Sewing knit jersey material on a vintage straight stitch sewing machine - Setting up a vibrating shuttle machine for sewing knit fabrics
Lighten up, it isn’t difficult.
Sewing knit jersey material on a vintage straight stitch sewing machine - Table of Contents
As detailed in my last blog post, the main difficulty in sewing knit fabrics with a straight stitch sewing machine lies in getting the tension set properly.
You will need to make some adjustments to be able to sew knit fabrics on your vibrating shuttle machine. You will also need to use jersey (ball point) needles.
| What you need |
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- Jersey (ball point) needles are a must, even if you were to use a zig-zag or overlocker. Normal needles (sharps) can cut threads in the cloth. The ball point needles push the threads of the fabric aside so as not to damage the cloth.
- A scale to adjust the thread tension.
The first thing to do is adjust the presser foot pressure so that the fabric feeds properly.
| Presser foot pressure |
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Tighten the indicated knob for more pressure, loosen it for less pressure.
- Get a scrap of fabric a couple of inches wide and about as long as the longest seam you expect in your project.
- Fold the cloth in half the long way so that it is about 1 inch wide. Line up the ends.
- Remove the upper thread and shuttle from the machine.
- Put the strip under the presser foot with the end behind the foot, and lower the foot.
- Hand crank the machine or run it at very low speed with the electric motor.
- The strip of fabric should feed straight, and the edges should stay matched.
- Most importantly, the ends should stay matched.
- Run the whole strip through.
- When you get to the end, the the strip should still be straight and the ends should still be lined up.
- If the ends are not lined up, reduce the presser foot pressure.
- If the fabric doesn’t feed, increase the presser foot pressure.
- Repeat this process until the fabric feeds and the top layer and the bottom layer stay aligned.
Now adjust the shuttle and the upper tension to 15 grams. Follow the hints here for adjusting the tension on a vibrating shuttle machine and here for general tips to adjusting thread tension using a postage scale.
You also need to use the shortest possible stitch length. As crazy as it sounds, more stitches per inch means more stretch. The lowest you can go is usually about the thickness of the needle.
| Fine stitches |
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To meaure the stitch length, I “sewed” a piece of paper without thread. As you can see, the holes are spaced just a tad further apart than the size of the holes themselves. I probably could have made the stitches a bit finer, but it worked out OK.
With the Kayser L adjusted to 15 grams thread tension (upper and lower) and the presser foot pressure adjusted (and the stitch length shortened,) I ran a simple experiment.
I used three strips cut from an old T-shirt to compare the “stretchiness” of unsewn cloth with the “stretchiness” of cloth sewn with different tension settings.
| Test strips |
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The strips are all about 30 centimeters long (12 inches) and were originally 5 centimeters wide (2 inches.)
The plain strip stretched best:
| Plain strip |
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I could stretch it from 30 to about 38 centimeters. It didn’t protest or pop, though it was difficult to hold stretched that far.
The other two strips weren’t quite as stretchy after sewing:
| Sewn strips |
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Both can be stretched to about 36 centimeters. That’s a couple of centimeters short of the unsewn strip.
The strip sewn with 35 grams of thread tension actually started out a bit longer than the other strips, so it didn’t really stretch quite as far as the strip sewn with 15 grams of tension.
So far, that doesn’t sound like there’s an advantage to the lower tension.
The difference is that when I stretched the 35 gram strip, the seam popped. The thread broke in there somewhere. If that were in a piece of clothing, it’d be waiting for a chance to pop and fall apart sometime when you least expect it.
I tried my best to make the 15 gram strip pop. I went so far as to grab it in both fists and put my back into it. It didn’t stretch any further, but it didn’t pop, either.
The lowered thread tension lets the fabric and the thread move enough that the seam holds despite some really rough handling.
Summary:
- Use the lowest practical thread tension (15 grams or lower.)
- Adjust the presser foot pressure for proper feed.
- Use the shortest practical stitch length (approximately the thickness of the needle between the stitches.)
- Use jersey (ball point) needles.
The killer is number 1. Only vibrating shuttle and transverse shuttle machines can work reliably at the low thread tension required to successfully sew knit fabrics.
By the way:
You don’t need a special “stretch thread” for this. I used plain polyester thread that has practically no give.
Sewing knit jersey material on a vintage straight stitch sewing machine - Table of Contents