Grinding Wheel-Definition, Material, Grit, Grades, Structure, Types, Specification or Nomenclature, PDF

Before going in details about Grinding Wheel let’s have an overview on Grinding Machine.

Grinding Machine:

Definition:

A grinding machine or grinder is an industrial power tool that uses an abrasive wheel for cutting or removing the material. It can also be defined as a process of metal cutting by using a rotating abrasive wheel from the surface of the workpiece. Generally, the grinding is a finishing operation to show the high surface quality, accuracy of the shape and dimension. Grinding machine operation is also carried out for machining hard material.

Types:

1. Rough Grinders

• Floor or bench grinders
• Portable grinders
• Abrasive belt grinders
• SwingFrame grinders

2. Precision Grinders:

• Surface Grinders
• Cylindrical Grinders-(Plain, Universal, and Centerless)
• Tool and Cutter Grinders
• Internal Grinders-(Chucking, Planetary, and Centerless)
• Special Grinding machine

There are several grinding machine types, each with a different purpose. Here’s a look at some of the most common types of precision grinding machines

Surface Grinders:

A surface grinder consists of an abrasive wheel, a chuck (a workpiece holding device), and a rotary table. The chuck is used to hold the material in place while the wheel and object are rotated to produce a smooth finish.

Cylindrical Grinders:

A cylindrical grinder is used for shaping the outside of a workpiece. These machines accept workpieces in a variety of shapes as long as they can be rotated through a central axis. In a cylindrical grinder, both the workpiece and grinding wheel are simultaneously rotated. Outside diameter grinders, internal diameter grinders, and centerless grinders are all types of cylindrical grinders.

Centerless Grinders:

A centerless grinder is a type of cylindrical grinder which uses two rotary wheels to secure the workpiece in place. Unlike a centered grinder, a centerless grinder does not make use of a spindle. The speed of the rotation of the wheels determines at what rate the material is removed.

Tool & Cutter Grinders:

A tool and cutter grinder makes use of a CNC machine tool with up to 5 axes and multiple grinding wheels. These devices are used for sharpening and producing milling cutters such as drills, endmills, and step tools. It is also widely used for producing the tools needed in the woodworking and metal cutting industries.

Plain Cylindrical Grinding Machine:

Following are the main working parts of Plain Cylindrical Grinding Machine:

Base or Bed:

It is a cast-iron bed resting on the floor and supports the other parts which are mounted on it. The base houses the table drive mechanism and on the top of the base accurately machined guideways are provided at right angles for the table to slide on it.

Tables:

There are two tables, lower table, and the upper table. The lower table provides transverse movement to the work by sliding over the guideways on the bed, which can be moved by hand or power. The upper table is pivoted at its center over the sliding table and is provided with a headstock and a tailstock. These can be positioned anywhere along the table to hold the workpiece. The upper table can be swiveled and clamped for grinding straight or tapered surface.

Head Stock:

The headstock is fixed over the bed and supports the workpiece by means of a dead center and drives it by means of dog or it may hold the workpiece in a chuck and drive it.

Tailstock:

The tailstock can be adjusted and fixed in any required position to accommodate different lengths of the workpiece.

Wheel Head:

It consists of a grinding wheel and its driving motor. The wheel head is mounted on a slide at the rear end of the base and moves perpendicularly to the table ways by hand or power to feed the grinding wheel for the work.

Crossfeed:

The grinding wheel can be fed to the work by engagement of the crossfeed control lever by hand or power.

Operations:

A grinding machine is a machine tool used for producing very fine finishes or making very light cuts, using an abrasive wheel as the cutting device. Typical categories of grinding machine include:

• Surface grinding
• Cylindrical grinding
• Internal grinding
• Center grinding
• Centerless grinding

To learn more in detail check out : Grinding Machine

Grinding Wheel:

Definition:

A Grinding wheel has multiple cutting edges made up of many hard particles called as Abrasive. These abrasive are crushed to have sharp edges for cutting operation. The Abrasive grains are properly mixed with a suitable bond which acts as a holder when the wheel is in use.

Grits or Grain:

The grit or grain is used to indicate a general size of abrasive for making a grinding wheel. Grits or Grain size is denoted by a number that indicates the number of meshes per linear inch of the screen through which the grain pass when they are graded after crushing. Generally, the coarse wheel is used for fast removal of the material and Finely graded wheel should be used to grind Hard and Brittle materials. 

The different Grits or Grain of the grinding wheel are as follows:

Grade:

The grade refers to the harness or strength with which the bond holds the abrasive grains of a grinding wheel in a place. The Grade is indicated by the English alphabet A to Z. A denotes Softest and Z denotes Hardest Grade.

The different grade of the grinding wheel are as follows:

Structure:

The structure refers to the spacing between the abrasive grains in the grinding wheel. It is denoted by the number of cutting edges per unit area of wheel face and size of void spaces between grains. If there is a large number of cutting edges per unit area, the structure is called Dense structure otherwise it is called an open structure.

The different structure of the grinding wheel are as follows:

Types:

The Grinding wheels are available in different shapes and sizes to suit with the different machine operations.

Following are the types of Grinding wheels:

1. Straight side grinding Wheels

• Straight Disc wheel
• Straight both side recessed
• Straight one side recessed
• Straight cup wheel

2. Cylindrical Wheel 
3. Tapered wheel
4. Saucer wheel
5. Segmented wheel
6. Dish wheel
7. Flaring cup wheel
8. Mounted point wheel

1. Straight side grinding Wheels:

These are used for the cylindrical, center-less, and surface grinding operation.

2. Cylindrical Wheel:

Used for producing a flat surface.

3. Tapered wheel:

Used for grinding thread, gear teeth, etc

4. Saucer wheel:

Used for sharpening of circular and band saws.

5. Segmented wheel:

Used for the vertical spindle, rotary, and reciprocating table surface grinders.

6. Dish wheel:

This is used for tool room work.

7. Flaring cup wheel:

This is used for tool and cutter grinding.

8. Mounted point wheel:

These are used for grinding the special contours and Sharpening saws.

Specification or Nomenclature:

The Indian standard marking system ( IS: SS1-1954 ) has been used to indicate the various characteristics of a grinding wheel.

Each marking consists of 6 symbols, denoting the following characteristics:

1. Abrasive 

2. Grain Size

3. Grade 

4. Structure

5. Bond type

6. Manufactures record

W     A     30     I     4     V     17

Here, 

W (Prefix) = Manufacture abrasive type symbols.

A (Abrasive) = [ A = Aluminium Oxide ], [ C = Silicon Carbide ], [ D = Diamond ]

30 (Grain Size) = 4 Types of grain Size.

1. Coarse= 10,12,14,16,20,24
2. Medium=30,36,46,54,60
3. Fine=80,100,120,150,180
4. Very fine=220,240,280,320,400,500,600

I (Grade) = Grade categories in to 3 parts.

1. Soft= A,B,C,D,E,F,G,H
2. Medium=I,J,K,L,M,N,O,P
3. Hard=Q,R,S,T,U,V,W,X,Y,Z

4 (Structure) =  Structure categories in 2 parts.

1. Dense= 1,2,3,4,5,6,7,8
2. Open= 9,10,11,12,13,14,15

V (Bond Type) = Vertified Bond

1. V= vertified
2. B= Resionid
3. R= Rubber
4. E= Shellac
5. S= Silicon
6. O= Oxychloride  

17 (Suffix) = Manufacturing abrasive type symbol

Application:

The main application of grinding wheel is to remove the material in the form of tiny chips and make the surafce smooth as much as possible. The Grinding machine is a surface finishing Machine in which Grinding wheels are fixed for surface finish.