For a while I’ve noticed that when I rip a clean edge on my table saw and put it up against my fence, there’s a gap between the board and the fence. I’ll take a square to the edge and find out it’s perfectly square, shrug my shoulders, and continue what I was doing.
This happened again a few days ago, so this time I put the square against the fence and found that it was bowed — see the above picture. The fence is a piece of extruded aluminum between two mounting brackets, so trying to replace it was out of the question. What I needed to do was find a way to mount an auxiliary fence to the aluminum fence without getting in the way of normal operations. I had just the answer: T- slots.
So I cut a T-slot 1-1/2″ from the edge of a piece of 3/4″ MDF, then cut another one the same distance from the edge on the opposite side of the board. My thought was that if I ding up the fence I can just flip it over and use the other side. Plus I can use the slot on the face for mounting feather boards. Then I drilled two 5/16″ holes right through the aluminum fence, 1-1/2″ up from the table for two T-bolts. Now I can just slide the auxiliary fence right over the T-bolts and tighten it down.
Ahhh, not so fast, when I attached the auxiliary fence I found that it wasn’t square with the table. Evidently the bow isn’t symmetrical on the top and bottom so I added a few paper shims to push the bottom of the fence out slightly.