The broad range of application technology
The broad range of grinding application technology - starting from the rough grinding up to the finishing - requires abrasive bodies that optimally adapt to the requirements of surface quality and tool life. Apart from knowing about the application conditions, selecting raw materials and their combination in correct specification are crucial to the abrasive body’s quality.
A big advantage for our Customers is that there is no minimum order. Customers may order abrasive bodies as single items of any measurement. We would be glad to deliver grinding wheels so that they can be tested and paid for after approval.
From the following descriptions may be gathered an overview of the composition of our abrasive bodies. The material for the abrasive bodies (composition) is defined by the abrasive itself, its grain size, the binder, degree of hardness, and its structure.
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|NK||Normal corundum||Tough grain for alloyed and unalloyed steels|
|EKW||Precious corundum white||Hard and rough grain for alloyed and hardened and tempered steel|
|EKR||Precious corundum pink||High grain toughness compared with precious corundum which for alloyed and hardened and tempered steel|
|EKD||Precious corundum dark red||For alloyed and hardened and tempered steel|
|HEK||Semi-friable alumina||Mixture of normal corundum and precious corundum|
|EKK||Single crystal corundum||High microhardness. Most suitable for high-performance abrasion for alloyed and thermally sensitive tool steels up to 65 HRC|
|SCG||Silicon carbide||Very hard and rough grain for hard metal, glass, cast iron, ceramics|
|KUK||Spherical corundum||Bubble alumina, especially for grinding of rubber and foamed material|
|SGK||Special corundum||Micro-crystalline sintering corundum; as regards hardness and cutting capabilities its values are clearly above those ones of conventional grains. Especially for high-alloyed tool steels up to 65 HRC.|
The binder is for holding the individual grains as long as they have become blunt. Kind and quantity of the binder used influence the degree of hardness and grinding characteristics of the abrasives.
Binding of abrasive bodies
|Designation||Kind of binding||Binder||Characteristics||Fields of application|
|V||Ceramic binding||Feldspar, earthenware, quartz sand||porous, rough, thermally insensitive, water, oil: easily shapeable||Rough grinding and finishing of steels with corundum and silicon carbide|
|B, BF||Synthetic resin binder, fibre-reinforced||Phenolic resin with cooling and stabilizing fillings||dense or porous, tough, elastic, oil resistant, high circumferential speed, cool grinding||Rough grinding and abrasive cutting, high-pressure grinding with zirkonium corundum, profile grinding with diamond or boron nitride|
|M||Metal binding||Sintering metals: bronze, hard metal, wolfram||dense or porous, tough, thermal and pressure resistant, heat, strong holding force||Profile and tool grinding with diamond or boron nitride (wet grinding)|
|G||Galvanic binding||galvanic metal deposition||high grip due to protruding grains||Internal grinding of hard metal, manual grinding|
|R, RF||Rubber binding, fibre-reinforced||Rubber (natural resin)||elastic, cool grinding, oil and water sensitive||Abrasive cutting, control disks|
Degree of hardness
The static hardness (nominal hardness) describes the resistance of the grain against the breaking off from the grain compound. Thus, the degree of hardness does not describe the hardness of the abrasive body, but the holding capability.
When grinding hard, rough material the abrasive bodies soon get blunt due to the high friction wear. Only a soft wheel can guarantee the “self-sharpening-effect” with the grain being subject to relatively low use. However, soft wheels have to be avoided because of the excessive wear.
Friction wear is lower, but grain load is higher when processing soft and tough materials. The grain tends towards splitting and breaking-off. In order to keep within limits the wheel’s wear, this materials needs to be processed by harder wheels having tougher grain. But, the holding period of a wheel that is too hard is too long, so that is starts “lubricating” and shines. At the same time, there is an increase of grinding pressure and temperature in the contact zone.
For hard materials select soft and for soft materials select hard wheels. The smaller grain size and feed speed are and the longer the contact period is, the softer needs to be the grinding wheel.
Grain size along with FEPA
|Coarse||6, 8, 10, 12, 14, 16, 20, 24|
|Medium||30, 36, 46, 54, 60|
|Fine||70, 80, 90, 100, 120, 150, 180|
|Very fine||220, 240, 280, 320, 400, 500, 600, 800, 1000|
Hardness of abrasive bodies
|Designation||Degree of hardness||Fields of application|
|extremely soft||A, B, C, D||Creep-feed grinding and side grinding|
|very soft||E, F, G||Creep-feed grinding and side grinding of hard materials|
|soft||H, I, J, K||traditional metal grinding|
|medium||L, M, N, O||traditional metal grinding|
|hard||P, Q, R, S||External circular grinding of soft material|
|very hard||T, U, V, W||External circular grinding of soft material|
|extremely hard||X, Y, Z||External circular grinding of soft material|
The structure of the abrasive bodies results from the portions of the abrasive grains, binders and enclosed pores. The chip space (pore) needs to be at least big enough that it is capable of receiving the chip amount that is abraded by the abrasive grains in the contact zone. If pores are too small, chips are pressed into the pore and cannot be ejected by centrifugal power and cooling lubricant, which results in high grinding pressure, strong heating, going out of shape, burn marks, and, probably, grinding cracks.
The structure needs to be the opener, the bigger cutting depth and feed speed are.
The structure is referred to by designation numbers 0 to 18. The larger the number, the opener is the structure, which means the more porous is the abrasive.
In accordance with DSA (German grinding wheel committee), abrasive bodies for increased circumferential speed need to be designated by diagonal stripes in one of the listed colours.