Replaceable carbide blades

spoilboard cutters

use for spoilboard surfacing or surfacing timber on a router sled

blades have four cutting faces.

five shank diameters

6mm 6.35mm 8mm 12mm and 12.7mm

two, three, four or six blades round the outside and

sometimes two flat blades on top ( listed as 2 + 2 for instance

these will potentially last a lifetime, the replacement blades are easily available and

cheap, 

these will not plunge,

To use.

run the cutter back and fore with about one third overlapping the previous cut

smaller shanks are more likely to slip down and spoil the piece so tighten well

wider cutters obviously require more capable machines or shallower passes

but work faster and have fewer overlaps but need more accurate vertical alignment.

2+2 cutters give a smoother surface.