This excellent Wera screwdriver has a non-slip tip that fits the larger screws on most vintage sewing machines. It is a perfect fit for the motor mounting screw on a Featherweight, where the safety plastic coating on the shank prevents damage to the paint on the arm of your machine.
221/222 bobbin winder arm
221/222 electrical connection attachment screw
221/222 stitch length lever tension scfrew
Singer 301 motor retaining screw
And many other Singer screws