Using a miter gauge without an auxiliary fence is like
wearing a pair of trousers without suspenders (or a belt) – you just don’t get the support you need.
And while it’s pretty easy to just screw a piece of wood to the front of your miter gauge, I think it’s worth taking just a couple minutes to make an adjustable auxiliary fence. This way, you can move the fence as close to the blade as you want, even when mitering, see Fig. 2.
JIG CONSTRUCTION. The “adjustable” part of the fence is made up of two sliding pieces, see Fig. 1. A rabbet cut on each piece allows the two pieces to interlock.
The top piece has a couple of threaded inserts so it can be attached to the miter gauge with machine screws, see Fig. 1a.
The bottom piece “floats” under the top one (until the two machine screws are tightened). By sanding the top piece 1/32″ thinner than the bottom, it will “pinch” the bottom piece in place, see Fig. 1a.
A replaceable face is screwed to the front of the bottom sliding piece. This way, when the fence gets chewed up, you can make a new one.