Sewing machine help

[Aparecium]

Something is wrong. Tension?

The 'dotted' line of stitches is the front. The 'solid' line of stitches is the bobbin thread on the back. It does not look right.

Any ideas?

(What looks like a jump in the bobbin thread is where I started unpicking, before taking the photo to ask for advice here.)

It looks as if the tension on your bobbin needs tightening.
First, check that both threads are threaded correctly.

I rethreaded, but it made no difference.

The next project I did was freehand machine embroidery using a purple top thread and black bobbin thread, on black fabric. The photo shows the reverse. You can see that the top and bobbin threads are much better balanced on this, with only occasional spots where the top thread comes through. Mostly where I have changed direction at the end of a line.

I hadn't done anything to the bobbin case, just switched bobbins. Top thread same weight as before, black bobbin thread bobbin-weight.

I often switch between bobbin-weight thread and top thread weight in the bobbin, and have never needed to adjust the bobbin tension. I'm really wary of messing with it! It's the only bobbin case I have.

Do you change your needles regularly and use the right needle type for the fabric you’re sewing?

Altering the bobbin tension is one of the last things I’d try, rather than the beginning of the list.

I used the same needle for both projects. The standard needle IYSWIM, 80/12 I think? Not brand new, but recently replaced. The black fabric is heavier than the floral fabric.

It’s not just size but type of needle that you have to consider. Also, buy decent brand needles and thread. The stuff from Lidl etc. isn’t great quality.

I use mostly Gütermann or Coates threads and Schmetz or Organ needles.

The Schmetz Needle App provides some good advice on choice of needle.

Also, as a general rule, if the thread on top of the fabric is the problem, then it could be the bobbin thread. If it’s the underneath that’s the problem, then it’s your top thread.

Is your machine due a service? One of my machines loves to be oiled a lot.

Maybe you could post a short video of it working so we can see the threading and hear it running?

Sounds silly but have you threaded the machine properly. Mostly when I have stuff like that I haven't threaded the top thread properly (needle down and not up). I'd redo the bobbin (re make it) and rethread everything and then try with a simple piece of cotton and see how you are then

Needles: Schmetz, standard pointed (ie not jersey ball tip etc)
Threads: Gutterman
Serviced: 2021, though not heavily used and I dismantle, clean and oil the whole area under the footplate after every project.

I don't understand about threading with the needle down. How is that possible? I always thread with the needle up - which is the default position for my machine.

Also, as a general rule, if the thread on top of the fabric is the problem, then it could be the bobbin thread. If it’s the underneath that’s the problem, then it’s your top thread.

I suspect this is it, and that adjusting the top tension would help. I rarely need to adjust the tension on this machine. I'm just surprised at the difference between the results in the two different fabrics.

I meant needle slightly down rather than fully down of course! When I've manually turned it and then not pressed needle up and not lifted the presser foot.
I personally always use the same thread top and bottom so if you are using different then you may well need to adjust tension. Just play around with it?