Technical flap disk recommendations please

Ebay, cheap and buy in bulk.

I give about a buck each vs. Almost 4 bucks each around here. And 4 of my cheap ones last about twice as long as welding shops around here so its about 1/2 price when it comes to use...

 

It must have been long ago
https://www.jalopyjournal.com/forum/threads/tech-man-i-mean-tman-post-the-flapper-tech-piece.1551/

 

Klingspor makes pretty good abrasives of all types.
https://klingspor.com/

 

Don't use flap disks on sheet metal. Way too aggressive and grind away too much of the surrounding metal.