Hello all. I am looking for a collet chuck that is 1/2" X 20 machine thread on one end and will accept a 1/2" shaft router bit on the other (in a collet). Does anyone have a link or connection online to where I might begin to look for said item? This adapter will fit my radial arm saw auxilary drive to use router bits. Sears makes one but it only holds 1/4" shaft bits. Thanks......