Miter SledA new addition to the shop, I finished this little guy the other day in an effort to make perfect miters on the crown molding for the bookcase. It took all of 30-40 minutes to make and most of that time was spent on the runners. I only had 3/4" stock laying around so I pulled out a suitable sized sheet of particle board (i use this stuff alot) as my base. The runners and the miter fences are made from a length of 3/4" maple that was leftover after ripping the parts for the bookcase's face frame. Add a couple toggle clamps from Harbor Freight (horrible fright!) and we're in business!
Like I said, most of my time was spent on the runners. I tested them before mounting 'em to the base and they slid nicely in the miter slots of my saw. But when I attached them, it was a different story. Since the screws had to be countersunk, I had very little wiggle room to adjust them. Instead, I had a block with some sandpaper glued to it right up to its edge. After about 20 minutes of pushing, jamming, removing and sanding the dark spots, I finally had a sliding miter sled.
The rest was pretty easy. Once the runners were on, I raised the blade in the saw and cut a kerf about 2/3 into the base. This told me where to align the peak of a 90º fence. I cut 2 pieces of maple to equal lengths for the fence. With a mark 6-8" from the ends and a line on the base about 5" from the kerf, I aligned the marks and the peak together to make a 90º fence that was aligned as close to center as I could get.
Getting the fence lined up to make 2 perfect 45º wasn't as important as making sure I got a perfect 90º angle in the end. Any variance would be offset by the use of the jig: One piece is cut using the left fence. The mating piece is cut using the righthand fence. This will counter any slop in my angles since the fences are at 90º to one another.