Tim. Perhaps that is why Mafell developed their self-propelled track saw. There are now two thread running in parallel (pun intended) about this. Your advice to stabilize the rail in the middle to see what effect that has is on target. If someone has suspicions of their rail they should do this as a way to isolate the root cause of their issues. Your decision to change your technique to compensate for conditions you found is to be applauded. I make my living developing processes run on equipment capable of accuracies woodworkers could hardly contemplate. Wanna know what my single greatest challenge is? Eliminating distortion, either from workpiece clamping, stress relief, or temperature fluctuation, and probably a few other sources I have yet to uncover.

You have suggested a path for Bob to solve his necessary use of a long rail. I hope he gives it a try. When the finished part lengths are not that long i am going to reiterate my suggestion that cross cutting earlier in the fabricating process will mitigate the need for absolute straightness over that extended length. What is easy to overlook is that a ten foot rail is not half a rigid as a five foot rail. It is four times less rigid. That can be a huge factor in the influence of technique. Pristine tools and accessories are great. If I didn't believe that I would not be a Festool junkie, but my day job constantly reminds me that it is the results that counts and it isn't always the equipment that has failed. In fact, it hardly ever is. It's the process.

 

[Bob Gerritsen]

Is it possible to cut the joints simultaneously so they deviate the same way?

Tom

Thanks Tom, good idea but it won't work in this case. Also, I simply want to be able to cut straight. So much so I'm willing to get out the cash and buy another rail. Unless of course there is no telling when this new rail will start to bend.

Thanks though.

 

[Bob Gerritsen]

To Tim and Greg, thanks for responding. I will check the Gecko method for sure but for me that won't change much of what seems to be the problem. I need a method to repeatedly and quickly cut sheets up to 2800 mm long. If it turns out the rail method means I have to check the rail before each rip cut and compensate for bend using the Gecko and then check the sheet for straightness after the cut I'm loosing money. A 2800mm rip cut should take less then a minute, not several minutes and even then the chance you have to try again. That might be ok if you make a couple cuts every now and again but I need a quick and reliable method.

In general I simply want to explore right now if this problem is typical for a rail this length, if the problem might reoccur with a next rail. If it is just something that comes with using rails.

Also I would like to understand what the margins or conditions are, why this happens. Then maybe I can think of a way to keep using the long rail in a for me acceptable manner. Trying to get the bend out is certainly an option but then what will happen when the temperatures rise again? Will the same thing happen only the other way?

So in short I'm not convinced at the moment that the solution for me is in the process. Or let me add some nuance, if the process involves checking your tools every time you use them, it is not the process for me. I always figured as long as you don't use sideways pressure, meaning if you use the right process with this tool and don't drop the rail, these rails would cut straight. Right now I'm just not sure.

Has anyone ever contacted Festool on the matter?

Thanks for the feedback so far.

Cheers, Bob.

 

[Bob Gerritsen]

Just got word from Festool Switzerland. The tolerance for a 3000 mm FS is 1.5 mm which is about 1/16th of an inch.
So the amounts of curve discussed in this thread fall within Festools margin. For whatever that's worth but at least it would seem to me they won't accept the return of rails within that margin.

I still would be very thankful to hear from any aluminum pro's or engineers to get a better understanding of how aluminum like the FS rails might curve with cold or heat.

Cheers, Bob.

 

[Bob Gerritsen]

So I've asked Festool what to expect with regards to temperature differences with the rails and if I'm correct that the margins also applies to the guarantee. Will let you know once I get a mail back.

Meanwhile spoke to Mafell Germany and got put through to what seems to be one of the inventors there, he promised me a 0,6 mm tolerance with two 1600 mm rails put together over the total of 3200 mm. Any more than that and he will accept a return and fix them. He gave me his name and direct number so I think he is serious about it.
Not mentioning that to put Festool down or anything, just reporting what I've found out so far. In the end I do need a solution that is guaranteed or I keep running into the same issue so who knows, I might have to consider that. Meanwhile I have to figure out what tolerance works for me.

Cheers, Bob.

 

[Bob Gerritsen]

Sorry, me again. I'm not getting any work done here  but just got a call from Festool CH which was interesting.

So temperature does not affect the straightness of the rails according to Festool. Meaning, in my own words, once you have a good rail and be gentle it stays good. That's good news.

Then, Festool CH is willing to send me another rail so I can compare and return the one that is the most bend. That's pretty cool. The idea being here that within the margin of 1,5 there still are better and worse rails right?

I told him I would take the time end of the week to really measure what the bend is over 2800 mm of mdf, using clamps on the ends to avoid any movement, measure the bend and call him after that. I'm hoping he can have someone check a couple rails to have them send me a really nice one, otherwise i might receive one that is the same or worse and it will be a back and forth of sending rails.

Anyway, good news I think, thought I'd share that with you.

To be continued.

Cheers!

 

[Festoolian]

Maybe you have an issue with rail placement technique.  Identify if your method is similar to what I describe below.

When aligning the rail at each end, the rail is slid onto the mark.  The rail is moved from the ends.  The middle of the rail is sliding against the rubber pads that are meant to hold it in place.  If the 3000mm rails is flexible enough, drag against the rubber pads could bow the rail slightly in the middle producing the concavity in the cut.

Try adding a reference mark in the middle of the cut.  Align your rail as usual and observe if the middle of the rail aligns to the reference.  If not, lift the rail slightly in the middle and release.  Recheck the alignment to the reference.  If your rail is straight, it should be on the mark.

Side bar:
Joining two short rails together should produce a rail that has less error than one long one with the caveat that they are aligned properly.  The joined pair should also be stiffer in the middle due to the steel joining bars.

If all rails are made with the same effective radius of curvature, then two short curved rails realigned where they're joined will accumulate less total error (chordal deviation from the arced rail to true straight) than one long rail.  The error will be located twice as often however (1/4 & 3/4 rail length) rather than a single central location. 

 

[Bob Gerritsen]

Thanks Festoolian, good points. I'm aware of the risk of curving the rail when pulling it to it's marks on the ends, I try to always end with lifting it at one end and then drop it on the mark to compensate for that. However, I plan to do some final checks end of the week, maybe the weekend and I'll pay extra attention to placement. Right now I've simply concluded the rail has a curve, both by the result of the cut as by holding an aluminum reference extrusion up to it (and flipping it and measure again to make sure the reference is actually straight).

Cheers.

 

[galwaydude18@gmail.com]

Side bar:
Joining two short rails together should produce a rail that has less error than one long one with the caveat that they are aligned properly.  The joined pair should also be stiffer in the middle due to the steel joining bars.

I just read this and it came me why not used a set of joining bars in the middle of the 3000mm rail. It should prevent the middle from bowing out as the joining bars will stiffen the rail up in the middle

 

[Distinctive Interiors]

Sorry Galwaydude, but I would have to disagree with you there.

It would only make a difference and add some more rigidity to the long rail if the joining bars were almost the full length of the rail.

Tim.

 

[galwaydude18@gmail.com]

Would it not help stiffen the middle of the rail and help prevent it from bowing out with sideways pressure or at least lessen it