A slot cutter arbor is used to mount slot cutter in a router. The shank side fits into the router and the slot cutter is held on the other end with a hex nut. Slot cutter arbors are normally used with a bearing to control the depth of cut.

The 1/4" shank 108R-4 arbor by Dimar includes a hex nut and shims. Works with slot cutters that have an 8mm (5/16") center bore. A 7/8" OD bearing (not included) is commonly used to create a 1/2" depth of cut