Improving my twin needle hems

singer_357_twin
The twin needle threaded up and ready to go.

I don’t have a coverstitch machine (yet…), so my favourite way to hem knitted garments is with a twin needle on my regular sewing machine. I’ve been sewing lots of knits over the last year (children’s clothes 1, 2 and 3 as well as things for me 1, 2 and 3). And I’m not very happy with my twin needle hems so I thought I’d scout around the blogosphere for some tips, test them, and share the results with you all.

So here’s my control example: some sweatshirting fabric scraps sewn with a twin needle, using Gutermann sew-all thread on top and bottom, medium presser foot pressure and the ordinary tension settings.

As you can see, the two lines of stitching on the top are fine, but there’s not much zig and zag in the black bobbin thread meaning them hem won’t stretch much. Fine in a loose fitting sweatshirt, maybe, but not great for a tight-fitting T-shirt. And when you look at the hem in profile, it’s got that tunnelling effect where the fabric between the two lines of stitching almost looks as though it has piping inside it.

The first tip I found was to adjust the tension on the top thread. Cranking up the tension on the top should make the bobbin tension lower and create more zig and zag in the bobbin thread. Except it didn’t, so I haven’t taken any pictures of that. The only thing it did do was to stop the hem from curving – almost as if I’d adjusted a non-existent differential feed.

Woolly nylon in the bobbin thread

The second tip I found was to try woolly nylon thread in the bobbin, instead of sew-all. This stuff is weird! It’s fuzzy, stretchy and feels very, very synthetic – a bit like you’ve unravelled your tights, I suppose.

woolly_nylon

With woolly nylon in the bobbin, the hem comes out like this:

I think there’s a bit more zigzagging going on in the bobbin thread – although it’s hard to see with the pale grey colour I bought (sorry!), but there’s still a definite tunnel effect when you look at the hem in profile. So far, no better.

Lowering the bobbin tension (while using woolly nylon)

Next up, I tried lowering the bobbin tension as suggested on Oliver and S. My sewing machine manual doesn’t even tell me how to do this, as Janome firmly believes you should only ever need to alter the top tension to get the right balance. (If you try this at home, please make sure you know how to undo it, too.) To save my sanity if I couldn’t undo it, I followed Rachel’s example in the Oliver and S post and bought a second bobbin casing to play with, loosening the screw to lower the tension.

The results looked like this:

Lots more zigzagging in the bobbin thread, which means the hem is much stretchier. But I’ve still got the tunnelling. Aaargh.

Have you solved this problem? What should I try next?