Sheet Metal Trade and SMWIA 2nd Year Practice Test

A flapper wheel is used to blend and finish a surface after grinding. It’s made of many flexible abrasive flaps that conform to the contours of the workpiece. As you grind, the ridges and wheel marks are left behind; the flapper wheel’s flexible flaps wear in and continuously expose fresh abrasive, gently removing those marks without digging into the metal. That smooths and smooths the transition between surfaces, which is exactly what you want after grinding.

Sanding discs can remove some surface marks but aren’t as good at shaping and blending curved areas. A grinding wheel is meant for heavy material removal and tends to leave deeper wheel marks. A wire brush cleans and deburrs but can scratch and gouge, not provide a controlled, uniform finish.