Hi. Welcome to the forum.

 

As close to the insert as you can get it. However, unless you intend to use it for a feather board I wouldn't bother. A sled works better in my opinion and requires no setup. If you intend to use a mitre gauge and use the fence at the same time they have to be square to each other and the bit exposure has to be right at the same time which can take a while to get right. With a sled you only have to worry about the bit exposure. The sled takes care of the squareness for you.

 

However, unless you intend to use it for a feather board I wouldn't bother.

Plenty of uses for a miter slot/track.

Incra Ibox is one. Another would be a circle cutting jig. Even think about a cross-cut sled for angled slots/grooves.

However not an essential add-on.

 

A "typical" distance is usually about 6".

 

Check on the Incra web site. If you decide that you want to use one of their jigs then you have to be within a certain distance. Might as well plan on it because it won't matter if you never get one but will matter if in the future you decide you want one.

 

From the center of the T-track to the center of the router bit should be between 6" and 6 1/2'' This is the measurement Inca and Kreg uses.

 

Just leave room for the pin an Welcome Donn48

 

From Mark Mueller himself;

"On our tables, the miter channels are centered 6" - 6-1/2" from the centerline of the plate"

 

There are differing schools of thought on miter slots/T track. They tie you to specific locations which is good for Incra jigs. Clamping your jigs in place gives you unlimited positioning choices not tied to these locations. This is the keep it simple method taught by Bob and Rick Rosendahl of the Router Workshop. To the best of my knowledge Bob was the first to design a miter sled specificaly for router table use and it guided off the fence.