straight edge jig for table saw == fail fail fail!

[Northernlight]

Hi guys.
So i made a simple jointing jig for my table saw with a piece of mdf that i put a straight edge on using the festool track saw, drilled some 30mm holes in it with a forstner bit and milled out slots on the underside to accept festool clamps.

i want to take a 2x4 and rip it down to 35x35mm and i start off with running side A in the jig. I then flip it 90 degrees and put side A towards the bottom of the jig. After that i rip side B and voila. Instant perfect 90 degree cut. And now i have 2 sides that are at a 90 degrees to each other and this should be very easy to run through the table saw to make the other 2 sides perfectly straight and at 90 degrees to each other.

But 1 side always come out at 92-93 degrees and that is frustrating. Anyone got any ideas as to what is wrong?

 

[Hunter]

Sounds like maybe your table saw blade isn't vertical, but instead is running something like .75 degrees off?

90 + 90 + 90 + 90 = 360 but 89.25+ 89.25 + 89.25 + 92.25 = 360

 

[dltflt]

Could the piece be tilting slightly when you clamp it?