I have previously blogged about my hemstitcher and how tempermental it can be. I would blame most of its stitching problems on its "personality" and just try to deal with it. The primary problem I have experienced is skipped stitches. Skipped stitches are very bad because that extra thread can get caught around or under the piercers where they are cut. Usually, I would experience skipped stitchers with either the left needle or the right needle, and occassionally both.
In the past, I would work through the most "obvious" and possible solutions to prevent skipped stitches. Most how-to guides suggest rotating the needles out ever so slightly. I would thoroughly clean, oil, and lube. I would check the threading. I would replace and reset the needles. Often, I could solve the problem enough that I would experience little thread breakage. That was until I worked on a blanket order that consisted of flannel fabric that came from H - E - double hockey-sticks L. If you heard a scream, followed by head banging 2 weeks ago, it might have been me.
The picture on the left shows the stitching along the long grain (the grain parallel to the selvedge edge, also called the warp). You can see the frequent skipped stitches. In fact it skipped so often that I was experiencing thread breaking and thread fraying every 2 inches of stitching. The picture on the right shows the stitching along the cross grain or weft. The stitching would be absolutely perfect - no skips or thread breakage.
My initial thought was there was something wrong with the fabric. It either was a blend or had too much sizing. My hemstitcher will not stitch reliably on polyester fabric blends, but a burn test confirmed it was cotton. I couldn't wash the blanket to rid it of the sizing. Some flannels do not look the greatest after washing, and usually the sizing does help with the stitching. Too much sizing is an indication that the fabric is of lesser quality, although not always. This order was a 45" x 45" blanket consisting of a panel print on the front and a coordinating print on the back. I had very little scrap left over to do any testing to see if it was indeed the fabric. Stitching on other softer flannels was easier, although I was still getting thread breakage.
It took me a while to finally figure out what the problem was. One significant clue is the stitching difference between the long and cross grains. There are distinct properties to these two grains that affect how fabric behaves and also how it behaves as it is stitched. The long grain (warp) consists of yarn that is pulled taut. The cross grain (weft) consists of yarn that interlaces with the long grain. It goes over and under the long grain yarns. If you fray out fabric, you will notice that the cross grain yarn has a wave and the long grain is straight. You can pull the cross grain yarn like a spring, but the long grain will snap. Because of this, the cross grain of a plain weave fabric has a natural, built in stretch.
While stitching, a hemstitcher inserts two needles into a pierced hole. As the needles come up, they swing out pulling the yarns of the fabric apart. The next stitch will hold the hole open. Each hole requires three stitches. The machine has to work harder along the long grain of the fabric because of the inherent nature of that grain. The machine works less hard on the cross grain because of the natural stretch built in.
Ok. So now I knew the problem, but I didn't know how to solve the problem. I have to stitch around all four sides of my blankets, so there had to be a way to adjust the machine so I could stitch and not get anymore skipped stitches. I pulled out my usual help guide in diagnosing stitching problems. The Coats & Clark pamphlet titled The Basics of Hand & Machine Sewing, published in 1995. This is a fantastic pamphlet that covers many aspects of needles, thread, proper tension, etc. I don't know if this is available anymore, as I acquired the full set of Coat & Clark pamphlets in college. The best part of this particular pamphlet is a Checklist in Case of Trouble. Every possible stitching scenario is covered.
At the top of the list for skipped stitches was Wrong size or type of needle for the fabric. But I skipped that because I assumed I had the right type and size of needle. Other solutions suggested:
Timing of machine - check
Lint - check
Threading - check
Damaged needle - check
Sewing at a steady, even pace - check
Fabric with excess finish - ? possibly
Hold fabric taut while sewing - check
Nothing seemed to make a difference. I think the excess fabric finish contributed to the problem, but was not the root cause. Stitching on other fabrics showed the problem still existed. So I finally decided to cave and try the next needle size up. It couldn't be that simple, but why not try.
In a true, head smacking moment, the machine stitched absolutely perfect on both grains. And it makes sense too. A larger size needle is stronger and can pull the yarns of the fabric apart easier. Since I have to stitch through two layers of flannel, a larger size needle is necessary. Now I have to decide what to do with 100 size 12 130x3 needles, while I wait for an order of size 14 needles.
One thing I am not sure about. I had some Singer brand size 14, 130x3's laying around loose in the table drawer, which work great. The Singer brands are known to be the best, but also the most expensive. I am ordering the Organ brand (which is what my size 12's are) in the size 14. Hopefully, there isn't too much of a quality difference.