Wrong Needle Depth – this causes thread splitting where one ply continues to sew while the other ply peels back. The thread eventually breaks leaving previous stitches thin & wimpy looking. Hitting a hoop frame is a common way to throw off the needle depth. The needle eye should be at least half visible inside the hook basket when it at the lowest point in the stitch cycle.

Wrong Timing – this shows up in many ways, from broken needles & no stitching to poor quality stitching & thread breaks.

Trimmers not working properly – this can cause the tread not to be cut all the way through leaving an untidy appearance, or the thread can be trimmed too close causing the stitching to unravel.

Needle too close to the hole in the needle plate – this causes the thread to rub against the edge of the hole in the needle plate & eventually break.

Nick or Burr – a cut or a barb on a needle usually caused by a needlepoint hitting on one of the following parts: the pressure foot, edge of the needle plate, the rotary hook or the retainer. Nicks & burrs cause thread breaks.

Hook basket retainer too close to the needle – when the hook timing is set the distance away from the back of the needle scarf & also the retainer spacing is set. If the hook is too close to the needle or the retainer is bent, the retainer won’t allow the thread to pass in-between.

Incorrect Tensions – this is one of the main reasons for thread breakage. If a bobbin is too tight it will cause the upper thread to break. If the upper thread it too loose it will leave loops through the fabric at a rate of about 10 per second. If the upper thread is too tight it causes breakage.

Holding the loose end of the thread during start up or winding it around the side holding disk can cause the needle to bend slightly & cause it to break if it hits the plate, holding the thread can also cause the thread to break.

Birdsnest – this is a blob of thread under the plate, this is usually caused by incorrect timing of the heads, or the hook not being close enough to the needle as it passes by, it can also be caused by the bobbin not being threaded correctly, the plate not secure, or a spring that is too loose, or too tight. WARNING if a garment gets caught & pulls down into the hole in the needle plate do not try to pull it out because you will likely tear the garment. Instead go to the bobbin area where you will probably find a large birdnest, carefully trim away the birdnest, take your time & trim only the embroidery thread & not the garment.

Thread breaks – the main reasons for thread breaks are caused the problems with needles, machine mechanics, & thread.

Needle Problems: burr on needles, bent needle, wrong size needle for the thread weight,point not aligned properly, needle clearance, lint/adhesive build up on needle, improperly installed needle, improper finish on needle.

Machine Mechanics: rotary hook needs oil & thread is overheating, burr on the hook, bobbin plate is scratched, upper tension or bobbin tension is wrong, hook is dirty, thread is getting caught in trimmers, machine speed is too fast or too slow, hook timing is set improperly, the clearance between the needle & hook is set improperly.

Thread: wrong weight of thread is being used for the needle size, thread is bruised, thread is old or dirty, adhesive residue on thread, a knot in the thread.