I've been doing a lot of ruffling lately and wanted to find an easier/quicker way before making this skirt. I had no desire to pull miles of thread for this one.My serger would allow me to gather by changing the tension settings. We did the same with another friends serger. That got me to thinking I might be able to gather by changing tension on my sewing machine. Sure enough it works. Now this type of gathering is not as even and beautiful as if you ran two or three rows of thread and pulled it up yourself. But, honestly, unless you are sewing an heirloom garment that requires intense attention to detail, this will work just fine.
How to gather with this method?
Set your machine to the longest stitch. Move your top tension to a higher number. The higher the number the more gathers you will have. Not gathered enough, raise the tension number. Too many gathers, lower the tension number. Make the adjustments until you get close to the ratio you want.
When you sew your ruffle, leave the beginning and ending threads long so you can adjust your ruffle some when you go to attach it to your garment.
I've used this ruffle method on sheers, t-shirt type knits, and quilter's cotton.
Make sure you reset your machine tension before sewing normally again.
Those of you with newer machines may need to turn off the auto tension in your machine. Check your manual for this feature and how to turn it off. I've checked with all major manufacturers education departments. All of the machines made with a long gathering stitch are able to gather this way. We have come across an older (more than 20 yrs.) Bernina with a shorter (#4 length) stitch length and it did not gather well. I also found someone with a newer Janome who couldn't get her machine to do the gather. She has an auto tension and needed to turn it off in her control panel, per the Janome educator.