Abrasive Grit Sequencing and Removal Estimation: Route Design from Coarse Grinding to Final Polishing

The goal of a grinding/polishing route is to obtain a true, deformation-free surface in the shortest time. Two principles govern the design: each step must remove enough material to fully eliminate the scratches and damage layer of the previous step, and the grit-size jump between adjacent steps should not be too large. Poor sequencing markedly lengthens polishing time or leaves deep residual scratches.

Sequencing Principles and Removal Estimation

As a rule of thumb, scratch depth is of the same order as the abrasive grit size or a fraction of it, and the material thickness removed by the following step should be about 3–4 times the previous scratch depth to fully eliminate the prior damage within a reasonable time. An excessive grit jump (for example, from P400 directly to 1 μm polishing) overloads the final step. A common mistake is insufficient grinding time compensated by prolonged polishing, which instead introduces deformed layers and relief.

Typical Grinding/Polishing Routes

For a general steel specimen: grind stepwise with SiC waterproof abrasive paper P180→P320→P600→P1200 (adding P2500 when necessary), replacing the previous scratch pattern at each step and rotating the specimen 90°; then polish stepwise with diamond suspensions of 9 μm→3 μm→1 μm; finish with 0.05 μm alumina or colloidal silica if required. Soft metals (aluminum, copper) can go from P1200 directly to 3 μm diamond; hard materials (ceramics, hardened steels) may add a 6 μm step. When the cutting damage layer is thick, the first grit must be coarse enough to remove the deformed zone quickly.

Time and Process Control

The time at each step is governed by complete renewal of the scratch pattern, which can be spot-checked under a metallurgical microscope. Pressure and speed are adjusted to the material: harder materials tolerate higher pressure and speed, while soft metals need reduced pressure to prevent abrasive embedding. Consumable matching is equally important—the combination of abrasive paper, polishing cloth, and suspension must suit the machine speed and cooling conditions. Automated grinding/polishing equipment ensures consistent pressure, speed, and time, improving reproducibility in batch preparation.

Practical Tips

• Each step removes about 3–4 times the previous scratch depth; avoid large grit jumps.
• Typical route: grind P180→P1200, polish with 9→3→1 μm diamond, finish at 0.05 μm.
• Change steps only after the scratch pattern is fully renewed; never compensate for insufficient grinding by prolonged polishing.
• Adjust the route to material hardness; specimen evaluation and the actual operating procedure shall prevail.