Joining two Festool rails

[ian maybury]

It seems to me that it's very much a matter of what you define as a 'problem'. The basic issue is that the two joining rails are placed very close together, with the result that any pressure that tends to knock the halves out of alignment is turned via the leverage created by this short distance into a pretty heavy force that tries to slide one or both rails along its slot against the grip obtained by the screws.

That grip cannot be great, because there are definite limits to how much you can tighten the screws without damaging the aluminium rails. It might work better if there was some sort of a detent hole where the screws bear, but then those holes would have to be very precisely placed and/or the end faces very square or they would simply act to pull the rails out of alignment. Drilling and tapping for some extra holes would probably help too.

That's not to say that it's too hard to get the system to work perfectly well, and the zero clearance and backer-like function of the rail means that it delivers beautifully clean cuts too.

It does tend to mean though that careful handling of the assembly is needed, especially if it's rotated so that the face of the guides is vertical, with the joining rails to the bottom. In that situation it doesn't take much of a bump for the screws to slip and the rails to move out of alignment.

The guy in this video in demonstrating the system precisely explains what's needed to avoid problems - you basically need to (a) ideally work on a flat table so that the joint is not stressed as above, and (b) to frequently check the alignment with a straight edge:

http://www.youtube.com/watch?v=pVFuP...eature=related

That's fine if the sort of work you are doing only occasionally requires long rips. If I was going to set up along the lines that this guy has to use the system for frequent ripping then I'd want to go with the one piece 3m or whatever rail it is that he has too - checking alignment would wear thin pretty quickly:

http://www.youtube.com/watch?v=NiAr7...endscreen&NR=1

ian

[Will Blick]

The screws.... I think they use the fat flat heads, cause they don't want you to over tighten, as the thin metal dimples, which can create problems when the area is all dimpled, assuming you over-tighten, which is easy with allens...

as for the youtube, yep, he uses a long straight edge... I think this is one area where Festool could have been more precise with the 90 deg cuts on the rails...you would think, with two perfect 90's, the joined rails would be dead straight. In my case, they are NOT, unfortunately. But if I tinker with it with a good straight edge, its good to go. Then, set it down on its end too hard, you can change the position without knowing it...like most people, I now use a single rail for all cuts, yes, multi rails are costly, but it eliminated this issue forever. I get tired, and hate to check, re-check, etc. It sounds by the way these posts are going, others got rails which were cut at perfect 90 deg. so the ol, ymmv, might apply here... but these posts make everyone aware of the situation.

[ian maybury]

Working with my set last night I noticed that the end/cut faces are definitely not quite square on them either - with the joint set up using a straight edge and the screws tightened down there's a gap of about 0.25mm to one side....

I'm figuring this could probably be cleaned up and made square on the table saw, but it'd need the cross cut to be very accurately set to 90deg.

ian

[Jeff Monson]

There is no need to use straight edge or any complicated tricks to get the rails to align. Simply do what Festool refers to as bridging the gap. On the right side of the saw plate there is a V shaped mark about halfway between front of plate and back. Center this over a small gap left between two rails. Tighten cams on left side of saw and that pulls tracks into alignment! Tighten connectors and your off to the races.

Chris

Thanks for the great tip Chris

[Will Blick]

Using the saw as a straight edge has limited application. I would only trust this on the shortest rails, maybe... if you join two 4-5ft rails, the errors magnify with distance, the relationship is linear, double distance = double error. The saw is only extends maybe 10" over each rail. When you rip an 8ft sheet, the errors can become very noticeable, specially if you are joining the two edges.... A simple straight edge, even if low cost version is hard to beat...and faster.