hi, i bought a freud dado cutter and i have tried to fit it to my dewalt dw720 radial arm saw, but i cannot get the whole stack on with the nut to secure it because there is not enough room on the arbour, do i need a special insert flange to take the blade further in, looked everywhere on internet but cant find any specific part and also in the dewalt dw720 manual its not clear if you need so special flange insert before the stack is assemble, why sell freud dado cutter that states they fit dewalt radial arm saws? can any1 advise, thanks.