Abstract: A chair fastening device for securing a metal bracket to a seat pan of a chair thereby enabling arms, legs or pedestal bases with or without control mechanisms to be attached to the chair. The fastening device comprises a slab base weld nut which includes a slab base head that is captured and retained by parallel raised ribs formed in the plastic of the seat pan, thereby preventing rotation of the slab base weld nut, and an elongated barrel which is inserted through angled holes in the plastic seat pan and peened over in order to form a rivet connection with the underside of the plastic seat pan. The elongated barrel of the slab base weld nut is counterbored and further includes internal threads adapted to receive a screw or bolt for use in securing a metal bracket to the plastic seat pan without inducing stress fractures in the plastic, thus creating a strong, secure attachment for chair arms, legs or pedestal bases.