HM Dado circular saw blade set for grooving D 250 mm

slot cutters for the router here is a link to cmt ukproductscmt-router-bitsslot-cuttersslot-cutter-set-3-wing

In Router I have a simple rectangular part that has a dado cut that is 34 wide and 12 deep through the middle of the part

job slot Yesterday I cut a dadoslot in the backboard I wasn't sure I would do it right but the end result is what I need

how to tell when slot machine will hit Planet-Wattohm Logix White Dado Trunking - Closed Slot, W130 mm x D50mm, L2m, PVC ; RS Stock No : 399-6459 ; Brand: Planet-Wattohm ; Manufacturers Part No : 48006