Grinding wheels promise longer life

Sintered aluminium oxide grains in a vitrified-bond grinding wheel offer significant performance benefits over fused grains.

Sintered aluminium oxide grains in a vitrified-bond grinding wheel offer significant performance benefits over fused grains, rivalling the performance of superabrasives like cubic boron nitride (CBN).

However, to maintain their sharpness and strength, sintered grains need a low-temperature bond, which is weaker and does not hold profile form as well as high-temperature bonds.

The new range of Tyrolit CSS-Ultra vitrified grinding wheels for OD (outside diameter) grinding solves this dilemma, for the first time offering users real choices.

The new bond has extreme form-holding characteristics, requiring minimal dressing, leading to long wheel life.

At the same time, it allows the creation of highly porous, free-cutting wheels, avoiding burn and chatter marks on the component.

Notably, the bond system can be used with all abrasive grains, either expensive sintered varieties or conventional fused grains, or a mixture of the two types in any proportion.

In other words, users can now specify their own bespoke grinding wheel by optimising the cost and performance characteristics so that they last longer, or cut faster (up to 125m/s) or with lower forces for producing delicate, difficult-to-machine parts in exotic materials.

To assist the correct choice of wheel for different applications, CSS-Ultra products are manufactured in four colour-coded ranges, including orange for grinding crankshaft main and pin bearings, and blue for face and journal grinding.

In addition, a range of highly porous wheels using the same bond will be launched shortly which can be used for creep feed grinding of turbine industry components.

Compared with using aluminium oxide grinding wheels with fused abrasive grains, price-performance ratios can be increased by as much as 50% using CSS-Ultra, claims Tyrolit.

Application examples include grinding a C38MOD crankshaft of Rockwell hardness 58 to 62 HRC on a Naxos machine at 50m/s.

A 30% increase in infeed rate was achieved when grinding the shoulders.

Two hubs were machined per 0.04mm dressing.

A 30% reduction in dressing amount to 0.005mm as well as a smaller variation in surface finish and 10% lower part temperature resulted when using a CSS-Ultra wheel to machine 100CR6 spherical rollers on an FAG grinder at 80m/s cutting speed.

Fifteen rollers were produced per dressing.

When grinding a turbocharger rotor on a Schaudt ZX11 at 50m/s, wheel life was extended by 50%.

Taps were also produced efficiently without burning, even those with narrow thread angles, as evidenced by grinding of M5 to M8 high speed steel taps, hardened to 64 to 66 HRC, on a Reishauer GBA at 80m/s.

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