Patent GB-557288-A (GB)
Title: A method of making stamping dies
IPC: B21D37/20
Filed: 1941-08-01
Abstract: 557,288. Surface and outline gauges. BUDD MANUFACTURING CO., E. G. Aug. 1, 1941, No. 9778. Convention date, Aug. 3, 1940. [Class 106 (ii)] [Also in Group XXII) A die for stamping motor car body or other cheet metal parts is made by machining a casting by a copy-milling machine roughly to the form of a model and then filting it to a negative gauge of the model by means of red lead or the like and scraping. There are also described methods of marking trim lines, for use in making the trimming dies, and of making a gauge negative and how this may comprise a main part which can be combined with auxiliary parts to form a negative of either the initial or the final die. Such a gauge negative 57, Fig. 6, is made by first building a base-frame 61, e.g., of mahogany, having its face 62, Fig. 7, an approximate negative of that part 38 of the model 54 which represents the portion of the stamping to be brought to its final shape by the first set of dies. Keying means such as nails 63, are then provided and the base 61 is fixed with its surface 62 spaced, e.g. # inch to ¢ inch from the face of the model, the gaps being closed by cardboard 64, adhesive tape 65, and plaster of Paris 66. Metal 67 of low melting point is then poured in to form a true negative and when this has set the parts are separated. Marginal base members 68, Fig. 8, are then fixed to 61 by screws and true negative castings 72 formed thereon in the same manner, the metal 72 being separated from 67 by adhesive tape 71. The face 73 corresponds to the line 32<SP>1</SP> to which the stamping is to be trimmed. Transverse strips 77, Fig. 10, or paper or tape are then secured to the part 38 of the model, made to follow the contour 33, 34, 32 and cut or marked at the trim line 32' of the finished stamping. The strips are then bent out of the way and the contour of the model is rounded and extended to correspond to the shape of the initial stamping by pieces 80 ... 83, Fig. 11, the strips 77 are bent to follow the new contour and a first trim line 52 is formed at or just beyond the cut ends 79 or marks. The marginal members 68 are then replaced by marginal base members 85, Fig. 12, corresponding to the contour 80 ... 83 and true negative castings 86 thereof are formed. The end 87 may then be cut to correspond exactly with the line 52. For a small marginal member the base part may be omitted and the whole part be cast in a mould. Holes 98, Fig. 16, may be drilled in the gauge with cast-in bushes 99 if desired for use in drilling holes 100 &c.,. in all the succesive dies 101 1 of - a set. These holes are used for registering pins 102, Fig. 16, which may in some cases also pass through corresponding gauge holes 49, Fig. 2, in sample stampings, or 91, Fig. 13, in a template 89, with holes 90 and slots 93 for marking trim lines for the window opening 31 on the die. To form a gauge hole 49 in correct position, a plug with a central and slightly projecting centre punch, is screwed at 104, Fig. 17, into the hole 100 in the .final forming die 101, after the sample stamping has been brought to final form, and the dies are again closed on the stamping, causing the punch to form a recess in said stamping to guide an annular cutter. A gauge, for a roof or other part so shaped that a unitary gauge could not be removed from the model, is made with parts 119, 121, Fig. 20, formed separately and, if desired, interchangable with parts corresponding to the initial forming die. If the initial and final dies 130, 137, Figs. 24, 25, act in different directions on the stamping, the gauge 127 with the marginal gauge 128 is applied to the initial die 130 in one direction and, with marginal gauge 129, to the final die 137 in another direction. For this purpose the gauge is carried by beams 132 and braces 133 from a pneumatic or hydraulic hoist 131 for the first application and by additional braces 140, Fig. 25, for the second. The hoist is carried by rolls 142 on a rail 141 which may itself be movable. Gauges, for stampings intended to fit together, are fitted together to ensure their co-operation. In a modification the base form is built up by welding section-bars &c. which are perforated or are faced with expanded metal so as to key the cast metal face. In another modification a trim line 113, Fig. 19, on the model 110 is transferred to a negative 111 of a die for stamping an intermediate form by means of strips 116, similar to the strips 77, which are applied to the assembled model and negative successively.