After a while we collect remnants of batting from all our quilts. I join larger pieces together and use them in other quilts. But what about the smaller pieces? For years I joined pieces of batting using herringbone stitch by hand which is slow and tedious. If I tried using my zigzag stitch on my machine I would often create waves from stretching the batting. Recently I purchased a quilters ditch foot for my Janome (S foot). This foot has a center guide where you can butt both pieces of fabric against it thus making this task very simple with the result of a flat join. RULE - make sure your edges of each piece of batting you are stitching together are cut straight.
I increase my zigzag width to 6.5mm and stitch length to 2. Do a test piece to make sure your stitches are not to far apart (causing batting to stretch) or to close (causing batting to pucker).
I don't recommend using lots of little pieces of batting for large bed quilts - however great for those smaller projects (i.e. wall hangings).
Batting butted each side of the foot guide.
Small pieces of batting zigzagged together using the ditch foot. There is no loft in the joins - they lay flat.
Notice the right side of this piece of joined batting. It wavers as it was not cut straight before the join. It wont lay flat and may cause issues when you commence quilting.
Do make sure you are joining similar weight and loft pieces of batting .
happy quilting