Skipped stitches with stretch knit fabric

[Gymnast]

The problem is skipped stitches.

I got a job to sew some patches on a heavy stretch knit fabric used for cover on some gymnastics mats. I currently use a domestic Singer 237 and zig zag stitching with a V69 polyester thread and a 100/16 universal point needle. Zig zag is used to allow stretch of the seam.

It seems like the stretch fabric couse a smaller loop to be catched by the hook. I have tried to adjust the distance between hook and needle to a minimum, and it did help, but I do like to have a little distance here for normal use.

Can you adwise some change for me, to make it easier for the machine to sew this kind of fabric? Is another machine better for this?

[Wizcrafts]

Try to increase the slack thread using the check spring adjuster, There are three adjustments available, depending on what type of check spring system your machine has. The style with the most adjustments has the spring inside rotating disks under the top tension disks. They allow for spring tension (loosen a set screw and use screwdriver blade to tighten or loosen the spring), spring travel (via a curved stop bracket on the bottom of the spring) and a curved slot adjustment to fine tune the amount of extra thread that is allowed on the downstroke. By playing with the check spring adjustments you can get a larger, longer lasting loop for the hook to pick off.

[Gymnast]

Thanks for the advise, @Wizcrafts 

I have tried to vary this check spring stroke, but it did not change anything. But what did a big change was more obvious - needle size. I have normally used size 14/90 or 16/100 with this thread. But I now tried size 18/110 and 19/120. And 18/110 worked best. Perhaps I should not have asked with a solution like that

I think the theory here is, that you need to have low local thread tension at the needle eye when the needle is at its lowest position. The thread tension here will pull down the stretch fabric from previous stitch. When the needle rise the stretched fabric will pull up the thread again, so no loop or a smaller loop is created. With lower local thread tension at needle eye, the deflection of the fabric will be less, and then a bigger loop can be made.

A bigger size needle got a larger grove for the thread, so the friction against on the thread from the fabric will be less when the needles advance to lowest position. When I look at the thread tension above the fabric it is zero regardless of the check spring adjustment when the needle is at lowest position. But I acknowledge, that for some other machine this might not be the case, and then this adjustment of check spring stroke would be important.

I have tried sewing the same with a Bernina 910. This machine needed a size 19/120 needle to be able to sew at the same conditions. With the 18/110 needle the machine occationally made a birds nest of upper thread below the fabric. I suppose the hook stabbed the thread. This machine got a special check spring, that you cannot adjust. It also struggles more with feed tracktion on this fabric. However the stitch got more balanced in both sides of zig zag. The singer 237 produced stitches with the lock at the top fabric surface to the left and near lower fabric surface to the right.

[Gymnast]

I did succeed making some patches of the cover. This is photos of the inside and outside of the cover, and the patch size is about 2½ x 3 inches. The stitch width is about 1/8 inch.

Of couse I like your comment on this repair.

So it is possible to sew such a difficult stretch fabric with a vintage zig zag machine. I got some comments elsewhere, that I should use thinner thread and a stretch needle for it, and it might be better. This top cover is about 7 x 10 feet in all.

[Handstitched]

G'Day,

Just wondering if a different fabric on the back ,like a calico or thin canvas( with same or similar colour)  that has  a much   tighter weave would  help. My Mother makes an assortment of handicrafts  and teddy bears etc. using a domestic machine. She's sewn quite an assortment  fabrics over the years and calico has been quite a big help with ' furry teddy  bear fabrics'  that are a bit stretchy ( she used to be a seamstress by trade in her younger days   )  I  now have her old  'domestic machine' , a Pfaff 60. 

HS 

 

[Bert51]

I have found that sewing any stretch knit fabric, Heavy or light I need to use SUK needles and back off your top tension a little.

SUK Needles are Ball Point needles and I have found them to work well on all stretch or elastic materials.

Bert.

[Gymnast]

I think that canvas do not have sufficient stretch as the rest of this fabric. If I use a patch of canvas here, the forces locally to the seams can be significantly higher. The patch and the seams needs to be able to stretch. 

I found some limitations on what you can get of domestic sewing machine needles. When I look on websides for Organ and Schmetz, the max size jersey needle is 100/16, and the max size stretch needle is 90/14. The stretch needles should have a different scarf, so some sewing machines can catch the thread better. Some vintage machines may not be able to take advantage of a stretch needle.

However there seems to be some jersey needles around of size 110/18, but this is the only supplier I found (Sharp Sewing Supplies in US):

https://www.amazon.com/Titanium-Sewing-Machine-Needles-Multiple/dp/B07NQNWVP2/ref=sr_1_22?dchild=1&keywords=Organ%2Bneedles%2Bball%2BHAX1%2B110&qid=1601984198&sr=8-22&th=1 

Another option may be to use thinner thread.

I agree, that the top tension is less than normal. SUK needles - is it stretch needles?

Edited October 8, 2020 by Gymnast

[Northmount]

Be careful not to stretch the fabric while sewing.  If you stretch it, if will pull back on your thread reducing the loop size.

Tom