Removing Grinding Scratches from Steel Surfaces
Grinding wheels cut steel quickly but tend to leave visible scratches behind. Getting rid of those scratches involves working through a series of increasingly fine abrasives, and with the right technique and materials, a smooth finish can be achieved.
By Alex Foster3 steps
Using sandpaper is one of the cheapest and easiest ways to polish metal.
The grinding wheel ranks among the most effective tools for shaping and cleaning steel. Because these high-speed tools remove material rapidly in large amounts, they frequently leave marks on the finished part. Deep gouges produced by a very coarse grinding wheel are typically best addressed using progressively finer grained stones. Even so, the finest stones can still leave marks behind, and properly eliminating those marks requires polishing.
Step 1
Set the steel part that will be polished into the vise so that it sits parallel to the vise or the ground. Keeping the sanding block flat against the part becomes easier this way. Removing grinding marks means taking down the material at the high points of those marks until they match the low spots, while avoiding making the low spots any deeper.
Step 2
Wrap 40-grit sandpaper around the sanding block, keeping the paper taut and flat. Remove steel using long strokes with slow, steady pressure. Keep the block square and flat against the steel so that the whole surface of the sandpaper makes contact with the part. Keep sanding until the surface looks uniform. When finished, it should have a dull luster.
Step 3
Work through progressively finer sandpaper on the part, moving from 40-grit down to 320-grit. After the 320-grit sandpaper is done, the grind marks should be gone completely. For a polished surface, switch to 600-grit sandpaper with water to take out the very fine scratches that the 320-grit left behind.
