Honing is an abrasive machining process that produces a precision surface on a metal work piece by scrubbing an abrasive stone against it along a controlled path. Honing is primarily used to improve the geometric form of a surface, but may also improve the surface texture.


Precision honing produces super finished components to be used in hydraulic applications which require very good form accuracy. The improved shape after honing results in a higher precision component.

Hycom Engineering has KADIA Honing Machine in-house to achieve geometrical accuracies required for hydraulic applications. It also offers subcontract honing facility to other manufacturers of Hydraulic components. While the tolerance on diameter is very close, the geometrical accuracies are equally important.

The spool in valves are designed to slide with least possible clearance. This clearance controls the leakage between the spool and bore in the spool body. The roundness and straightness of the bore beyond certain permissible valve create a camber or banana shape of the bore. The cylindricity error so caused reduces the clearance between the bore and spool and causes stickiness of the spool. To overcome this, the clearance needs to be increased which in turn increases the internal leakage over the spool and load holding ability gets reduced. If there is a taper from one end to other end of spool or bore, it causes an axial thrust on spool and makes the spool movement by hand difficult.

The cylindricity can be due to one of the following.

Barrel shape, taper, straightness error, eccentricity between different bore segments, skewed axis etc. These kind of defects in the valve body bore for spool can be over come by honing the bore using a precision honing machine such as Kadia multi-pass honing machine.

Kadia Honing Machine

Hycom Engineering has KADIA U6 Honing machine. KADIA is the acknowledged expert in this field and is in worldwide demand as innovative problem solver with many years of experience and unique know-how.

KADIA U6 is a Multi Pass Honing machine which ensures each micron is removed by about 5 to 10 passes. Hence, material is gradually removed and there is no burr formation. Additional brushing dislodges even the micro burrs that may be formed. The honed surface with cross hatchpattern provides pockets for oil retention. Honing accuracy depends partly onbore accuracy before honing but correction to camber error and taper is possible.

FFor a typical Spool Bore of 18dia x 125 lengths, the following results can be achieved:
Honing allowance that is normally provided - 30 to 50 microns
Surface finish of the honed surface: better than 0.10 microns Ra.
Cylindricity over the full length: better than 2 microns.
HHoning Bore diameter range: 6 to 32 mm
Honing Length max: up to 280 mm