Makita 118" Rails for Makita Plunge Saw Issues

[David Buchhauser]

I think that a 1/8" bow in the edge of your guide rail would (or should) be very apparent by just sighting down the edge with your eye. You could also position your guide rail so that the edge faces up and clamp it in a vise using soft jaws or blocks of wood to prevent scratching the guide rail. Then pull a string tight from one end to the other. If the edge of the guide rail is bowed, this simple test will certainly show it.
David

[Dave Sabo]

Like I said , your rail may be garbage anyway.

Does your “accurate” straight edge show a dip in the rail or counter top in the same spots on both the counter and rail ?

What does the straightedge show on the inner spine at the same spot as the pictured dip ? That’s the one that the saw actually registers on.

Are there other dips or bows along the rail ?

That end of the rail should be hanging off of an 8’ sheet by at least 8”-12” anyway - effectively taking the curvy end out of the equation.

Don’t use the TSO square for the first long cut.

As mentioned , clamping is a good practice.