Made By: sikander pal 08625g

mechanical engineering

LAPPINGLAPPING OPERATIONOPERATION

Lapping is a machining operation, in which two surfaces are rubbed together with an abrasive between them, by hand movement or by way of a machine.

Lapping can take two forms. The first type of lapping (traditionally called

grinding), typically involves rubbing a brittle material such as glass against a surface such as iron or glass itself with an abrasive such as aluminum oxide, jeweller's rouge, optician's rouge, emery, silicon carbide, diamond, etc., in between them.

The other form of lapping involves a softer material such as pitch or a ceramic for the lap, which is "charged" with the abrasive. The lap is then used to cut a harder material—the workpiece. The abrasive embeds within the softer material which holds it and permits it to score across and cut the harder material.

Lapping has four main Lapping has four main purposes:purposes:

• to obtain greater accuracy as to dimensions• to improve imperfections of shape• to obtain a smoother polished surface• to improve the fit between surfaces.

LAPSLAPS Laps are usually made of soft cast iron, copper, brass, lead or

ceramic. In general, soft close-grained iron is the best material to use for a higher degree of accuracy in the finished product.

External laps are commonly made in the form of an outer ring or holder and an inner shell.

This inner shell is made of cast iron, copper, brass or lead. Ordinarily, the lap is split and screws are provided for adjustment. The length of an external lap should be equal to the diameter of the work or longer. Large ring laps usually have a handle for moving them across the work. Laps for producing plane surfaces are made of cast iron. In order to secure accurate results the lapping surface must be a true plane.

• A flat lap that is used for roughing or blocking down will cut better if the surface is scored by narrow grooves. They are usually located about 1/2 inch apart and extend both lengthwise and crosswise thus forming a series of squares similar to those of a checkerboard. For fine work a lap having an unscored surface is used and the lap is charged with fine abrasive.

Lap-O-Valve1200900500320220Cleaner/Degreaser

GarnetGK10GK7GK5

White Aluminum Oxide38-100038-120038-22038-24038-32038-40038-50038-60038-900

WHITE ALUMINUM OXIDEWHITE ALUMINUM OXIDE38-100038-1000

IDENTITY INFORMATION

This product consists of aluminumoxide powder mixed in an oil-soapbase which is comprised of hydrocarbon oils, vegetable oils, and animalfatty acid soap.

Solids content is approximately 30%. Contains lessthan 50 ppm leachable chlorides.

PHYSICAL PROPERTIESSpecific Gravity (H2O = 1)

.9, approximate

Melting Point 110°F

Evaporation Rate (Butyl Acetate = 1)

Negligible

Boiling Point N/A

Solubility in Water No

Vapor Density (AIR = 1)

Greater than air.

Appearance and Color

White paste, slight oily odor.

FIRE AND EXPLOSION FIRE AND EXPLOSION HAZARD DATAHAZARD DATA

Flash Point (Method Used) 375°F, actual test

Flammable LimitsLELUEL

N/AN/A

Extinguishing Method CO2 or foam.Do not use water.

Special Fire Fighting Procedures Treat as oil fire.

Unusual Fire and Explosion Hazards None

REACTIVITY DATAREACTIVITY DATA

Stability Stable

Conditions to Avoid None

Hazardous Polymerization Will not occur.

Conditions to Avoid None

Hazardous Decompositionor Byproducts

None

•Small lapping plate made of Small lapping plate made of cast ironcast iron

a piece of lead may be used as the lap, charged with emery, and used to cut a piece of hardened steel.

That particular plate is made of cast iron. In use, a slurry of emery powder would be spread on the plate and the workpiece simply rubbed against the plate,

Lapping machinesLapping machines• Commercial lapping

machine The lap or lapping plate in this

machine is 30 cm (12") in diameter.

the lap is the large circular disk on the top of the machine. On top of the lap are two rings. The workpiece would be placed inside one of these rings.

A weight would then be placed on top of the workpiece. The weights can also be seen in the picture along with two fiber spacer disks that are just used to even the load.

In operation, the rings stay in one location as the lapping plate rotates beneath them.

In this machine, a small slurry pump is used.

When there is a requirement to lap very small specimens a lapping jig can be used to hold the material while it is lapped .

A jig allows precise control of the orientation of the specimen to the lapping plate and fine adjustment of the load applied to the specimen during the material removal process.

Due to the dimensions of such small samples, traditional loads and weights are too heavy as they would destroy delicate materials.

The jig sits in a cradle on top of the lapping plate and the dial on the front of the jig indicates the amount of material removed from the specimen.

•Removal Rate and Surface Roughness in Removal Rate and Surface Roughness in Lapping of Mn-Zn Ferrite Lapping of Mn-Zn Ferrite

• Sn lapping plate and 0.5 – 2.0 μ diamond abrasives generally used for lapping mn-zn ferrite. •The diamond grains during lapping can be classified into fixed and loose grains.• the pitch size of the grooves on the lapping plate generated by facing operation has a significant effect on the removal rate. • The average removal rate with fixed and loose grains is about 2.7 times higher than that with only fixed grains, and from this result it is known that during lapping, the work material can be removed mainly by loose grains.

Lapping methodsLapping methods•MECHANICAL LAPPING

•WET LAPPING

•DRY LAPPING

MECHANICAL LAPPING: This method includes the addition of a

mechanical means of applying pressure and motion.

The work or parts are carried in a holder of the planetary type that revolves or rotates about the center of the lap.

Mechanical lapping can also be performed with non-rotating laps for certain types of flat lapping: for gage blocks, etc.

Machines of this type have a stationary lower and a removable non-rotating upper lap.

The weight of the upper lap can be adjusted to meet lapping requirements.

Such lapping machines may also use bonded abrasive laps.

WET LAPPING: In wet lapping, the abrasive is mixed into a

carrier or vehicle. This even film of abrasive covers the total lap area.

The carrier acts as a lubricant and absorbs the heat generated by the abrasive against the metal. It allows the abrasive to cut the material by resisting the rolling of the

abrasive granules.

DRY LAPPING: This method is used for the final finishing of

a part. Laps are charged with the proper abrasive and the surface is barely moistened with a very thin oil such as spindle oil, gasoline, naptha, mineral seal oil, etc.

Caution: Kerosene may cause scratches.

Just enough pressure to insure contact is used. If too much pressure is used, or if the lapping operation is too fast in motion, the lap may strip. Foreign matter, such as dirt and lint from the operators clothing and various sources, can also cause scratches in the work. A wash stand for frequent use by the operator is recommended for all lapping departments.

LAPPING RULES LAPPING RULES A lap should be softer than the part to be

lapped. It is more difficult to lap soft metals than

hard metals. Final finishing should be done only with a

charged lap lubricated with thin oil, naptha, gasoline, spindle, etc.

Final finishes are best obtained with no loose abrasive on the plate. Use the embedded abrasive granules in the surface of the plate and a very thin lubricant.

Tungsten carbide is best lapped with a Diamond compound.

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