Updated: Jan 30
Getting nice, even and secure stitches mostly depends on your tension settings, although bad quality thread and improper threading of the machine can sometimes be responsible for bad stitches and frequently breaking thread.
First let's make sure your Tension is right. If you have a modern table top machine or a computerised machine as above, you don't have to worry much about this, just leave everything on the default setting. But if you have an old-style treadle machine or an industrial, then you might want to set your tension with this guide. As always read your user manual first.
Thread your machine following your user manual preferably with different coloured threads so that you can better see the upper and bobbin threads
With your presser foot UP, pull your upper thread just a little, it should move freely with slight resistance, because the tension discs are open when the presser foot is up. If the thread is too free, tighten your tension screw (Turn to the right or to a higher number), if it is too hard to pull, loosen your tension screw (Turn to the left or to a lower number).
When your presser foot is DOWN, the thread should be hard to pull, because the tension discs are closed.
The same test applies for the lower or bobbin thread. The tension can be adjusted by tightening or loosening the little screw on the bobbin case. BUT this is not usually necessary. Sew a test fabric before fiddling with the bobbin tension.
Testing your Tension
Set you Stitch Length to 2.5mm or 10spi depending on your machine type
Stitch width should be on 0, if you have a zig-zag machine
Put a scrap piece of fabric under the presser foot, lower your presser foot, turn your handwheel towards yourself to lower your needle into the fabric
Now step on your presser foot gently and sew a few stitches. Try to go slowly
Your stitches should be flat and even on both sides of the fabric and should be hard to pull out. These are supposed to be permanent stitches.
If you have any knots under the fabric. Re-thread your machine again.
If you get tangles or loops under the fabric, the stitches are too loose, and you tighten your upper thread tension by turning the tension knob to the right
If you can see the bobbin thread on the upper side of the fabric, the stitches are too tight and the fabric is puckering, loosen your upper thread tension by turning the tension knob to the left
If your thread is breaking a lot, loosen you upper thread tension
For more details on tension settings, please refer to the following resources
1. Your User Manual if you have one
Depending on the model of your sewing machine, you may have one setting for stitch length and another for stitch width. If you have a straight stitch only machine, you will only have a dial for stitch length.
Stitch length setting comes in two ways, Stitches per Inch (SPI) or in Millimetres.
The default length of a stitch is 10 SPI or 2.5 mm. These two settings mean the same thing. Let's say approximately
1 inch = 2.5cm or 25mm
Therefore if a stitch is 2.5mm long, there will be 10 stitches in an inch. Specifically
________________________ = 10SPI
2.5mm (stitch length)
You don't really need to know all the math involved, but that's just what the dials mean.
Now if your machine has numbers 1 to 4, or 1 to 5, these are most likely millimetres. So 1 will be the shortest and tightest stitch setting, while 4 or 5 will be the longest and loosest stitch settings
On the other hand, if your machine has numbers 6 to 30. these are most likely SPI, with 6 being the longest and loosest stitch, and 30 being the shortest and tightest stitch.
Stitch width setting only comes in machines that do zig-zag or other decorative stitches. The numbers are in millimetres and simply tell you how wide or narrow your stitch will be, with 1.5 being the smallest and 5 or 7 being the biggest. Note that some zigzag machines do not have a stitch width dial, so you can't adjust the stitch size.
The combination of the stitch length and stitch width settings can produce different styles of zigzags or other decorative stitches.
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