Two flat layers can sew easily while their folded seam intersection stalls. At the crossing, the foot climbs a step, the stack thickens and contact with the feed system changes. Stop at the first sign of force and identify which limit you have reached.
Which of these describes the obstruction?
What a leveling feature actually does
The Brother NX-650/650Q manual illustrates a holding pin on its zigzag foot for maintaining a level position at a thick start. That is an exact accessory example; a similar-looking foot may not have the mechanism.
Brother’s heavyweight-fabric guidance also warns against forcing fabric. A machine continuing to make needle holes while the work is stuck is not successfully crossing the seam.
The sample must contain the step
Recreate the folds, allowances, interfacing and direction of travel from the difficult join. A flat pile of denim misses the very obstacle you are evaluating. With the recommended needle and thread, the sample should advance and form sound stitches without pushing or pulling.
If the assembly exceeds the machine’s comfortable capability, examine whether the pattern permits a less bulky finish or a different order of construction. Do not trim structural allowances indiscriminately. For repeated heavy joins, take the sample to a dealer; fabric names and layer counts alone cannot decide the purchase.
