The Tapping Screw is used to "re-true" or re-tap the threads on the bed, just to the right of the needle plate, of your Singer Featherweight 221.
Attachments such as the amoeba-shaped embroidery and darning feed cover plate, buttonholer feed dog coverplate, underbraider, as well as new accessories like our ever-popular Featherweight Accurate Seam Guide are all secured to the bed of the machine via one of these threaded holes.
Be sure to watch the video under the video tab.
*You will notice that your screw has been coated with a corrosion preventative so it will be a tad oily.
*This tutorial is for the Singer Featherweight 221 model in original black, white or tan. It will work for the Featherweight 222 as well, but with the throat plate on a 222 being made of steel (rather than aluminum, like the 221 model), this technique will rarely be necessary.