GB544782A - Method of and apparatus for forming twist drills and helical shapes - Google Patents

Abstract

544,782. Making twist drills &c. HURSCH. MAN, A. Oct. 25, 1940, No. 15697. [Classes 83 (ii) and 83 (iv)] Forging dies.-In an apparatus for forming twist drills or other helical shapes, the work is forged between upper and lower die blocks 1, having die bars extending angularly across each semicylindrical channel each die bar having a smaller sectional area at the initial contacting end than at its finishing end. The channels 3 of the upper and lower die blocks at the receiving end (top of Fig. 1) are of true cylindrical form at the centre part 4 with slight relief at the sides 5 and 6. Within each channel is located an unsymmetrical die bar 7 which may either be integral with the die block, Fig. 1, or formed on an insertable separate member 8, Fig. 13, which is located above a knock out opening 10. With the latter construction variations in pitch and size of flute may be provided for by using different inserts. The drills formed have elevated land portions 12 and clearance land areas 13 intermediate the flutes 14, 15. Different finished sizes may be produced from the same dies by varying the degree of grinding or machining of the portions 12. The clearance lands are formed by parts 21 of the dies of uniform height. The part elliptical shape produced by the relieved parts 5, 6 at the entering end are reduced to true cylindrical shape by the parts 21, the work tending to feed itself forward automatically. The centre section of the die bar is almost symmetrical, Fig. 7. The clearance forming section then gradually widens and the extension land enters the free space 27.