a machine element arranged, in use, to lie opposed to and spaced from a roller of the spinning preparation machine and having a working portion and opposed first and second end portions, there being provided a first machine element bearing surface on said first end portion and a second machine element bearing surface on said second end portion; and

first and second machine bearing surfaces associated with the spinning preparation machine; wherein said first machine element bearing surface and said first machine bearing surface co-operate to form a first adjusting structure and said second machine element bearing surface and said second machine bearing surface co-operate to form a second adjusting structure, said machine element bearing surfaces and said machine bearing surfaces each being inclined and a direction of inclination of the inclined surfaces being substantially the same in each of said first and second adjusting structures, whereby on thermally induced expansion of the machine element in a longitudinal direction relative displacement along the inclined surfaces can take place in such a manner that a spacing of the machine element from the roller can be maintained substantially unchanged.