The Upholstery Forum

Am I doing something wrong during my top stitch that I end up seeing the seam stich thread in the middle?

It may or may not matter but I keep my seam stitches smaller than the open stitches. Looks like you top stitches are tight enough so I would suspect your seam stitches are the same. On my machine seam stitches are on 4mm and the top may be 6 to 7mm.
Hopefully others will chime in.

@LLeeT Yes I do the same. I Usually use a thicker thread on the French seam .

So my seam is 6 and the top is 8. I used the same thread for both, would it be better if I used a smaller thread for the seam?

make sure to do relief cuts on the curves and corners don't force it or hold it tighter , cause that will cause your stitches look different and not even.

Smaller thread will be not as strong. Tighten up your seam stitches, along with Ronda's advice.

I should have said SHORTEN instead of tighten.

I use a shorter stitch (6mm) when joining panels and longer (10mm) for topstitching. Also try reducing the side pressure from your hand at the foot when topstitching ….. hope that makes sense.

Dunno much about upholstery yet, I've been doing boat canvas, so this is definitely an upholstery newbie question. So for every topstich I have ever seen and done, the two pieces of seam allowance are moved to one side and topstiched together - never split / pulled to each side like in Jsykes pictures, with TWO top stitches. I can't think of any benefit to splitting the seam allowance to make two top stitches ... maybe sometimes it can look cool ?? Often my stitching lines are a little wiggly - that wouldn't look cool at all. So much to learn, where can I learn more about this double topstiching to make me think it is a good idea?

Jsykes, FWIW, boat canvas is usually under a lot of tension anyway, more so when it is windy, so I always pull the canvas tight laterally when I topstich so one stitch line isn't getting more tension than the other when the canvas is installed, so what you call the "seam stitch thread" is also always visible for my canvas, as well as on the canvas of the many repairs that I do.

Unless you using a a binding tape, double top stitches are only decoration. The binding tape goes on the back side with the seam allowance folded to each side of the main stitch. When you sew both open stitches, you sew though 3 pieces of material, thus making a stronger seam. If you fold both seam allowances on one side of the main stitch, it also makes your main stitch stronger. I hope that is a little better than mud to you.