Quote Originally Posted by Jonathan View Post
Sliding the gantry back and fourth and tightening the bolts to tweak out any tight spots also wont get the rails straight. It will merely copy any bend in the master rail to the subsidiary rail. Very few DIY builds rest the master rail against a reference edge, or indicate it to get it straight, hence for those any bend in the rail as shipped will remain (in one plane). For example if I just bolt down one of my 15mm rails to a piece of nice flat aluminum tooling plate, then use the sliding method to align and fix the other rail to the same plate, the error I measured will still be present so the measurement is relevant. That's what most people do and it's perfectly valid for supported rails.
In which case they have incorrectly installed them.!!!! . . . If the master rail reference edge is accuratly straight which it should be and is the whole point of having it then the subsidiary rail as you call it will be perfectly straight.!! . . If not used then you will have incorrectly installed them and defeated one of the main points of using profiled rails.!! Accurecy

I get the feeling Jonathan you haven't ever used profiled rails before.? Because if you had you wouldn't be so quick to argue with me about the bennifit of the master rail and having a straight reference edge. You would also know just how critical and intolerent the bearings are of miss alignment and poor mounting surface.!

If you have then you know I'm correct and pride is just making you deliberatly argumentative is all I can think.!!! . . . . either way your very wrong.!