Grinding wheel bonds

The bond is one of the main elements of a grinding tool since it holds all the wheel constituents together. After the necessarily very thorough mixing of grains, bond composition and any filler grain used, a "green compact" is pressed in the wheel press. It has no mechanical strength at all as yet and must therefore be handled very carefully. After a short drying phase the "green compact" enters the firing oven, where the bond is sintered and achieves its final strength. The pore-forming agents mixed in for the high porosities burn out without trace during this operation and leave behind the structure of the wheel.

The composition of bonds must be such that they are neither attacked nor dissolved by the coolant emulsions. In addition, the particular bond (type of bond) must be able to survive the contact zone temperatures in the grinding process without damage, i.e. without showing any changes. The bond determines – as has already been referred to under "Hardness" – the static hardness of the grinding wheel.

The following bonds are currently used:

Bonds for CBN and diamond:

• vitrified bond (V)
• resinoid bond (B)
• brittle bronze bond (sintered metal bond)
• electroplated bond

Bonds for corundum and silicon carbide:

• vitrified bond (V)
• resinoid bond (B)
• fibre-reinforced resinoid bond (B)
• rubber bond
• polyurethane bond (P)

*Not every wheel producer uses all types of bonds.

The modern vitrified low-firing bonds occupy an important position. They are produced by synthesis in most cases and already reach their hardness and strength at oven temperatures from about 590ºC to approx. 950ºC. They were specifically developed for diamond, CBN and sintered corundum. At higher firing temperatures these abrasives would be destroyed (oxidised) or – in the case of sintered corundum – fused to lumps which can scarcely chip.

Note: Meister Abrasives AG still produces all bonds in house by controlled mixing of raw materials. A virtually unlimited diversity of combinations is therefore possible.