Skip to main content

ABRASIVES

ABRASIVES

An abrasive is a material, often a mineral that is used to shape or finish a work piece through rubbing which leads to part of the work piece being worn away. While finishing a material often means polishing it to gain a smooth, reflective surface which can also involve roughening as in satin, matte or beaded finishes. Abrasives are extremely commonplace and are used very extensively in a wide variety of industrial, domestic, and technological applications. This gives rise to a large variation in the physical and chemical composition of abrasives as well as the shape of the abrasive. Common uses for abrasives include grinding, polishing, buffing, honing, cutting, drilling, sharpening, lapping, and sanding. 

1.     Grit or grain:
It indicates the size of the abrasive grains used in making a wheel.
·        Coarse wheels are used for fast removal of materials and for soft and ductile materials.
·        Fine grain wheels are used to grind hard and materials.
2.     Grade: 
It refers to the tenacity or hardness with which the bind held the cutting points.  It is denoted by the 'A' -softest and 'Z'-the hardest hard wheels are recommended for soft   materials and soft wheels are recommended for the hard materials.

3.     Structure or grain spacing:
The structure refers to the number of cutting edges per unit area of wheel face as well as to the number and size of void spaces between grains & denoted by numbers. Soft, tough and ductile materials and heavy cuts require an open structure where as hard and brittle materials and finishing cuts require a dense structure.



Labels:

Comments

Post a Comment

Popular posts from this blog

DOM MANUAL / B-TECH / MECHANICAL / KUK - TO FIND THE SPEED AND TORQUE OF DIFFERENT GEARS IN AN EPICYCLIC GEAR TRAIN.

OBJECTIVE: TO FIND THE SPEED AND TORQUE OF DIFFERENT GEARS IN AN EPICYCLIC GEAR TRAIN. SPECIFICATIONS : 1.       GEAR TRAIN : SUN GEAR : 14 TEETH 2.       PLANT GEAR: 21 TEETH (2 NOS.) 3.       INTERNAL GEAR WITH : 56 TEETH TORQUE MEASUREMENT ·          INPUT TORQUE – MOTOR CURRENT CALIBRATED FOR MOTOR TORQUE. ·          PLANT CARRIER - PULLEY OF 50 MM DIA AND SPRING BALANCE. ·          INTERNAL GEAR - PULLEY, 120 MM DIA AND SPRING BALANCES. Ø   BOTH PULLEYS ARE PROVIDED WITH ROPE OF 12 Ø   MM DIA Ø   DRIVE MOTOR - 1HP DC MOTOR RPM MOTOR OPERATING ON 220 VOLTS Ø   50 HZ SUPLLY, DRIVING THE SUN GEAR. CURRENT(AMPS) TORQUE 1.00 0.5 1.20 1.5 1.40 2.5 ...
359 comments
Read more

MANUFACTURING PROCESS - DRAFT OR TAPER ALLOWANCE

DRAFT OR TAPER ALLOWANCE BY DRAFT IS MEANT THE TAPER PROVIDED BY THE PATTERN MAKER ON ALL VERTICAL SURFACES OF THE PATTERN SO THAT IT CAN BE REMOVED FROM THE SAND WITHOUT TEARING AWAY THE SIDES OF THE SAND MOLD AND WITHOUT EXCESSIVE RAPPING BY THE MOLDER. FIGURE  SHOWS A PATTERN HAVING NO DRAFT ALLOWANCE BEING REMOVED FROM THE PATTERN. IN THIS CASE, TILL THE PATTERN IS COMPLETELY LIFTED OUT, ITS SIDES WILL REMAIN IN CONTACT WITH THE WALLS OF THE MOLD, THUS TENDING TO BREAK IT.  FIGURE  IS AN ILLUSTRATION OF A PATTERN HAVING PROPER DRAFT ALLOWANCE. HERE, THE MOMENT THE PATTERN LIFTING COMMENCES, ALL OF ITS SURFACES ARE WELL AWAY FROM THE SAND SURFACE. THUS THE PATTERN CAN BE REMOVED WITHOUT DAMAGING THE MOLD CAVITY.  PATTERN HAVING DRAFT ON VERTICAL EDGES DRAFT ALLOWANCE VARIES WITH THE COMPLEXITY OF THE SAND JOB. BUT IN GENERAL INNER DETAILS OF THE PATTERN REQUIRE HIGHER DRAFT THAN OUTER SURFACES. THE AMOUNT OF DRAFT DEPENDS UPON THE LENGTH OF THE...
2 comments
Read more

ELECTROCHEMICAL MACHINING (ECM)

ELECTROCHEMICAL MACHINING (ECM) INTRODUCTION:- Electro chemical machining (ECM) is a method of removing metal by an electrochemical process. It is normally used for mass production and is used for working extremely hard materials or materials that are difficult to machine using conventional methods. Its use is limited to electrically conductive materials; however, this includes all metals. ECM can cut small or odd-shaped angles, intricate contours or cavities in extremely hard steel and exotic metals such as titanium, carbide etc. ECM is often characterized as "reverse electroplating," and is similar in concept to electrical discharge machining in that a high current is passed between an electrode and the part, through an electrolyte material removal process having a negatively charged electrode (cathode), a conductive fluid (electrolyte), and a conductive work piece (anode); however, in ECM there is no tool wear. The ECM cutting tool is guided along the desired ...
53 comments
Read more