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Sunday, 24 November 2013

Bonds

Bonds Points : Bonds, Vitrified Bond, Silicate Bond, Shellac Bond, Rubber Bond, Resinoid Bond Definition Bond is the material in a grinding wheel that holds the abrasive grain particles in the form of a wheel. As the grains get dull, pressure on the wheel causes the bond to break down and release the dull grains. Thus exposing new sharp grains. The bond holds the individual grain in much the same manner as a tool. holder holds a tool bit. Five principal bond types used in the manufacture of grinding wheels are: 1. Vitrified Bond The vitrified bond is used in about 75% of all grinding wheels. The reason for this is the fact that it forms a very uniform wheel which is not affected by .oils, acids, water, heat or cold. Wheels of this bond can be made dense or porous, and in considerable less time than other kinds. These wheels are free from hard and soft spots. The recommended speed for these wheels is 1677 MPM or 5500 FPM with a maximum speed of 1982 MPM or6500FPM. 2. Silicate Bond In this bond, Silicate soda is used. Silicate wheels are milder acting than those made by other processes, and wear away more rapidly. They are suitable for grinding edged tools (such as drills, reamers, milling cutters etc.) where the heat must le kept to a minimum. Silicate wheels can be made in larger diameters than vitrified wheels since they have little tendency to crack or wrap in the baking process. The hardness of the wheel is controlled by the amount of silicate of soda used, and the amount of taming given the material in the mold. 3. Shellac Bond Shellac-bonded wheels are used for grinding job which required a huffed or high polish or burnished surface, such as mill rolls, camshafts and cutlery. Other uses are sharpening large saws, cutting off operations and finishing large rolls. This bond is adapted to thin wheels as it is very strong and has some elasticity. 4. Rubber Bond Rubber bonded wheels are used for grinding mill rolls and bearings where a high luster finish is required. Very thin wheels can be made by this bond because of the elasticity of the material. Wheels of this bond are used for high speed grinding operations and because of their high safety factor, can be made very thin and makes them ideal for cutting off purposes when coolant is used. 5. Resinoid Bond Resinoid bonded wheels are specially suit d for heavy duty grinding such as snagging, castings, steel billets, and so forth, and for cutting-off stock. When used for snagging purposes they may be operated as fast as 2896meter per minute or 9500 surface feet per minute. When installed in proper equipment they. may be run as fast as 4878 MPM or 16,000 SFPM for cutting-off operations. Resinoid bonded wheels can be made in various structures from hard, dense, coarse wheels to soft, open, fine wheels.

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