What is honing?
Honing generally refers to the whetstone inlaid on the honing head, also known as the honing stick, which is the finishing process of the finishing surface.
Honing is mainly used to process various cylindrical holes with a diameter of 5 to 500 mm or more, such as cylinder barrels, valve holes, connecting rod holes and box holes, etc. The ratio of hole depth to diameter can reach 10 or even larger.
Under certain conditions, honing can also process external circles, planes, spherical surfaces and tooth surfaces.
The periphery of the honing head is inlaid with 2 to 10 whetstones with a length of about 1/3 to 3/4 of the hole length. When honing the hole, it both rotates and moves back and forth, and at the same time, it expands evenly through the spring or hydraulic control in the honing head. Therefore, the contact area with the hole surface is large, and the processing efficiency is high. The dimensional accuracy of the hole after honing is IT7~4, and the surface roughness can reach Ra0.32~0.04 microns.
A honing machine is generally used for honing, and the main shaft of the machine tool and the honing head are generally floating connection; but in order to improve the ability to correct the geometry of the workpiece, a rigid connection can also be used.
When honing a hole, the outer periphery of the honing head is generally inlaid with 2 to 10 whetstones, which are driven by the machine tool spindle to rotate in the hole, and at the same time perform linear reciprocating motion. At the same time, the uniform outward expansion of the whetstone is controlled by the spring or hydraulic pressure in the honing head, and the machined hole wall is fed radially.
The size of the honing allowance depends on the hole diameter and workpiece material, generally 0.02 to 0.15 mm for cast iron and 0.01 to 0.05 mm for steel. The speed of the honing head is generally 100-200 rpm, and the speed of the reciprocating motion is generally 15-20 m/min. In order to flush away chips and abrasive particles, improve surface roughness and reduce the temperature of the cutting zone, a large amount of cutting fluid, such as kerosene or a small amount of spindle oil, is often used during operation, and sometimes extreme pressure emulsion is used.
The characteristics of the honing process are:
1. Honing processing is an efficient processing method to achieve high precision, high surface quality, and long life of the workpiece surface. It can effectively improve the dimensional accuracy, and shape accuracy, and reduce the Ra value, but cannot improve the positional accuracy of holes and other surfaces.
2. It can process cast iron parts, hardened and unhardened steel parts, bronze parts, etc., but it is not suitable to process non-ferrous metal parts with high toughness.
3. Honing is mainly used for hole machining. In hole honing, it is guided by the center of the original machined hole. The machining aperture range is φ5～φ500, and the aspect ratio can reach 10.
4. Honing is widely used to process cylinder holes, cylinder barrels, valve holes, and various gun barrels in mass production. It can also be used in single-piece and small-batch production.
5. Concentricity cannot be determined during honing.
6. Compared with grinding, honing has the characteristics of reducing manual labor, high productivity, and easy automation.
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---EDITOR: Elio Song
---POST: Cynthia Lee