The choice of the lap material should be determined by the material and properties of the valve abrasive. The lap material should have: fine and uniform microstructure, good sand-embedding performance, good wear resistance, sufficient rigidity, no deformation, and its hardness is softer than that of the abrasive parts. The materials used for the laps under normal conditions are as follows.
Aluminum: The aluminum texture is softer than copper and is suitable for fine grinding of soft metals such as copper.
Lead, babbitt: Suitable for polishing and grinding soft steel or other soft materials.
Glass: The glass texture is hard and brittle, suitable for the grinding and polishing of workpieces, especially the hardening of hardened steel.
Low carbon steel: The toughness of low carbon steel is larger than that of cast iron. It can adapt to the workpieces such as slender round holes, tapered holes and threads that are hard to be polished by cast iron. Low carbon steel is generally used as rough material.
Copper: The copper has high toughness and good wear resistance. It is suitable for the rough grinding valve of the work with low margin and large roughness requirement. It can function as a low carbon steel lap (but the cost is high, and it is rarely used).
In order to save material and reduce the lap, the lap is often used for both application of abrasives and sanding or sandpaper. A lapper specially designed to support abrasive cloth or sandpaper, generally made of carbon steel or cast iron.
Asphalt: The asphalt is soft and suitable for grinding and polishing marine valves such as glass and crystal. It is also suitable for the finishing of hardened steel. Asphalt has a strong adaptability to the shape of the workpiece. Leather, felt, polyester fabric: Soft texture, often used to polish workpieces. The polyester fabric is even and even, and the liner is on a flat lap, and the effect of lapping and polishing is good.
Cast iron: Cast iron contains flake graphite, which has good wear resistance and lubricity, and high strength. It also has the advantages of low cost and easy processing. Therefore, cast iron laps are suitable for grinding workpieces of various materials such as cemented carbide, hardened steel, non-ferrous metals, etc., and are also suitable for sanding, sanding and sanding. The materials used for cast iron are gray cast iron and ductile iron, and the hardness is generally HB 120-220. Cast iron laps guarantee quality, while grinding is efficient and widely used.