Cutting Edge Density

Cutting edge density is important to understand tool performance during the grinding process. Many researchers analyzed the statistical nature of the cutting edges [KASS69, BUTT68, SALJ88, HOU03, LORT75, etc.].

6.2.1 Definitions Static Cutting Edge Density

Researchers differentiate between grit number and cutting edge number because each grit can have several cutting edges. However, both values are often denoted with the same letter, N. Grit or cutting edge distances are nominated with L and are approximately inversely proportional to the grit or cutting edge number, N (Eq. 6.4, Fig. 6.5) [SALJ88]. Important metrics are also the number of grits or cutting edges per area or per volume, often denoted with the letter C.

N grit/cutting edge density in [1/mm2] L grit/cutting edge distance in [mm]

Shaw estimated the number of active grits per unit area, or so-called approximate grain spacing, from the grit size (Eq. 6.5) [SHAW96, ROWE09]. However, Rowe stressed that wheel structure, depth of cut, and wheel deflection affect the number of active grits [ROWE09, p. 81].

N grit density dg mean grit diameter

ISO 3002-5:1989 defines the static grit number at a certain depth, Nst, as the counted grit number at a certain band depth measured by a quasistationary method such as stylus, thermocouple, or microscope [ISO89]. Figure 6.4 visualizes the cutting edges emanating from the cutting area. The cutting area depth extends in normal direction to the outer tool envelope [SALJ88]. The measurement directions can be in the feed direction or perpendicular for circumferential grinding wheels and honing stones and towards the wheel center or in circumferential direction for face grinding operations [SALJ88].

The apparent contact area is the area between wheel and workpiece after Eq. 6.6 [ROWE09, p. 315]. The real contact area, however, is the sum of all contact areas on the grit tips in the respective depth of cut and much smaller that the apparent contact area (see Fig. 6.4).

Apparent contact area Ac = bseff • lg (6.6)

bs eff effective grinding wheel width lg geometric contact length (Eq. 6.7)

lg contact length

ae depth of cut

deq equivalent grinding wheel diameter (Eqs. 6.15, 6.16 and 6.17)

Linke calculates the grit distance, Kab, for CBN grits under the assumption of spheric grits and face centered cubic model [LINE92, p. 51 f.]. The face centered cubic model has the highest packing density of a cubic structure (74 %) [LINE92, p. 52].

dg grit size

Vcbn volumetric grit concentration in [%]

Updated: 24.03.2016 — 11:54