Sewing Machine Mechanics and Stitches

Hello Everyone,

I’ve had a couple of people write and ask me what Chris (another sewing machine mechanic) and I were talking about in the comments. So here is some more information to help clarify that discussion for the non-mechanics ๐Ÿ™‚

The first question was about the top thread looping or “bubbling” on a wide zig-zag. A typical stitch for a mechanic to sew is a 4X4 zig-zag to check tension balance. This should result in a nice top stitch and a dot of top thread on each side of the bottom of the stitch.





As you can see from the two sewing samples above, the top stitch on the right is loose… “bubble” looking. Yet you can see from the bottom stitch on the left that the stitch is in balance on tension. So the question is, what causes this “bubble”? The answer is, the wrong presser foot. We generally use a “regular” foot when working on sewing machines. But most sewing machine manufacturers have a variety of feet for their machines. Each foot has a specific purpose such as a cording foot, a button hole foot, a zipper foot, and the one to correct this “bubble”… the open toe embroidery foot.

As you can see from the image on the left, the stitch sewn with the “regular” foot has a loose bubble on the top of the fabric. That is because as the fabric is being fed under the presser foot, the thread is pinched between the foot and the fabric. The stitch on the right was sewn with an “open toe” foot. So those stitches lay flat on the fabric, because the next stitch goes down before the thread reaches the presser foot.

The second thing we were discussing (and I get this question from a lot of you) is why there is a thread tail on the underside of a wide (5mm – 9mm) zig-zag, or blanket, or hemming stitch. The answer is, because until the last few years, sewing machines were never intended to sew such a stitch.

When you look at the two zig-zag stitches on the right, notice that the tail from the top thread is longer on the left than on the right. The machine left the factory that way. It has a wide stitch width, not so it can sew a wide zig-zag, but so it can sew a wide decorative stitch. That decorative stitch will have several fabric penetrations before it makes it from the left side of the 9mm to the right side of the 9mm stitch width. This will minimize the amount of pull on the left side of the stitch. The closer the two stitches are on that side, the less pull there will be on the top thread. The straight stitch on the right is with the needle in the full left position, and it is balanced. So it is not where the needle penetrates the fabric, but where the previous penetration and next penetration will be in the fabric. Some new high end machines can adjust the top tension for every needle penetration in a stitch, thus virtually eliminating that thread tail on the bottom of a wide stitch.

I hope that all made sense. ๐Ÿ™‚

May Your Thread Never Break!



Needles are what makes a sewing machine sew!

I have answered thousands of questions about needles. Sometimes I was asked about needles. Sometimes I was asked about a problem where the answer was the needle. The topic is more than just the right needle for the job, or the right size needle for your project and your thread. The fastest, easiest, and cheapest tune-up you can give any sewing machine, quilting machine, overlock machine (serger), cover-stitch machine, or embroidery machine is a new needle!

This will be a long blog post and it won’t cover which needle to use for which project (but I will provide a link). People think that if it still makes a stitch, there is no need to replace a needle.ย I have over the years had many sewing machine owners (and one quilt machine owner) bring me their machine after years (sometimes decades) and tell me that it still has the original needle. So if you can hear the needle penetrate the fabric, it is either dull, bent, or the wrong needle for your project. As I said in the opening, the fastest, easiest, and cheapest tune-up you can give your sewing machine is a new needle. So if you have started to skip stitches, fray thread, break thread, pull fabric, or your stitch quality is simply starting to deteriorate, change your needle!

Needle manufacturers have spent millions of dollars developing and perfecting their sewing machine needles. If you use Groz-Beckert, Organ, or Schmetz needles, you are using needles that rarely have flaws. I am not saying or suggesting these are the only quality needle manufacturers, but I am saying if you buy from one of them, you have a quality needle. I also like Klasse’ for overlocker machines. I am also saying it IS POSSIBLE to get a bad new needle. If the new needle has a problem, try another. If both new needles have a problem, it is most likely the machine or the needle type and size you have chosen.

Needle Systems. – There are dozens of needle systems for different types of machines. For most home sewing machines over the past 60 years, the 705 needle system is what makes the machine sew. The 705H is by far the most common household sewing machine needle (sometimes shown as a 15 x 1), but 705B are still on the bench of almost every sewing machine mechanic. When I have a machine on the bench that took a 705B needle (like the Bernina 500, 700, and 800 series – the OLD ones), if it comes in with a 705H needle, I will adjust the needle hook clearance so that it no longer takes a 705B needle. The difference between these two needle systems is that the 705B grows to the front of the needle as it goes up in size. The 705H needle grows equally as it goes up in size and the scarf becomes deeper to accommodate the larger needle size. In this post we will not discuss the systems for industrial machines or quilting machines or overlocker machines or cover- stitch machines or multi-needle embroidery machines. Today we will discuss needles for home sewing machines. I will write separate posts for quilting machines and overlock – cover-stitch machines. The commercial embroidery industry has an abundance of information about needles for multi-needle embroidery machines.

How They Work. – I put this in a previous post, but I’ll repeat it. When you look at your sewing machine needle, you will notice the front has a groove and the back has a small notch (called the scarf) above the eye of the needle. So when the needle penetrates the fabric, the thread slides in the groove. When the needle starts to rise, the thread will still slide in the groove, but since there is no groove on the back, the thread drags on the fabric and this creates a small loop. The hook comes into the scarf (the notch) on the back of the needle and picks up this loop. It then carries the thread across the face of the bobbin case and wraps it around the bobbin thread creating a knot – a stitch.

Needle Sizing Problems. – First, needle sizes are Metric and Singer. In the metric system, a size 100 needle is 1 mm. So a size 80 is .8 mm and and a size 65 is .65 mm. The other number (like 65/9 or 80/12) is the Singer size. It is obsolete, but it sticks around like an old bumper sticker. It fades, but it just never goes away. So a Singer size 1 is a metric .2 mm needle. So that would be a 20/1 needle. It goes up by 1 for each .05 mm. Now you you know another useless fact about Singer needle sizes :-).

The first problem I see (too often) with small needle sizes relates to needle threaders. Most manufacturers today use some type of automatic or semi-automatic needle threader. But the hook on the threader that goes through the eye of the needle and grabs the thread has a size. If the eye of the needle is too small, it is not going to make a new hole in the needle. It might, however, put a burr in the eye of the needle you have already installed. Most will not fit through a needle smaller than a size 75/11 needle. (I know you are all doing the Singer needle size math now. It’s okay, have fun with it until you get bored with adding up parts of millimeters) So if you are using a size 70/10 or a size 65/9 and you try to use your threader, you bend the hook. Sometimes this can be fixed, sometimes you are out $10, or $20, or $30, or even the fun ones in the $49 range plus the labor to install it on your sewing machine. So look in your manual. I really don’t know of any sewing machines that will thread a size 70 needle. If you do, please add it to the comments.

Thread to Needle Ratio. We talked about how needles work with the groove and scarf and the loop and hook. If the thread is too large to slide in the groove on the front of the needle, you end up with a loop on both sides of the needle. Result is skipped stitches, loose stitches, or frayed thread. If the needle is too large for the size of the thread, it does not drag on the fabric to create a loop. This results in loose stitches or skipped stitches. So when using a heavier thread (30 weight or top stitch or “heavy duty”), use a larger needle. When using a 50 or 60 weight thread, use a smaller needle.

Changing Needle Problems. – So when you change needles, make sure they are inserted all the way. Frayed thread, skipped stitches, or not being able to bring up the bobbin thread after changing needles are good indications that you did not put the needle all the way up. If that little notch (the scarf) on the back of the needle is too low, so is the loop that the hook is suppose to pick up from the needle. So now the hook hits the thread and frays it, or misses it and skips a stitch. If you put the needle in backwards (usually on older machines like the Singer 221 Featherweight), the loop is on the wrong side and so you can’t bring up the bobbin thread and it skips more stitches than it will make.

Needle Types. – For almost every project there is a needle designed to be efficient at that work. When you are disposing of old needles, I suggest a medicine bottle with a hole in the lid. (you can use these later for putting things on cork board or the wall). The most common needle out there is the universal needle. There are also Double Eye Needles, Embroidery Needles, Hemstitch (wing) Needles, Jeans Needles, Leather Needles, Metallic Needles, Microtex (sharp) Needles, Quilting Needles, Spring Needles, and Topstitch Needles. Here is a link to the different types of needles and how they are used. Click Here for Needle Brochure.ย 

Bent Needles. – A full ten percent of all machines that come to my bench have a bent needle. This accounts for most of the skipped stitches and broken thread machines I see. When you look at the needles on the left, some are very obvious. But ALL of those needles are bent. If you had a bird nest in the hook area, if you hit a pin, hit a “hard” seam, hit the needle plate (that’s for those of you who pull the fabric, and you know who you are), or tried to pull the fabric out with the take up lever not fully raised, you may very well have a bent needle. Symptoms of a bent needle? Skipped stitches, frayed thread, broken thread, and of course – broken needle (problem solved – but new problems follow many broken needles).

Thread and Needles. – The image on the left shows how many stitches are made before a piece of thread actually gets onto the fabric. So on this machine, the thread passes through the eye of the needle 42 times before it actually makes a stitch on the fabric. Press here to watch the video. ย 

Most people don’t realize that the thread passes through the eye of the needle several times before it makes it to the fabric as a stitch. Cheap thread, old thread, thread that is too large for the needle, and a bad needle eye will cause thread worms (frays that push up from the needle like a woolly worm), frayed thread, broken thread and broken needles. If your project is worth making, it is worth good thread! But even good thread has a shelf life. So if you remember you have that color thread from a project you did for the 1976 Bi-Centennial, you may have problems using it today. Since the thread must pass through the eye of the needle multiple times in each direction, broken thread may be a challenge. Easy way to figure out if it is the thread or the needle is to change the needle or try another spool of good thread.

I hope today’s discussion about sewing machine needles was helpful. If you have questions or comments, please use the comment link on the left side at the top of this article. If you need needles, you can click here.

May Your Thread Never Break!

Mike Roussin

Why are my sewing machine stitches slanted?

Happy New Year Everyone! I hope 2017 brings you health, happiness, and everything else your heart desires.

Today we are going to discuss a topic that comes up often. People with embroidery machines never ask me this question. But seamstresses will sometimes ask and quilters will often ask why their sewing machine is giving them a slanted stitch? Here is what they are asking about.

They are wondering why their “straight stitch” is slanted instead of straight. They all assume the machine is out of adjustment, but that is not why the stitches are slanted. Here are the two basic types of sewing machines.

The machine on the left (Bernina 630) has an oscillating hook. The machine on the right (Bernina 185) has a rotating hook. Machines with drop in bobbins are also rotary hook machines. Over time we will be discussing each hook type in depth, but for today I just want you to understand that it makes no difference what type of machine you have it will still sew a slanted stitch.

Here is why, the way a stitch is made. When you look at your sewing machine needle, you will notice the front has a groove and the back has a small notch above the eye of the needle. So when the needle penetrates the fabric, the thread slides in the groove. When the needle starts to rise, the thread will still slide in the groove, but since there is no groove on the back, the thread drags on the fabric and this creates a small loop. The hook picks up this loop and carries the thread past the bottom of the hook path where the thread is no longer held by the hook.



You can see the hook tips above are just past the bottom of their cycle. The thread loop they picked up from the back of the needle (the green thread) is dragged across the face of the bobbin case. In the position you see above, the thread is released from the hook and the take up lever pulls the thread up. This wraps the top thread around the bobbin thread creating a knot, or stitch.

So why are the stitches slanted? Because, the hook picked up the thread on one side of the needle and released it on the other side of the needle. So the thread enters the hole made by the needle on the side of the bobbin thread where it was picked up and leaves the hole on the other side of the needle and bobbin thread. ย The bigger the needle, the more obvious this will be to the naked eye.

The arrows show the direction of sewing. The top pink stitches were made with a size 75/11 needle. The middle two purple stitches were made with a size 80/12 needle. The bottom two brown were made with a size 90/14 needle. We will discuss the different needle types and sizes in the future, but for now I just want you to be able to observe that as the needle size grows, the slant of the stitch becomes more obvious. That is because the needle is making a bigger hole in the fabric so it is easier to see which side of the hole the thread went in and which side of the hole the thread comes out.

This “straight” stitch will become much straighter when the fabric is washed. But when you are observing that straight stitches are actually slanted, there is nothing wrong with your machine…. or you. So don’t stress out over slanted stitches. Just shows your sewing machine and your quilting or seamstress work are bordering on perfect!

I try to write this blog to address questions and problems I see over and over. I hope this article was helpful. Please feel free to leave me a comment or question. The comment link is at the left of the top of this article. Again, Happy New Year! ๐Ÿ™‚

May Your Thread Never Break!

Michael Roussin