Honing is the finishing of internal dimensions of automobile cylinder heads and other components when an excellent and accurate finish is required.

Super finishing is the production of very high finishes, as high as 0.02 um, on the outside diameters of components and inside diameters of bearing rings, bearing races and all other components where friction is to be reduced to the barest minimum.

Honing and Super finishing are generally performed with squire, rectangular or specially shaped sticks or blocks. Honing stones can be used for all forms of honing, vertical, horizantal and flexible or oscillating.

Honing can vary from bore diameters of approximately 25mm to 900mm, on components of up to 9 meters in length. Stock removals can be as high as 21.3 cu.cm. of metal removal per minute while finishes up to 0.05 um are possible with better control.

Ion honing, the abrasive stones are held in the Honing head in sets of 4, 6 or 8 pieces. The Honing Process comprises longitudinal and rotary motions of the honing head to generate a cross hatch pattern.

This pattern is necessary to provide lubrication by retention of cutting fluid. The cutting fluids normally used are straight cutting off, kerosene and mineral seal oil.

Super finishing is generally done in stages of 2, 3 or 4. Roughing is done with White Aluminium Oxide stones of grit sizes 400, 600 and 800. The finishing is done with Silicon Carbide stones of grit sizes 800, 1000 and 1200.

Factors that affect Honing and Super finishing are

• Work piece quality prior to operation

• Machine rigidity and condition

• Machine settings

• Cutting fluid and

• Stone quality.

Certain Honing & Super finishing stones, particularly when used for steel, are treated with sulphur to increase stone life and prevent loading.

Some Useful hints:

1. To avoid glazing, reduce spindle rpm, increase reciprocating speed or use softer grade of stone.

2. To avoid tapered or out-of-form work due to excessive wear on stone, increase spindle rpm, reduce reciprocating speed, reduce pressure or use harder grade stone.

3. For components having a thin wall section and / or comparatively soft stone.

4. To avoid excessive heat generation, use copious flow or coolant, softer grade stone and lower grinding pressures.

5. Hardness of the stone should be decreased as areas of stone in contact with work increases and vice versa.