Хонинговальные головки

3.3.1 Importance of Crystal Size A limitation of the electrofusion route is that the resulting abrasive crystal structure is very large; an abrasive grain may consist of only one to three crystals. Consequently, when grain fracture occurs, the resulting particle loss may be a large proportion of the whole grain. This results in inefficient grit […]

As with diamond, CBN grain grades are most commonly characterized by toughness and by shape. Toughness is measured both at room temperatures and at temperatures up to >1,000°C comparable to those used in wheel manufacture, the values being expressed in terms of a toughness index (TI) and thermal toughness index (TTI). The details of the […]

6.6.1 Introduction A number of considerations must be taken into account when selecting vitrified bond for diamond that places different demands relative to conventional wheels. These are primarily the effects of: Hard work materials Low chemical bonding High grinding forces Reactivity with air at high temperatures These considerations are discussed as follows. 6.6.2 Hard Work […]

In addition to the stationary tools for traverse dressing, full forms can be dressed simultaneously using form blocks. These are blocks that have a layer of diamond either sintered or directly plated and molded to the form required in the wheel. They are used especially in surface grinding where the block is set on the […]

Nonporous superabrasive cannot, in general, be dressed with diamond tooling. Truing can be performed for some softer CBN bonds, such as resin, using diamond nibs or rotary diamond traversing discs, but, in general, most wheels are trued and conditioned using conventional abrasive blocks or wheels. In the case of diamond, this can sometimes be completed […]

Common roughness specifications (marks) on part drawings are shown in Figure 2.7. This gives both the current standard practice, especially in Europe, and the older machining marks still seen Cross-hatch grind pattern from a Concentric rings grind pattern from a face grind operation, e. g., shoulder plunge or angle approach shoulder kiss or double disc […]

3.7.1 Indentation Tests Fundamental mechanisms of crack formation and spreading in the case of brittle-hard materials were carried out by Lawn and Wilshaw [1975]. The stressing of a ceramic surface with a cutting edge causes hydrostatic compression stress around a core area in the subsurface of the workpiece. This leads to a plastic deformation of […]

Holding the abrasive section together on the wheel body has already been discussed. A second problem is how to hold the wheel body on the machine spindle. Centrifugal forces cause the wheel to expand radially both on the outer diameter and the bore. It, therefore, must also contract axially. The problem is, therefore, to prevent […]

As with all new technologies, it took significant time and application knowledge to understand how to apply SG. The abrasive was so tough that it had to be blended with regular fused abrasive at levels as low as 5% to avoid excessive grinding forces. Typical blends are now • 5SG (50%) • 3SG (30%) • […]

Interestingly, GE also developed a grit-type GE 550 that is a microcrystalline product; this could be considered the “SG” of CBN grains. It is extremely tough and blocky and wears by microfrac­turing. However, just like SG grains, it also generates high grinding forces and is, therefore, limited to use in the strongest bonds, such as […]