Step 2 - Now that you have a full sleeve pattern, draw a line vertically from the top center point to the bottom center point. If you didn't overlap your papers at all, this will be the line where both halves meet. Now draw a horizontal line from about 1/2 inch below the arm pit point around to the opposite side at the same point. Your lines should make a large cross shape on the pattern. I like to use a rotary cutter and a long quilting rule to slice on these lines. Keep in mind, you need to stop about 1/8 inch from the edge in order to make a hinge. If you accidentally cut all the wear through just put a tiny piece of tape there to hold it in place.
Step 3 - Spread the pattern open the distance you need to add. You should measure along the same horizontal line you cut earlier. You will notice the hinges are working to hold everything in place as you spread it. I like to use a small piece of tape and stick it to my cutting mat. Once you have added the needed width, you will insert scrap paper behind your pattern and on top of your cutting mat. These pieces of paper fill in the opening and once taped down, will stabilize the pattern.
Step 4 - Now you will use scrap paper to add across the bottom to straighten it out. At the hinge, you will see it has created a point. Use your straight edge ruler to redraw a straight line from the right side to the left size and recut the line.
Step 5 - If adjusting your pattern created a small dip at the center of the shoulder cap, use the same technique as Step 4 to even it out. At no point during this process should the length of the shoulder cap curve have changed. This ensures it will fit into your shirt according to the pattern. TA- DA You did it!!! You added width to your bicep area! No More Incredible Hulk Arms!!
For this lesson, I used the slim fit sleeve pattern from Sitting Pretty. It is the pink shirt in the intro photo as well as the closing picture. I am also wearing the Wrap Shirt by EAM.