Grinding and Other Abrasive Processes

the 5 parameters of grinding wheels

1 abrasive material. 2 grain size. 3 bonding material. 4 wheel grade. and 5 wheel structure.

what are the three types of grain actions

1 cutting, where the wheel projects far below the work surface forming chips. 2 plowing, where the wheel projects into the part but deforms instead of removing material.3 rubbing, causing only friction and no penetration

external center less grinding

a grinding wheel spins against a work part. The work part is held in place by a rest blade and moved with a regulating wheel. the regulating wheel is angled to encourage forward movement of the part during its slow rotation.

Truing

a procedure that not only sharpens the wheel, but also restores its cylindrical shape. This is done using a diamond pointed tool which is fed slowly across the wheel as it rotates.

external cylindrical grinding

aka center type grinding. resembles a lathe, except the tool holder is replaced with a powered grinder. generally used for products that are near net size and heat treated such as crank shafts, bearing, and bushings.

center less grinding

an alternative for external and internal cylindrical surfaces. the two types are external and internal center less grinding.

grinding fluids

are similar to those in cutting operations. mixtures of water and oil most used do to its low risk of fire.

reasons for grinding being important to manufacturing

can be used on all types of materials. can be used for extremely fine surface finishes. close tolerances are also possible.

dressing

consists of breaking off the dulled grit and exposing new sharp edges on the wheel, and removing chips clogging the pores . This is done by rotating the wheel against an abrasive stick at high speed.

abrasive material

different material are suited for different materials. the Fri ability refers to the ability of a material to re sharpen itself with a fried surface.

attritious wear

dulling of the individual grains to a round surface. often caused from chemical reactions and high temperatures.

surface grinding

generally used to grind flat surfaces. horizontal spindle most common for this procedure. plunge feeding is when the shape of the wheel shapes the part without moving transversely across the part.

participles of grinder wheel wear

grain fracture. attritious wear. and bond fractures

grinding vs milling

grains in the teeth are smaller and more numerous than the teeth in milling cutters. grinding speeds are higher than milling speeds. grinding wheels have a very high negative angle. grinding wheels are self sharpening.

advantages of creep feed grinding

high material removal rates, improved accuracy for formed surfaces. and reduced temperatures at the work surface.

bonding materials

holds the grains of the cutting wheel together.

Wheel grade

is a measurement of the wheels bonder strength. this has a direct relationship to the amount of bonder present in the wheel. Uses a grading system of soft to hard

Open Vs Dense Wheel Structures

open contains a large ratio of pores to abrasive grains. dense contains large grain to pore ratios. Dense wheels are used for great surface Finnish, while open is great for rough cut due to its chip clearance properties.

Internal cylindrical grinding

similar to a boring operation. work piece is typically held in a chuck and rotated. because the grinding is typically small, and rotates at high speeds. used for bearing races and bushing surfaces.

internal center less grinding

similar to external center less grinding. two support rolls are used instead of the rest blade. This process cannot grind the entire work part resulting in lower production rates than external grinding.

grain size

smaller grains produce a greater surface Finnish, but removes less material. Larger grains properties are visa versa. Harder materials require smaller grains sizes. grit size is measured using a mesh system.

Soft Vs Hard Wheel grades

soft wheels loose their grains quickly, used for low material removal rates and hard materials. Hard wheels retain their abrasive grains, useful for high material removal on softer materials.

general grinding procedures

surface grinding. Cylindrical grinding. center-less grinding. creep feed grinding. and others

infeed

the depth of a cut made by the grinding wheel

crossfeed

the width of the cut made by the grinding wheel

creep feed grinding

used for cuts 1000 to 10000 times greater than conventional grinding. to accomplish this the grinder is fed slowly. can be used for flat and cylindrical objects alike. aka deep grinding in europe

cylindrical grinding

used for rotational parts. Broken up into two main types. External and Internal rotational grinding

wheel structure and grade

wheel structure refers to the relative spacing of the abrasive grains in the wheel. wheel structure measured using a open to dense structures.

Grain Fracture

when a portion of a grain breaks off, the remaining fragments of the grain become the new cutting surface. the tendency for the grain to fracture is called fri-ability.

wheel loading

when chips in the material get caught in the pores of the grinding wheel. Causing grinding efficiency to decrease.

Bond fracture

when the grains are pulled from the bonding material. This is usually the product of attritious wear because sharp edges of the grain tend to not stick.