Mini Tutorial: Mitering Fabric Corner Seam Allowance
The most conventional way to miter fabric corners is by using the corners vertical and horizontal seam allowance edges. Here’s a simple way to miter a fabric corner:
1. In this case, the seam allowance is 1” along all edges. Start by folding and ironing each edge teh worng side of the fabric at teh deisgnated seam allowance (1" here). Repeat on both horizontal and vertical edges inetrescting teh corner.
Once folded and creased, the fabric corner should have two intersecting fold lines which conveniently also depict the corner's seamlines.
2. Fold the fabric corner diagonally toward the wrong side of the fabric such that the crease line intersection point (shown above) falls directly on this diagonal fold. Again, iron as you fold to crease.
As a result, you should have 3 crease lines that intersect at a single point which also depicts the finished corner point. The diagonal crease line will provide a stitching guide for completing the mitering's diagonal seam.
3. Fold the corner such that the vertical edge aligns with the horizontal edge and the diagonal crease line is folded onto itself with lines overlapping as shown. Insert a few pins perpendicular to this diagonal fold to secure this alignment. The corner point should fall directly on the folded edge.
4. Starting at the fabric raw edges, stitch diagonally following the diagonal crease line until you arrive at the corner point. You can backstitch at the corner if your fabric is more structured (medium to heavyweight). If working with flimsy fabrics, its safer to tie the loose threads together instead as backstitch may cause some crinkling and tension in the finished corner.
5. Once stitched, trim the excess fabric at about 1/4" from the stitch line.
5. Slash the corner seam allowance diagonally (as shown above) to allow more flexibility in the finished application.
6. Open the seam allowance edges and direct the seam diagonally in relation to the corner. Iron the open seam allowance flat.
7. Turn the mitered corner application on its right side and align the seam diagonally such that the finished vertical and horizontal edges fall directly on the crease lines applied in Step 1 above. Iron the finished corner and corresponding edges to complete the application.
The finished mitered application should lay flat with a well-defined corner and evenly folded edges. If you fold and iron the crease lines accurately in the initial process and follow them accurately in the stitching process, you should achieve a perfect mitered corner every time.