batik problem
 

I am using a size 70 needle and polyester thread, why is my machine skipping stitches when I am piecing with batik fabric?

I'm not so good on the needle sizes, I prefer to use a smaller needle, what I would call a 10 for piecing. I'll go up to 12s.

For batiks, and especially when quilting, I like to use the Microtex Sharps.
https://www.schmetzneedles.com/schmetz-microtex-needle/

What type of needle are you using?

Try a Microtex 80/12. These are the needles that I generally use for projects.

Any time there are issues change out the needle for a new one.

I use poly embroidery thread for piecing without issues on batiks. Stitch length defaults to 2.5 and I use it.

Are you using the same thread in the bobbin?

Following this thread to see how others have resolved this problem. I have experienced it a couple of times and changed to every different needle size and type I owned and changed thread. Fought it all the way and finally called it done after the seams had been sewed at least 3 or 4 times and was as good as they were going to get. In retrospect, I could have finished quicker if I had hand stitched the parts where the needle skipped. Next time.....

Edited to add: Every time our local Hancock's would put needles on sale at 50% off, I would buy every wacky off the wall type and all brands. My inventory is still pretty extensive. I really miss Hancock's. It used to be my favorite fabric store.

are you using a universal needle? they might not be pointy enough, I'd try a microtex

It's my understanding that the needle needs to fit with the thread size. I would use a 70 needle with a 60 wt. cotton. For a 50 wt. cotton I can get away with a 75. I usually piece batiks with a microtex needle.

organ brand needles
for batiks, either a 75/11 or 80/12
50wt or 60wt cotton thread

My machine never used to mind batiks or anything else, but it had a huge overhaul....and wham! Had to find another repair person to reset everything....but since all that...it is very touchy about needles.....I thought I was going to have to take it back to the repair shop....but after all other needles kept skipping...I googled and found the Microtex needle suggestion...Yay! I have been enjoying my machine again.... hope you find the same for you.

I always use Microtex needles in all my machines. I seem to have a lot fewer problems that way. I agree that you do have to fit your needle size to your thread for best results. I normally piece with Aurafil 50 wt and a Microtex 80/12. It seems to work well on all the fabric I use.

For me, polyester thread and batiks do not get along together, I've always matched my thread with what my fabric is. Since batiks are cotton, I only use cotton thread. I can't remember what size needle I'm using currently, but Aurifil has some fantastic cotton thread, 30 weight that I'm using for my grandmother's flower garden.

You might also consider re-threading a new bobbin and pay attention to how it's being threaded. I actually just went through this not too long ago, there's a video on YouTube that shows how a bobbin should be threaded correctly and it fixed my skipped stitches. I was surprised to discover that something as simple as threading a bobbin can cause issues if you don't do it the right way. I did change out my needle, as well.