Honing is a grain-incorporated cutting process used to improve the shape, dimensional accuracy, and surface quality of a workpiece while maintaining constant surface contact with the tool. Honing is performed after precision machining such as grinding.
What Is Honing Machining?
Grinding is a low-speed grinding process. Since the material is removed at a slower rate than normal grinding speed, pressure and heat generation are minimized, so size, surface roughness, and microstructure can be well controlled. Since the workpiece is floating and not supported by any formwork, it will not deform. While honing can produce a very smooth finish, the surface will have a cross-grained appearance.
The general honing process is to rotate and reciprocate the honing of the stone, pressurize the inner surface of the hole, and apply a large amount of grinding fluid according to the surface contact. During the honing process, one or more rod-shaped stones are used to assemble the mandrel body, and the stones are pushed back and forth with wedges to expand the stones, and the holes and workpieces inside are ground into a rectangular cross-section. Machined to achieve the desired precision and surface finish. The finished surface will form a unique CROSS HATCH that easily forms an oil film. Therefore, when sliding with other parts, it will be smoother, which is the characteristic of honing, creating a superior sliding surface.
The Processing Principle of the Honing Process:
The processing method of honing is to drive the honing tool (honing head) through the main shaft of the machine tool, and make a straight up and down reciprocating motion while rotating. Under the action of a certain outward bulging pressure, the whetstone (grinding rod) on the honing head removes the wear debris on the surface of the workpiece and grinds out spiral cross meshing wear marks. Whetstone is a strip-shaped abrasive tool composed of abrasives and binders. According to the different materials to be processed, the abrasives in the corresponding whetstone can be selected from the aspects of shape, type, particle size, binder, hardness, structure, and performance. The honing head usually consists of multiple whetstones, which can machine parts with multiple holes at the same time.
Polishing is used to improve the hole precision after boring, drilling, and internal grinding. A honing tool is a group of strip-shaped abrasives composed of aluminum oxides or carbon-silicon compounds, commonly known as Whetstone. The whetstone is embedded on the rotating mandrel and rotates at a speed of 45~90 m/min to generate radial force. The tool reciprocates in the axial direction, producing parallel and intersecting lines on the surface of the hole, and the whetstone on the mandrel can be adjusted according to different diameters.
The Purpose of Honing Processing:
Honing can completely polish the inner diameter of a workpiece with a small number of grinding cuts. Honing can improve machining accuracy. The honing time is short, the life is long, the surface roughness is stable, and the workpiece has no scratches. Both soft and hard materials have corresponding specifications and various adhesives to correspond to different applications. Polishing is used for the processing of precision holes, such as engine cylinder holes, compressor cylinder holes, connecting rods, pump bodies, and control blocks.
The degree of surface finish of honing can be controlled by the size, pressure, and speed of the abrasive used. Cutting fluid is used to remove chips and reduce temperature. Without proper treatment, honing can produce holes that are neither straight nor round, as well as machining defects such as bell mouth, corrugation, barrel shape, slope, etc.
What Are the Characteristics of Honing Processing?
In addition to improving the surface quality of machining accuracy, roundness, cylindricity, and shape accuracy, honing is beneficial to the formation and maintenance of oil film due to the intersecting lines on the surface of the workpiece. Therefore, the service life of the workpiece to be processed is often higher than that of the workpiece processed by other processing methods, and it is especially suitable for the processing of precision couplings that require relatively high relative motion. The honing processing range is wider, in addition to processing through holes, discontinuous holes, blind holes, multi-level holes, and cycloid holes, it can also process plane, spherical, and tooth surfaces, which can be adapted to the processing of various metal materials.
Is There a Difference Between Honing and Grinding?
The difference between honing and grinding is that the honing technique uses a grindstone to grind the workpiece at a lower speed, whereas grinding uses the impact of a grindstone to grind at a very high speed. Cut the workpiece surface. Therefore, the workpiece surface with inner diameter grinding is prone to instantaneous high temperature under high cutting pressure, resulting in changes in mechanical and physical properties, thereby damaging the workpiece surface and generating internal stress.