Multilayer grindstone for gear grinding

A multilayer grindstone for gear grinding, the multilayer grindstone comprising:

• a first thread-shaped grindstone and a second thread-shaped grindstone that are fixed to each other, such that the first and second thread-shaped grindstones have a rotational axis that is common to the first and second thread-shaped grindstones;
• and
• a thread-shaped groove that is provided in a first outer circumferential surface of the first thread-shaped grindstone and a second outer circumferential surface of the second thread-shaped grindstone, such that the thread-shaped groove extends continuously over the first outer circumferential surface and the second outer circumferential surface,
• wherein the second thread-shaped grindstone is constituted by abrasive cloths that are laminated on each other, and has a higher elasticity than the first thread-shaped grindstone,
• abrasive grains of the second thread-shaped grindstone have a grain size of F220 to F2000, and are finer than abrasive grains of the first thread-shaped grindstone,
• the second thread-shaped grindstone has a bending elastic modulus of 0.05 to 1.0 Gpa, and
• a ratio of content of abrasive grains in the second thread-shaped grindstone is 1.0 to 20 vol %.