in fig2 is preferably tapered from a relatively small dimension adjacent the free extremities of the arms 35 36 to a larger dimension substantially equal to that of the skirt 38 in that portion 40 of the flange 39 which extends across the base portion 34 the cylinder bed free extremity 50 provides one bed extension locating surface on the sewing machine frame the upper surfaces 22 of projections 20 provide other bed extension locating surfaces spaced from and related to the free extremity 50 by an angle a the flange portion 40 of the bed extension 30 provides a first segment of the bed extension which is shaped complemental to the free extremity 50 of the cylinder bed the arms 35 36 of the u shaped work supporting plate 31 are each provided at their free extremities with a down turned lip 42 the lips 42 are complimental to the upper surfaces 22 of the projections 20 and extend the same dimension beneath the bed extension work supporting surface 32 as the upper surfaces 22 of the projections are disposed beneath the work supporting surfaces 15 and 16 on the sewing machine bed the bed extension 30 is formed such that when these bed extension segments 40 and 42 are positioned abutting their respective locating surfaces 50 and 22 in contiguous relation thereto the planar work supporting surface 32 of the bed extension will extend coplanar with the cylinder bed work supporting surface 15 the flange portion 40 however is formed with respect to the planar work supporting surface of the plate 31 of the bed extension at a smaller angle b than the angle a which the cylinder bed free extremity 50 makes with respect to.