I recently received this comment on one of the earlier articles in my blog, about tension adjustments for sewing jeans:
I have a commercial machine and I’m using a 18 needle but the thread breaks. It sews about three stitches and breaks, but when I put it on a thin material it looks beautiful. Can you tell me what I’m doing wrong.
Here is a checklist to help solve the problem. I tried to arrange it roughly in order from simplest fixes to the more involved ones. And since the reader was asking for help with an industrial machine I’ll try to take that into account as well.
Starting with needle and thread:
- Try a different needle, same size. The needle you’re using might be defective in some way, such as burrs at the tip or being bent.
- Try a different bobbin. Again, the bobbin you are using may be defective, or the bobbin may be wound incorrectly.
- Are you using the same thread on top and in the bobbin? You should.
- Are you using cone thread, rather than spool thread? Industrials are meant to use cone thread. Cone thread is wound in cross-diagonals, and when used on industrial-style thread feeds the thread unwinds without twisting.
If you put a regular spool of thread on an industrial thread spindle, it will gradually twist while sewing and can cause poor stitches and possibly thread breakage. (If you have a home machine, you can use cone thread with an appropriate cone thread holder).
Here is some additional information on cones versus spools, and when it is appropriate to use each: Thread Delivery System
- Is the thread the right size for the needle? If you are using a large-size needle and thread that is too lightweight, this can cause stitch problems. You should user a heavier weight thread with a size 18 needle.
Along similar lines, if you use a topstitching needle, you should use topstitching thread along with it. A topstitching needle has a longer eye and is intended to accommodate thicker thread.
Here is an article that discusses the relationship between needle size and thread size in detail: Technical Advice: Needles and Thread
- Is the thread old? Old thread can degrade and become brittle due to exposure to sunlight or air, and can break when used in the machine. Give a tug on the thread to see how much it can take before it breaks. Sometimes you can salvage a spool or cone of thread by unwinding the outer, brittle layers of thread and tossing them.
Next, check your machine setup and usage:
- Always make sure the thread take-up lever is always at the top of its travel when you begin or end stitching. Otherwise, the thread can break, or the needle can come unthreaded. This sounds super simple, but it was a problem I had working with industrials (and mechanical sewing machines in general) before I was properly taught how to use them.
- If you have an industrial machine, check that the needle is installed correctly. Industrial needles do not have a flat section at top to ensure proper orientation, as home machine needles do. Make sure the long groove shaft of the needle faces to the left (towards the left hand side of the machine) when you install the needle.
- Make sure the bobbin is installed in the case so that it turns clockwise when you are looking at the open side of the bobbin case and pull on the thread.
- Make sure the bobbin case is installed in the machine properly. On the Juki industrials I am familiar with, install the bobbin case with the open notch pointing upwards.
- Industrial machines (and other high-speed straight-stitch machines like the Brother PQ-1500S, Janome 1600P, and Juki TL-2010Q) have lots of little twisty guides and discs the thread must go through, in order to stabilize the thread for high-speed operation. Miss just one of these guides and you can have stitching problems – ask me how I know! Rethread the machine from scratch, and recheck the threading diagram closely.
- Remove the needle plate from your machine, and with a small, lint-free brush clean up any lint or fuzz that has collected in the bobbin area. Accumulated lint in this area can cause the machine to malfunction.
- Check your machine for nicks, burrs, or other damage to the needle plate, thread guides, and other machine parts.
Finally, some things that involve adjustments to the machine.
- Try checking the top thread tension. If the top thread tension is too high, the bobbin thread can break.
- If top tension adjustments don’t help, try checking the bobbin tension. Here is a test for bobbin thread tension: You should be able to pick up the bobbin case by the thread, and the bobbin case should just hang on without sliding to the floor. If you give a little upwards yank on the thread, some thread should come out of the bobbin case.
Adjusting the bobbin thread tension on a commercial machine is pretty much the same as on a home machine. Here are some articles on thread tension that explains how to adjust both top and bobbin thread tension: