Abstract: An adaptive holder for interconnecting a non-locking bit shaft in a locking bit chuck provides an elongate body having a locking bit shaft at a first end and a chuck connector at the second end. The locking bit shaft is of hexagonal cross-section with an annular fastening groove defined spacedly inward of its outer end. The body is formed of elastically resilient material. The chuck connector provides a second body end defining a hexagonal fastening channel and a threaded external surface operatively carrying an annular collet threaded from its inner end outwardly to a point spacedly distant from its outer end with plural imperfectly formed threads in its outer end portion to cause radially inward motion of the body second end to move along the imperfect threads to releasably fasten a non-locking bit in the channel. The second end portion of the body may define one or more slots extending through the body to the fastening channel to aid radial motion of the body to fasten a bit.