| abstract |
The invention relates to a pressing method for a powder metallurgy part hole with a small middle and two large ends. By making full use of retarded elasticity and elastic deformation of powder metallurgy products after forming and demoulding, a back taper hole is directly formed by a mandrel without investment of a re-pressing mould, production procedures are decreased, production cycle is shortened, and the qualification rate of the products is increased, so that manufacturing cost is greatly reduced. |