In addition to the quality of the abrasive grains, the grit size and the concentration of the grains in the abrasive layer, the bond has decisive influence on the grinding performance. All sorts of different grinding tasks can be optimally tackled with various adapted bonds. For this, we have more than 400 self-developed bonds at our disposal.
Klick on the types of bond to know more.
Sintered metal bonds are predominantly bronze alloys and distinguish themselves with their particular high hardness. The abrasive grains are tightly enclosed, which leads to the grinding wheel appearing “blunter”, but also to significantly longer tool life and higher shape retention. In contrast to resin bonds, metal bonds generate more grinding heat and shallower depths of cut have to be used if the protrusion of the abrasive grains from the bond is not maintained (see Haco-Flex). Metal bonds are ideal for profiles, small radiuses starting from 0.02 mm, thin wheel widths and smallest grinding pins starting from ø 0,18 mm as well as when grinding materials subject the bond to high levels of wear. Our metal bonds can be eroded very well and are very wear resistant. We possess a large selection of various metal bonds suited for different applications.
Metal bonds can be used wet (oil, emulsion) or dry. They should be dressed with rotating silicon carbide wheels or by EDM (not with stationary dressing tools or metal bonded dressing wheels). The cutting speed can be between 2 m/s and 30 m/s, while the optimum usually lies between 20 m/s and 25 m/s (guidelines).
Specially for creep feed grinding with high feed rates and deep depths of cut on the newest CNC machines we have developed metal hybrid bonds with a lot of bite (SHARK-LINE). They have a more porous bond structure and thus generate less grinding pressure and in con-sequence less heat. They are designed for grinding with oil. Cutting speed: 14 m/s (guideline).
Resins containing the abrasive grains and fillers are used as the binding agent with which the grinding characteristics of the bond can be selectively steered. Grinding wheels with resin bonds offer rapid and cool grinding, can be used for dry and wet grinding and generate only low grinding forces. Resin bonds can be used for polishing, creep feed grinding with high stock removal rates and anything in between. In short, it is the most universally applicable bond which also happens to be the cheapest. They should be dressed with rotating silicon carbide wheels (not with a stationary dresser or a metal bonded dressing wheel). The cutting speed ranges usually between 15 m/s and 35 m/s, but the optimum lies somewhere between 25 m/s and 28 m/s (guidelines).
Resin ceramic bonds work with the smallest grinding pressures, can be used in wet or dry grinding and with the finest as well as the most coarse grit sizes. Our resin ceramic bonds have a broad range of application. Nevertheless, we have a large number of application-specific resin ceramic bonds.
For deep grinding, particularly for tool grinding with high stock removal rates, we have developed resin hybrid bonds that distinguish themselves with their long tool life and high profile retention. Thanks to their excellent ability to divert heat away, high stock removal can be achieved. Grinding wheels with resin hybrid bonds are only used wet (oil) and on CNC machines. Materials to be machined are mainly carbide and cermet. These bonds can be spark eroded (EDM) with the right body.
Bakelite (thermosetting plastic), to which fillers have been added along with abrasive grains, is used as the binding agent. This type of bond exerts more pressure and can be used with fine abrasive grains due to the polishing effect associated with the pressure. Grinding wheels with bakelite bonds are nowadays only used for polishing.
A mixture of meltable glass powder, filler and abrasive grains constitutes the vitrified bond. In contrast to the metal and resin bonds, the vitrified bond offers amongst others the advantage that a certain pore volume can be produced. Due to its porosity, the bond is suitable for materials producing long chips (steel). Vitrified bonds are mainly used in conjunction with CBN. As the bond is made from glass, the grinding wheels cannot withstand major impacts or temperature shocks. Uninterrupted cooling is therefore always required. The vitrified bond provides cool grinding with low grinding forces and can be easily dressed on the machine with rotating dressers. Hence, it is particularly suited for the produc-tion on a large scale and the production of thin workpieces. The cutting speed ranges usually from 20 m/s to 45 m/s, while the optimum is around 30 m/s to 35 m/s (guidelines). We manufacture grinding tools with vitrified bonds up to a diameter of ø75 mm.
Ceramic bonds are used in conventional grinding wheels that contain neither diamond or CBN but silicon carbide or corundum. We do not offer such wheels except as dressing wheels for dressing our diamond and CBN grinding wheels. The ceramic bond consists of meltable glass powder, filler and abrasive grains. It can be used to grind “soft” (<50 HRC) workpieces. As the bond uses higher grinding forces and is subject to higher wear such wheels are not recommended for harder materials.
This bond is electroplated onto a base body made from steel or carbide. As a result of this coating process, the bond has large chip spaces. The galvanic bond is particularly suited for coating profiled base bodies. Profile accuracy does depend on the grain size though. Due to the large grain protrusion, the electroplated wheel has good grip and leaves the workpiece with a very rough surface. With increased use, the grip is reduced as the abrasive cutting edges are worn away. Depending on the size of the base body, it can be worth it to recoat the body when the thin abrasive layer has been used up. It can be used in wet or dry grinding. The grinding speed when grinding without coolant lies between 8 - 18 m/s (diamond) and 15 - 25 m/s (CBN), when grinding with coolant between 15 - 25 m/s (diamond) and 25 - 40 m/s (CBN).
Advantages of sintered bonds
While the abrasive layer is massive in sintered bonds, it consists only of a thin layer in electroplated bonds. When the abrasive grains that were electroplated are blunting or breaking out, grinding is no longer possible. Not with sintered bonds where the whole thick abrasive layer is permeated with abrasive grains and where grinding is possible until the very last grain. Hence, sintered bonds have massively higher durability and are therefore very economical. In addition, sintered bonds have better edge retention than electroplated bonds and result in finer surfaces when using the same grit size. Furthermore, electroplated bonds are not suitable for small grit sizes.
You can find the above mentioned information on a few pages in chaptre 1 (general information) of our catalogue.
Haefeli Diamantwerkzeugfabrik AG
Tel: +41 (0)44 377 80 50
Fax: +41 (0)44 377 80 60