This is a tutorial comes from I Heart Jenny's Art for how to make a hat with a bill from an old sweater. It's actually part 3 of a three part series (Part 1: Elbow Patches, Part 2: Leg Warmers). So all you need for this project is the body of the sweater and a piece of transparency paper (you can find this at Staples).
Step 1: Preparing the Bill
Take a ball cap and trace the bill. This is your insert pattern. Now add 0.5" all the way around your insert pattern. You've now made yourself a bill pattern.
Here's my big secret. Transparency paper. You know, like you used in school for the over head projector? It makes a great bil insert. I don't like using cardboard like some people do because it gets gross when wet. This stuff is fine. I haven't tried to wash/dry it. But otherwise it works great. So take a sheet of transparency paper and cut a bill insert out
Using your bill pattern, cut 2 out of your sweater
Sew bill pieces together with 0.5" seam. Snip around the edges
Insert the bill insert. pin. Top stitch 3 lines equal distance apart. I used 1/2 a presser foot width as my measurement
Step 5: Making the Band
Measure around your head. This is your headband length. For the headband portion cut 2" strips out of the sweater down the side, then cut to the length just measured. Cut an equal length strip for the inside. If you do not have enough sweater left, use some scrap jersey.
Sew your headband strips, both inside and out, together to make 2 loops.
Step 6: Attaching Bill and Band
Find the center of your outer headband. Pin to the center of you bill. Working out from this point, pin your bill to the outer headband. Repeat with inner.
Now sew together inner and outer headband all the way around, including bill section.
Step 7: Adding the Cap
Cut out circle from back side of sweater with a radius of 8.5" to get a good amount of fullness (based on an average 22" headband size).
Pin edge of circle to raw edge of outer headband, pleating as you go. Sew
Step 8: Finishing Touches
Finish raw edge of inner headband as you like, I surged it.
Turn inner headband up so it covers seam from step 7.
On outside of hat, on the upper hat portion, stitch as close to the seam from step 15 as you can. This will hid all the unfinished edges on the inside of your hat.
Check out more tutorials here: http://iheartjennysart.com/category/tutorials/