Than the largest diameter of the mandrel. The workpiece is forced endwise on to the mandrel. The gripping force between the workpiece and the mandrel is created due to the taper on the mandrel.
(ii) Straight mandrel. It differs from the taper mandrel in that it has straight or untapered chucking surface. To press fit the workpiece on to the mandrel, the outer diameter of the mandrel is made bigger than the bore of the workpiece. The difference known as interference depend upon the wall thickness, diameter and the material of the workpiece. It should not be too large to cause plastic deformation of the mandrel and/or of the workpiece.
(iii) Combined taper and straight mandrel. In this type of mandrel, a portion of the outer diameter of the mandrel is straight and the rest is tapered. The straight portion helps to prealign the bore of the workpiece and the tapered portion provides the driving area on to which the workpiece is press fitted.