1381627 Abrasive tools J A BELANGER 13 June 1972 [23 June 1971] 27685/72 Heading B3D A pack unit adapted to be mounted on a rotary wheel hub structure 12 comprises a flap-like member of fill material 14 preventing a radially-outer finishing portion adapted to engage a workpiece, and a mounting member 32 distinct from the flap-like member for mounting the latter on the hub structure, the mounting member being relatively rigid and providing a single radially inner and axially extending portion 34 for mounting on the hub structure, and a radially outer and outwardly extending portion 33 integral with the inner portion and to which the flap-like member is fixedly secured. The hub structure 12 consists of a sleeve 15 which is formed with a flange 17 and in which is fitted a bearing part 18 having a bore 20 for receiving a driving shaft. Pins 26 are welded to the flange 17 and extend into apertures 28 in a disc 22 mounted on the sleeve 15. A plurality of pack units 14 are mounted on respective pins 26 and retained thereon by the disc 22 which is clamped in position by bolts 25 which extend into units 23 or threaded apertures in the flange 17. The mounting members 32 may be of extruded aluminium or plastic material and each consists of a body portion 34 having a partcylindrical opening 36 for engagement with a pin 26 of the hub structure, and a pair of arms 33 between which a stack 14 of finishing sheets, such as abrasives coated material, emery cloth, fabric, leather, sisal or the like, is secured by one or more staples 40, the stack being located by shoulders 39. In other embodiments, the openings in the body portions may be fully cylindrical and the shoulders are replaced by a single abutment surface or an intermediate arm is located between the pair of arms 33. In a further embodiment, the stack 51, Fig. 6, of fill material is folded about a pin 52 and the arms 53 are proivded with projections 55. The body portions may be provided with a notch (64, Fig. 7, not shown), or notches for receiving an intermediate plate or plates between the end plates of the hub structure.