Flap Wheel Grit for Good Finish?

[SteveHGraham]

I got myself some Walter Enduro-Flex flap wheels in 40 grit, and I used them today to shape some parts I fabricated. They work great. They eat metal in a hurry, and you can trim them for more life.

The finish they leave is a little coarse. I'm thinking of springing for a package of finer wheels. They have 80 and 120. What's the best choice, going up from 40?

They're not cheap, so I see no point in experimenting without seeking advice first.

[carlquib]

I like to go straight to 120 from roughing. With an angle grinder it doesn't take long to clean up the scratches from the course grit. I also make sure the abrasives are tailored to the material. I have separate abrasives for steel, stainless steel, aluminum, etc so I don't cross contaminate but you might not need to do that. I do like to match the abrasive to the material. It is much easier to grind aluminum with an abrasive made for aluminum. If you have to use a wheel that is made for steel to grind aluminum they load up and don't work well. I am a fan of Walter abrasives, especially their slicer wheels, good luck with your project.

My name is Brian and I'm a toolaholic.

[BadDog]

I've got 40, 80, and 120. 40 for moving metal, fit up, beveling for welding, and removing a bead for the cases where I don't want to leave the weld bead in the finished product. And I also will usually jump to 120 before paint. The 80 is mostly for cleaning paint, scale, rust, and lighter dressing work; though I've been known to go straight from cut-down to finish with 80...

[choprboy]

I use them all the time; 36, 60, and 120 grit. Infact, unless I am bulk grinding off large chunks of metal, I use them almost exclusively and find them much easy to control grind depth and finish compared to a hard disc. When brand new they will cut aggressively, but pretty quickly wear off a bit and become more of a sanding action. You can press or change contact angle to get more aggressive cutting. 36 and 60 grit for quick cutting down of weld beads, 120 (or very worn 36/60) for final grinding and blending. I actually clamped my angle grinder with a 120 wheel in the lathe tool post the other day and used it to grind a part face smooth.