Last Updated on March 9, 2023 by Ali Abbas Khan
In this new article, we shall study the Definition, Parts or Construction, Working Principle, Advantages, Disadvantages, and Application of Honing Process in detail. We have also provided a PDF download link of the same at the very end.
Table of Contents
the History of the Honing Process
It was in the 16th century when Leonardo da Vinci first used a tool to smoothen the internal walls of a wooden pipe with the help of a stick attached to an Abrasive paper on it. This stick could move in linear as well as radial directions. Honing tools were developed in the early 20th century to hone the internal components of internal combustion engines. In 1924 the first five-bladed honing tool with a stick and spring attachment was designed and patented. After a few years, the honing process was used for production purposes in industries.
What is a Honing Process?
Honing is an abrasive machining process that is a combination of grinding and drilling processes. A honing process uses an Abrasive grinding tool to accurately machine the given workpiece. A honing process improves the surface quality of the workpiece as well as provides dimensional accuracy to the part being machined.
A moving Abrasive stone is made to come in contact with the part to be machined hence producing an accurate finished job. Honing is used in industries where accuracy and aesthetics both are considered important. Generally, a honing process uses CNC to direct the tool on the workpiece. A honing process is mostly used to finish the boreholes in a workpiece.
Characteristics of Honing Process
The following are the characteristics of Honing Process
- It is a low-velocity, highly accurate process.
- The honing process generates a cross-marked surface on the workpiece. This workpiece is used to hold lubricants.
- It can be used for correcting the roundness of the hole.
- High tolerance of 2 to 3 microns can be achieved.
- Both hard and soft materials can be honed.
- The range of cutting speed varies from 0.25 to 1m/s.
- The cutting angle ranges from 60 to 90o.
- The pressure applied on the lateral surface area of the workpiece during the honing process ranges from 1000kPa to 2500kPa.
Working Principle of Honing Process
The basic principle involved in the honing process is the cutting action performed by the Abrasive particles when a linear, as well as a tangential force, is applied. The friction generated by the contact of Abrasive stones and the workpiece results in the material removal from the workpiece.
The following are the steps as to how Honing Process is performed
- The workpiece to be honed is mounted on the worktable and is clamped with the help of fixtures. A required honing tool is attached to the spindle and the stability of the tool is checked.
- The operator selects different parameters such as feed and speed of the tool. When the tool enters the hole it expands due to the tapered cross-section of the cone inside the tool.
- Forces act perpendicular and parallel to the lateral surface area of the hole. These forces result in the cutting action due to the Abrasive stones and provide a great surface finish.
- Coolant is added if required during the process to prevent overheating of the surface. Once the honing process is done the tool is removed from the hole and the stones are pulled inwards due to the spring-back force.
- The job is then allowed to cool and then it is removed by loosening the fixtures.
Honing Machine Types
There are two types of honing machines which are as follows
- Vertical Honing machine
- Horizontal Honing machine
The construction of the honing machine is very similar to drilling machines. Besides this, a Honing tool can also be mounted on a lathe machine or a Drilling machine. The only requirement of the honing process is that the tool should rotate as well as move parallel to the axis of the hole.
Vertical Honing Machine Construction or Parts
The column and the elevated screw are fitted on the cast iron base. The column connects CNC to the motor and also contains supporting elements. The elevated screw is connected to the work table and fixtures are stuck to the work table. One end of the spindle is connected to the motor and the other end is connected to the tool through a support element. The construction is much similar to a drilling machine.
- Base: The base is the supporting element that is used to rigidly hold the whole setup of honing equipment. The base is made of cast iron to absorb maximum vibrations and provide stability to the equipment.
- Column: The column is the main supporting element used in the setup. A vertical column is used to hold the motors, spindle, tool, and workpiece. It also acts as a connecting element for various working parts.
- Guideways: The guideways are used for the vertical movement of the workpiece.
- Worktable: A worktable is used to hold fixtures on it. It can be movable or rigid.
- Fixtures: Fixtures are the clamping devices used to clamp the workpiece. In the case of the honing process, the fixtures must be strong and rigid to fulfill the accuracy requirements of the honing process.
- Spindle: A spindle is a connecting device that is used to connect the tool with the motor for providing a rotational motion to the tool.
- Support: A support element is used to support the spindle and prevent it from breaking.
- Elevated screw: The elevated screw is provided to increase the height of the worktable.
- CNC: A computer numerical controller is used to control the motion of the tool concerning the workpiece or to control the movement of the workpiece concerning the tool.
- Power supply: A DC power supply is used in the case of the honing process.
- Honing tool: The Tool is the most important part of the honing process. A honing tool makes the honing process different from the grinding and drilling processes. The Tools used in vertical and horizontal honing machines are similar and are described further.
Horizontal Honing Machine Construction or Parts
The construction of a horizontal honing machine is very simple. The base acts as a platform for all the elements or components to be mounted. The tailstock is mounted on one end and the Headstock on the other end. The worktable is attached in between the Tailstock and Headstock. The worktable is allowed to move in the horizontal plane. The spindle is attached to the Headstock and the tool. It is used to transfer the motion of the motor to the tool. Fixtures are located on the worktable to clamp the workpiece.
- Headstock: A Headstock contains a motor gear arrangement to vary the speed of rotation of the tool.
- Bed: A bed is similar to the base in a vertical honing machine. It is made of cast iron and works as a damper.
- Spindle: The spindle is the connecting element that connects the motor and the tool.
- Column: The column is a supporting element used to support the Headstock.
- Fixtures: Fixtures are used to clamp the workpiece and restrict the degrees of freedom. The fixtures in the case of horizontal honing must be very accurate as a larger amount of force is exerted on the workpiece.
- CNC: A computer numerical controller must be installed in case of horizontal honing to ensure better accuracy. This may eliminate maximum human errors.
- Honing tool: The honing tool is the most important element which is explained below.
- Tailstock: The tailstock is that element that is situated at the other end of the base. It is used for giving support to the workpiece.
There are varieties of honing tools available in the market which can be used for different purposes. The given diagram shows a double-cone honing tool. This consists of an Abrasive stone on the outer diameter of the tool. The stone is that part that comes in contact with the workpiece. There are two cones situated inside the stone carrier. As soon as a linear force is applied to the shaft the stones are pushed outwards. This happens due to the tapered cross-section of the cone. The stones are pulled back by the reverse action of the springs.
Abrasive Particles used
Abrasive stones are Abrasive particles bound together to form a solid structure that can produce friction while rubbing against another material. There are a variety of Abrasive particles available based on grain size, desired surface finish, and various other factors. The most commonly used Abrasive particles are aluminum oxide, silicon carbide, and tungsten carbide.
An important Parameter of the Honing Process:
The honing operation highly depends on the Abrasive particles used. The choice of Abrasive depends on the hardness of the workpiece and the surface finish desired. For very hard workpieces diamond is used as a tool.
The spindle speed or RPM of the tool is an important parameter that decides the different features of the workpiece. For example, if high material removal is the key concern the speed should be minimum. If surface finish is the key concern the speed should be high.
The reciprocating speed of the tool w.r.t to the workpiece affects the surface finish of the job. Higher reciprocating speeds result in the poor surface finish of the job.
As mentioned above the honing pressure ranges from 1000kPa to 2500kPa. Lower honing pressure results in low material removal and higher pressure results in poor surface finish.
Advantages of Honing Process
- Accuracy: The honing process is highly accurate and precise. In industries where a hole or bore diameter must be accurate, the honing process is of great advantage.
- The hardness of the workpiece: Another advantage of the honing process is that it can machine any material regardless of its hardness and molecular structure.
- Maintains the centerline: Honing process maintains the centerline of the bore or a hole. Other finishing processes may disturb the centerline of the hole.
- Material removal: Less material is removed and finishing is obtained with the help of a honing process. This is due to the use of an Abrasive tool.
- The pattern generated: Honing process generates a cross-marked pattern on the surface of the workpiece. This provides a great advantage for the workpiece to hold lubricants.
Disadvantages of Honing Process
- High initial cost: The initial cost of the equipment is high. This is an economical drawback of the honing machine.
- High tool wear: Abrasive stones are used as the main cutting edge. The roughness of Abrasive stones gets decreased easily in the case of the honing process.
- Straightness of the hole: The honing process only improves the inner surface quality of a hole or a bore. It does not improve the straightness of the hole.
- Types of materials: Honing process is suitable only for ferrous materials, it is not very effective on nonferrous materials.
Applications of Honing process
- It can be used for finishing automobile crankshafts
- Honing process is used for finishing gears in the automobile industry.
- It is also used for production purposes where hollow cylindrical bores must be accurately finished.
- It is also used for finishing the internal diameter of the IC engines.
- It can be used for improving hole roundness.