Basic principles of honing
Definitions according to VDI 3220
Honing is a cutting process where multi-edge tools coated with particles with continuous surface contact between the tool and workpiece are used to optimise the dimension, form and surface of pre-machined workpieces. Between tool and workpiece a change in direction of the longitudinal movement takes place. The finished surfaces are characterised by a cross-hatch pattern on the surface.
Process kinematics today
The work process with honing is a combination of stroke and rotation movement of an expandable honing tool with inserted honing stones or diamond sticks. The result is the surface structure with cross-hatch pattern generated by the honing process. The timing of the honing is defined by quick cutting of the peaks of the pre-machined bore surface. This rapidly achieves a smoothing of the surface.
The cutting speed of the honing is the result of two components:
- the axial speed Va = 12 to 25 m/min and
- the circumferential speed Vu = 20 to 50 m/min.
- The over-cutting angle ∂ of the machining traces should range from 60° to 90°.
Stroke length and position
In order to realise the bore cylindricity, the stroke length and position of the honing tools must be adjusted such that with a standard work stroke approximately a third of the honing stone protrudes at the upper and lower ends of the bore (stroke length = bore length – 1/3 honing stone length). Honing is also possible with blind holes. In this case secondary honing or a stroke delay at the bore end with specially formed blind hole honing tools are particularly important.
The results of the honing process are:
- quick material removal with adherence to tight dimensional tolerances
- high geometrical accuracy also with difficult workpieces
- selectively realisable surface finish with high contact area
In addition to simple through bores, special tools can be used to machine blind holes. Large surface tools can be used to hone without a high cost bores with openings, grooves and wedge profiles.
It is possible to correct the following bore errors
|curvature||conicity||barrel form||lack of roundness||undersize||taper||waviness|