Guide Rail Transition Issue

[Maxim]

Hello! I just bought a TSC 55 REB, and 55” and 75” guide rails. I followed the instructions and videos to make the initial cut on the 75” rail after adjusting the knobs to remove play - no problems. When I switched to the 55”, however, the saw was loose and needed to be tightened. Problem that I’m running into is that at the 55” setup, the saw is way too tight for the 75” rail (it effectively won’t move). My plan is to join the rails so that I can cut full sheets of plywood, but I’m not sure how this could work given the different tolerances needed for each rail.

Has anyone run into this issue before? If so, have any suggestions? Apologies in advance if this has already been addressed - this is my first post and I’m tapping this out on my phone in a freezing garage.

 

[mino]

Yes, this can happen.

The rails are never exactly the same and this can cause issues.

Best thing you can do is take your rails (I am assuming these are new) back to the shop along with your saw and switch them for a "matching" pair of rails that have the thickness close-enough.

The other option is to set the saw based on the "harder" rail, start the cut with that and continue with the "softer/thinner" rail later on.

Be sure to check this - if you align the rails by the reference surface you will get still as good a cut as feasible given the slightly looser fit on the second rail.https://www.festoolownersgroup.com/festool-how-to/how-to-connect-and-align-festool's-guide-rails/

EDIT:
The saw cams have more play than the non-cam side (i.e. the reference surface). This is by design and ensures the saw will still be properly aligned even when the cams are not same-level-of tightness between the rails.

The reason the rails are not exactly the same is they are not machined - were they machines they would cost 2x as much and it would still not improve accuracy. The slight thickness variance is accounted for in the design of the saw's guiding system so it makes no practical difference.