The Impression Block used in fishing operations is an assembly of a steel body and a soft lead founded at the bottom. Milling Shoe can be divided into threekindsflat-bottomor concave-bottommilling shoe, guide milling shoeand cone milling shoe, according to its structure and shape. At themilling surface, the carbide particles are built up by welding, whichplays a part of self-milling. It is used ...