This post is probably of most interest to new and newish sewers.
There are a few basic things I would like to say about sewing machines. It is helpful to know a little something about how they work to help you get through the take a deep breath part of sewing.
At home I have some original patent applications for sewing machines dating to before WWI. Someone found them in an old drawer and asked if I was interested in having them.
I said yes.
What is fascinating about these patent drawings is that essentially the technology for forming the important lock stitch in a standard sewing machine is the same as it was then, as it was in the mid 1880s in fact when Isaac Singer bought the idea from someone none of us remember for $50.00
The thing to know is that each tiny stitch on your sewing machine is in fact a miniature knot formed when a precisely measured top thread intersects and slips through the loop of an equally carefully measured thread delivered up from below in the bobbin area. This knot idea was huge. It liberated seaming from the chain stitches that could be easily pulled out, and explains why we all have to spend so much slow time with a seam ripper.
Back to the process of stitch formation.
The thread length necessary to form the top part of the thread is measured by the movement of the “take-up” lever which is that arm thing that goes up and down above the needle. The thread length necessary to meet it is measured in the bobbin area with each rotation of the bobbin. It is worth saying here too that a neatly wound bobbin, and one wound not too fast so the thread if it is polyester will stretch in winding and then retract in sewing, will give the machine a better chance of delivering a nice even stitch.
The whole thing, a beautiful stitch, depends on the precision of these two threads meeting when the needle takes the upper thread down to pass through the loop below and brings it up again to the surface.
So a good stitch depends on making sure all elements can do this as accurately as possible.
This is why the needle point is so important – that one tiny surface has to go through the fabric as the delivery agent.
So often sewers blame weirdness on the machine that is in fact a wrong needle problem.
The most frequent manifestation of this is “skipped stitches” – a term that refers to a nice little series of stitches randomly interrupted by a couple of long loose stitches.
When this happens it just means the needle was not able to make the proper connection down below through the fabric due to piercing issues.
You see this most often in knits sewn with a sharp or universal needle – essentially the needle keeps bouncing along until it can get through. In this case changing to a ballpoint needle that spreads, rather than tries to puncture the fabric, will solve the problem. In some fabrics, those with a lot of synthetic in them the needle can build up some static too, and the same thing happens. At those times I usually try to sew a couple a bit through a Bounce sheet to cut the static.
There are other things that can affect stitch quality.
How the thread has been threaded through the upper track is a big one. In fact so many of what may appear to be bottom issues – the notorious “bird’s nest” when the top of the stitch looks great but the bottom is a mess of loopy threads – are actually nearly always upper threading issues. Primarily these occur because the thread is not in the right places, out of order (machines are always threaded through the tension disks and then through the take-up levers), or not nestled securely between the tension disks.
The quick fixes here are to pull the thread out of the top and rethread, hoping you get it right this time, or making sure you thread the machine with the presser foot up, there is a reason for this.
Don’t be afraid of your tension dial by the way.
Essentially tension mechanisms in machines are variations on two Barbie dinner plates pushed close to each other with springs. When the presser foot is up the plates are wider apart so you can get the thread between them. When the presser foot is down the plates move closer so they can get a good grip on the thread and control the quantity delivered to the take-up lever for measuring. Sometimes if you thread quickly with the presser foot down, or make a threading mistake, the tension mechanism is by passed and essentially you have thread going through the machine with about as much control as if you threw a rope out of a window.
All that excess thread just gets dumped by the needle below and that’s why you get a bird’s nest.
There are of course times when you want to loosen the upper tension a bit – for example when doing a satin stitch or a buttonhole you want there to be a bit more top thread than bottom so the lock stitch gets pulled to the underside and the top bars of thread look nice and smooth. Some machines even have a “buttonhole setting” on the tension dial that tells you where to put the tension to do this, just have to move it back to normal for construction sewing.
A balanced tension, where the lock stitch meets in the middle of the fabric, makes the strongest stitch. Of course it is hard to see if the lock stitch is situated where it should be in a thin fabric, which is why many dealers use thicker fabric like twills to demo a machine on, it will always make the stitch look nicer.
The upper tension is controlled by the dial at the top, to the right of the take-up lever, and the lower tension, which controls the rate at which the bobbin thread leaves the bobbin, is controlled in many cases by a tiny screw that tightens or loosens a metal part that lays over the thread slot in the bobbin case. Check your manual for specifics.
Incidentally because it can be so hard to see if your top and bottom tensions are balanced in a straight stitch most technicians test for this with a zig zag. This is often why there will be a both a straight and zig zag sample left under the presser foot on demo fabric after a service – that is there to demonstrate you now have balanced tension.
A word too about straight stitches that look slightly like they are diagonal rather than in a perfect straight line.
Older sewers in particular are famous for complaining about this in their “new” machine which they so often pack away to bring out the old workhorse, the one with the nicer stitch.
This diagonal stitch issue is largely a result of the wider opening in the throat plate (translated the hole in the metal part under the presser foot so the needle can go down) that is needed to accommodate the swing in the needle of wider zig zag and other sideways stitches.
This wide opening creates some insecurity in the area the presser foot is trying to keep still for all the stitch action and this wobbling creates that distinct slightly diagonal stitch. You don’t see this in old straight stitch only machines, less in machines that do only a 4 mm. zig zag and can be quite visible in machines that do zig zags of 9 mm. or more.
You can counter this by creating a more secure and stable stitching area by:
· Replacing your zig zag throat plate with a straight stitch plate – one that has only a very small opening to accommodate the needle and allows for zero side to side swings. Some machines, vintage in particular, come with this plate, most machines have them as optional additional accessories. A straight stitch plate is a primo addition if you want impeccable top stitching or do a lot of sewing of fine fabrics like chiffon (you must be crazy) that tend to get pushed down into the bobbin area even when you do all the usual things like start your seams ¼” in from the raw edge so the first stitch has fabric all around it.
· Moving your needle as far as you can to the right or left, essentially eliminating one side of the open area. If you were wondering why your machine has a straight stitch with a left and/or right automatic setting this is why btw – for better top stitching.
Wow this is a lot of detail on small issues. Hopefully though if you are a new sewer, some of this has been helpful.