the machine through suitable cylindrical holes in the pivot base 19 and frame of the machine 10 the rod 41 defines an axis of relative pivotal movement between the base 19 and frame of the machine 10 extending parallel to the axis of the hinges 31 the pivot base 19 is adapted to alternately support the machine 10 at two operational positions a frame arm position and a flat bed configuration comparatively illustrated in fig3 and 4 respectively a bolt or pin 46 mounted in the standard bed 28 is slidably guided by the surface of a cylindrical bore 45 within the rear of the standard base 28 and is adapted to be indexed into engagement with the surface of one or another of a pair of holes 47 and 48 in a vertical face 49 of the pivot base 19 associated with the notch 27 the bolt 46 is biased towards the holes 47 and 48 by a tension spring 51 operating on a lever 52 pivotal on a post 53 fig8 a shaft 56 has one of its ends connected to the lever 52 and its opposite end exposed through the wall of the standard to form a push button 57 the push button 57 is manually depressed towards the housing of the standard 14 against the force of the spring 51 to release the bolt 46 from either of the bolts 47 or 48 and allow relative pivotal movement between the base 19 and the frame of the machine 10 and thereby allow a change of the machine from one operational position to another in the lower or flat bed operational position of the machine 10 fig4 and 6 the upper bed surface 24 is substantially coplanar with an upper surface 61 of the cabinet panel.