Band Saw Fence Vertical Alignment
Board Cut Accuracy
Let's review what happens when your fence is not perfectly perpendicular to your band saw table surface. For example, let's say your existing fence is out of perpendicularity by 1 degree to table surface. For each inch of board rise (i.e. board height) the cut will be off by 0.0175 inches, top to bottom.
Let's assume you are re-sawing 8 inch tall board. The cut offset from the top to bottom will be 0.140 inches (x = 8" x 0.0175) per board. That adds up to 0.280 inches of wasted wood per cut! If the fence is off 2 degrees, the offset per board is doubled.
It has been my experience that fixed fences made from extruded aluminum or plastic will be at least 1 degree out of perpendicularity. Sometimes more.
Before using any fence, best practice dictates that you adjust the table perpendicular to the blade.
Band Saw Fence to Blade Parallelism
Board Drift
The illustration to the right shows unwanted board movement during cut operation. There are many reasons for this drift. Parallelism between the fence, table, and blade is one of many possible causes.
Before tuning your band saw fence and table-to-blade parallelism, follow manufacturer's band saw setup instructions.
How to fine tune parallelism between the fence, table and blade:
Step One: Adjust the fence parallel to table slot
Step Two: Using a sacrificial board, make a test cut to observe movement of board in reference to the fence
Problem A: Board drifts away from the fence as it is being fed into the blade. Loosen the fasteners holding the table. Rotate the table clockwise direction. Repeat test cut and table adjustment until the fence is parallel with blade. Rotational adjustments are done in small increments.
Problem B: Board is jammed against the fence as it is being fed into the blade. You will notice considerable resistance to feeding the board through the cut. Loosen the fasteners holding table. Rotate the table counter clockwise direction. Repeat test cut and table adjustment until the fence is parallel to blade.
Comments:
Out of parallelism is exaggerated in this illustration. In reality, if the fence-to-blade mismatch were this severe, the board would bind between the fence and blade.
