Abstract: A centralizing device comprising a plurality of blades and a pair of substantially cylindrical collars adapted to receive and carry the blades. Each collar is formed with at least two parts detachably and/or pivotally connected to each other, and each collar carries inwardly extending deformable metal fixing projections. Each end of each blade is bent substantially at right angles to a portion of the blade adjacent the end. When the blades are fitted so as to lie internally of the collars, each bent end fits into a slot in one of the collars and the projections are deformed so as to lie on the sides of the blade portions remote from the collars to thus fix the portions to the collars.