Sometimes I need to move the fence on my table saw a very tiny increment, but it either moves too much or too little, and I waste a lot of time getting it just right. I decided to make two identical triangles that slide against each other to increase or decrease their aggregate width. The photo shows how I adjust the position of the fence.
My table saw is a good quality circular hand saw mounted under a plywood table top that rests on saw horses. See the next steps for how I align it and set the fence so it is parallel to the blade.
- 1/2 inch plywood
- Table saw
- Taper jig
- Hole saw
- Measuring and marking tools
Step 1: Alignment -- Step 1
To align and set up my saw I use the saw's miter gauge and an accurate framing square. The first step is to set the miter gauge to exactly 90 degrees. Then I press the long side of the square against the face of the miter gauge. The other leg of the square should follow one of the miter gauge slots without deviation.
Step 2: Step 2 -- Check Blade Alignment
I have found by experience that "close enough" is not good enough. Move the framing square over to the blade and gently move it against the blade without putting pressure against the blade and possibly distorting its position. The edge of the square should follow the edge of the blade exactly.* The yellow arrows show where the square contacts the blade at the front and back of the blade.
*See the link to how I made my saw as given in the Introduction. I used adjusting screws against the base of the saw to align the saw. A quarter turn on one of the screws moves one end of the saw a couple of thousandths of an inch. I do check the position of the blade regularly because vibration from use can move the saw out of alignment.
Step 3: The Usual Method for Setting the Fence
Normally, I would place the square against the miter gauge and slide it until the dimension between the short leg of the square and the blade is the width of the cut I want to make. Then I would carefully clamp the fence (a piece of plywood from the edge of a sheet with a factory cut true edge) to the saw table. This works well until I need a very fine adjustment of 1/16 inch or less to get a cut just right. Then I often move the fence too much or too little.
Step 4: Setting Up the Fine Adjustment
I have an extra piece I sometimes use as a fence. It is one of the backboards from my radial arm saw's old table before I replaced the table. Its edges are parallel, too. I use the framing square to align it. You see it held in place with "C" clamps at the right of the photo. Next you see my two sliding triangles. Press them against the chipboard fence at the right. Bring the plywood fence against the triangles. Remove the square and miter gauge.
Step 5: Slide the Triangles and Measure the Cut Width
With no clamps on the plywood fence slide the triangles against one another until the cut width is just right. Measure carefully. Clamp the plywood fence in place. (I used a hole saw to make holes in each triangle so I can easily grasp the triangles for sliding them.)
See the second photo. I made a pencil line that crosses over the diagonal edges of the two triangles. The distance between them in the photo is almost 1/8 inch. Sliding the two triangles so the marks separated almost 1/8 inch moved the plywood fence 1/32 inch nearer to the blade. Adjustment can move the fence nearer or farther from the saw's blade in very fine increments.
Step 6: How It Is Made
I had a scrap of 1/2 inch plywood a little over five inches wide and about 30 inches long. I marked a cut line between opposite corners. Use a taper jig to make a cut that follows the line. I rubbed the sliding edges with paraffin to make the action smooth and easy.
(I do not have an actual taper jig. I used a sled I made for trimming an irregular edge from a piece of wood I might want to rip on my table saw. Here is a link to that Instructable. I used my rule to make an offset on one end that was equal to the width of the piece of was cutting. The blade very closely followed the cut line I had drawn.)