I don't know if I mentioned this before, if I didn't, I wished I had. But they make "flap wheel" grinding discs. Instead of a hard surface grinding stone, these flap wheel discs have multiple layers of zirconium impregnated flaps, or sand paper if you will. The are heavy and last a long time considering the material you are removing. When I make anchors, I sand and polish the work smooth and to a shine with these. You can't imagine the finish they result in vs grinding multiple stages of grit and then having to polish. These do it in one step. I have used various grits and find that the 80 grit makes just as clean a polish on carbon steel as 120 grit does, but 80 grit discs last longer. I also find that the quality of the discs at Home Depot or Lowes is not good, they have fewer flaps per disc, and they run smooth faster. I find my discs at either a welding supply or even my nut and bolt supplier has them. They look like this.
But after 40 anchors, I find out now that ceramic coated flap wheel discs is better for use on alloys such as stainless steel, as it is reported to bring it to a better polished finish. I don't find these at my welding supply, you may have to order these discs if you were going to use them. They have a red color to them.
But the zirconium discs work fine on stainless, they just don't last as long. But you could do 30 scuppers on on disc, so no worries on that. Generally, these discs run me around $8.50 each and you have a choice of 40, 60, 80, and 120 grit. I have stepped my work from 40 to 120 and not found that really beneficial. Working with steel, especially stainless, is not like wood. The surface your after in a polished finish comes from the high speed surfacing, not from the grit in normal steel, but stepping the grit on stainless will result in a more polished surface. Since the scupper comes polished, a couple of discs, such as 80 and 120 may result in a matching polished finish.
And as
@Gym says, wear non flammable material and gloves...if you were doing this at dusk, you would see the steel glowing cherry red! I have had a third degree burn from this, so do be careful. If your removing metal, it is getting towards the melting point! Be sure you know the size of your angle grinder, the discs come in different arbor hole sizes, a 5/8" arbor is common on a home owner size grinder. Most grinders however are 7/8" arbor. So most discs sold are 7/8" size. But the home centers carry plenty of 5/8'" discs, that are cheap and won't cut as well or last as long. How long they last isn't as important for this project, because it will make it through the project just fine. But they don't cut and well, the bounce more, and they don't polish as well. So if you can avoid that it is better. You may use your grinder more often for other projects if you knew you could get these abrasives, that make your life MUCH easier than a solid stone type wheel or flat surfaced abrasive. Also be aware some of these discs come threaded, and others don't. Know what you have and what you need. Hope this helps!
