a pair of the opposed slots 16 an underside 34 of the blade cutting edge portion 32 is engaged by the surfaces 21 21 39 of a pair of the spring fingers 17 17 39 simultaneously a surface of the blade base portion 30 is engaged by the rearward surfaces 23 23 39 of the finger end portions 19 to urge the blade base portions rearwardly in their slots 16 as shown in fig7 lower edges of the slide portions are spaced from the bottoms of their slots to permit movement of the blades further into the slots 16 against the bias of the spring fingers 17 17 39 on which the blade base portion rests the spring fingers supporting the blade base portion 30 comprise another set of spring fingers the object of which is to resiliently support the blade means thereon and urge the blade means into a secure position within the slots 16 in the embodiment illustrated the blade means include a second blade 28 39 having a base portion 30 39 a cutting edge portion 32 39 extending at an obtuse angle to the base portion 30 39 and slide portions all anchored similarly to the above described first blade means the slide portions of the second blade are received in a third pair of the opposed slots 16 nearest the cap portion 14 with the cutter portion 34 39 resting upon spring finger surfaces 21 21 39 and with rearward finger surfaces 23 23 39 bearing against the second blade base.