Spiral bits cut timber cleaner than using a straight cutting, this makes cutting Leigh finger joints and Isoloc joints by far quicker and simpler using the slicing action that spiral bits have. The upcut action removes the waste from the cut efficiently, allowing the user a greater chance to see the joint as it is being cut.
Solid carbide cutters are more expensive to purchase, but will hold their edge longer. High Speed Steel cutters are a more economical choice for cutters, and hold a sharper edge than solid carbide, though their edge will not remain as sharp for as long.
Photo is indicative of the profile of the cutter.