Use this attachment to create a 1/8th-inch flat-felled seam because it folds, presses, and stitches the first row of stitches all in one pass.
This seam finish not only prevents unraveling or fraying, but makes the seam very strong. It also gives the finished garment a clean finish on the inside. A flat-felled seam is commonly found on denim jeans and men's dress shirts as well as on reversible garments. I've even seen this feature instructed in vintage patterns for boy's and men's pajamas. It adds one more touch of professionalism to a hand-made garment.
*Using this attachment, while still accommodating a 1/2-inch seam allowance (e.g. Oliver + S patterns), I trimmed 1/8 inch from each of the seam allowances prior to stitching so that the finished seam would finish with the correct seam allowance according to the pattern.
Referring to the photographs above you will begin by spacing the top seam allowance 1/8 inch to the left of the bottom seam allowance as shown in the photo above. Finger press and fold the start of the seam so that you can stitch 2-3 stitches to secure the folds in place. With the needle still in position, maneuver the bottom seam allowance into the Felling foot so that it curves up and around - sewing slowly, carefully begin stitching to allow the bottom seam allowance to fold over the top seam allowance so that the folds can be stitched in place for the first stitching line.
Simultaneously, the attachment is folding, pressing and allowing the needle to stitch the initial seam enclosed. Press the enclosed seam so that you can make the final pass with the attachment.
Using the Feller attachment for the second pass, slip the stitched fold up into the attachment with the right toe set up against the outside of the first row of stitches. Allow the fold to carefully pass under the foot while stitching it in place for the finished Flat-Felled Seam. The 4mm Feller Attachment makes a dainty, 1/8" narrow flat-felled seam.
LOW SHANK: fits the Singer Featherweight 221, 222K and all low, vertical shank Sewing Machines (i.e. 15, 27, 28, 66, 99, 185, 127, 128, 192, 201, 206, 237, 306, 319, 320, 328, as well as many other brands besides Singer)