It can’t be that hard, can it?

Sewing knit jersey material on a vintage straight stitch sewing machine - Table of Contents

If you ever ask about sewing jersey knit materials at home on a sewing machine, you will hear a lot of stuff about how you need an overlocker or that you can get by with a zig-zag machine. You will also hear that it can’t be done on an old fashioned straight stitch sewing machine.

Such “words of wisdom” are mostly correct. It is easiest if you have an overlocker - they are made for such tasks. If you have a zig-zag machine, you can use a light zig-zag to get a stretch effect. Many zig-zags even have a special “stretch” stitch that’s supposedly even better. Folks that use straight stitch machines, though, will be hard pressed to find a reliable way to sew jersey. There’s lots of suggested ways, but nothing that really inspires confidence.

There’s two main problems in sewing knit materials:

  1. Stretch. You need a stitch that can stretch with the fabric.
  2. Feed pressure. You need enough pressure on the feed dogs to move the material, but not so much that the feed dogs stretch the material while sewing.

That second point is mostly pretty straight forward with vintage sewing machines. There’s usually a knob that you can twist to adjust the pressure on the feed dogs.

The hard thing to deal with is the stretch. Overlockers and zig-zags get around it by using more thread per stitch. The offset ends of the zig-zag stitch mean that there’s more thread than just the simple length for a given number of stitches per inch.

Vintage straight stitch machines can’t do that.

What works instead of that is to use a stupidly low thread tension.

A zig-zag stitch on knit materials puts the extra thread length needed of the stretch on top of the material.

A really low thread tension leaves “extra” thread in the stitch itself - that’s vertically instead of horizontally when the material is under the sewing machine needle.

A high tension pulls the threads tight into the material, removing the thread needed for the stretch.

A low tension allows the thread to lay loosely on the cloth.

The result is a stitch that gives as much as an overlock or zig-zag stitch, but that is straight.

The catch is that damned few sewing machines can operate with a thread tension low enough to make a stretchy stitch.

Most machines depend on the upper thread tension when pulling the upper thread around the shuttle to make the lock stitch. Since it takes a fair amount of tension to pull the thread around the shuttle, you have a lower limit for the thread tension.

On most machines (oscillating hook like the Singer 15 and derivatives or rotary hook machines like the 66 or 201,) the lower limit for the thread tension is more than 25 grams (1 ounce.) There’s nothing to stop you from adjusting the upper and lower tension to less than that, but it won’t do you any good. When the tension is too low, the take up lever simply can’t pull the upper thread thread around the bobbin case - you get great long loops on the bottom side.

Vibrating shuttle machines are different, however. On such machines, the thread is pulled around the shuttle by the motion of the shuttle. The shuttle pulls the thread sideways against the friction of the thread on the eye of the needle. The upper and lower thread tension are really only involved in locking the stitch, not in pulling the thread.

If you have a vibrating shuttle sewing machine, then you can sew stretchy knit material with ease.

Since I happen to have a Kayser model L vibrating shuttle sewing machine here for some work, I thought I’d try it out and document what you have to do to sew knit fabrics on a vibrating shuttle.

The next couple of posts will tell how to do it and show an example sewing knit T-shirt fabric on a vibrating shuttle sewing machine.

I first heard about this particular trick while watching a TV movie.

Die Herbstzeitlosen (In English, Late Bloomers) is a Swiss movie about some older women in a small Swiss village who set out to accomplish things that they hadn’t been able to to when they were younger.

One of the women was a seamstress, who had dreamed of opening a lingerie shop in Paris, making and selling the things herself. He husband dies, and she decides to fulfill her dream - not in Paris, but in the shop her husband had owned in the village.

At one point, she mentions buying an old sewing machine because she could use it to sew fine seams that will stretch in the fine fabric of the garments she wants to make. The machine itself is shown briefly. I didn’t know the difference back then, but from my memory it was either a transverse shuttle machine or a vibrating shuttle machine. I haven’t been able to locate a copy of the film to verify it, so I may be remembering it wrong. I know that at one point she uses what appears to be a relative of the Elna Grasshopper.

While researching something or other for the Pfaff model K I fixed up a while back, I came across this blog post by a hobby seamstress who used a Stoewer vibrating shuttle machine to sew nanotex jersey that had given her trouble on a zig-zag machine.

With two such stories and a freshly renovated Kayser model L vibrating shuttle machine in hand, I decided I’d have to try it out and see for myself.

Sewing knit jersey material on a vintage straight stitch sewing machine - Table of Contents