When your embroidery machine stops trimming thread, production can grind to a halt. In most cases, the issue comes down to two main causes – a damaged black knife or a misalignment between the black and silver knives. Knowing how to identify and fix these problems can save you time and frustration.
Step 1: Inspect the Knife Assembly
Remove the needle plate to access the trimmer mechanism. You’ll see two parts: a silver articulating knife and a black stationary knife, often stamped with “SWF”. The black knife does the cutting, while the silver knife moves against it.
Run your thumb carefully along the edge of the black knife to check for nicks or burrs. Even the smallest imperfection can stop the thread from cutting cleanly. If you feel roughness, the knife will need repair or replacement.
Step 2: Test the Trim Function
Next, test how the knives work together. Swing the silver knife out, loop a thread around its edge, and slowly push it back under the black knife. If the thread trims cleanly, alignment is fine. If it doesn’t, the black knife may be set too high or low, or at the wrong angle.
Think of it like scissors with a loose pivot – if the blades don’t meet precisely, nothing cuts.
Step 3: Adjust or Replace the Knives
If the black knife is nicked, it must be replaced or resurfaced. This requires precision work, as the cutting edge and alignment are critical. Adjusting knife height and angle is also delicate – even a small mistake can make trimming worse.
It’s often best to let a trained embroidery technician handle this repair. They can realign the knife block, test the trim, and ensure everything works to factory standards.
When to Call a Professional
If trimming still fails after inspection, don’t waste hours troubleshooting. Send the knife block to a repair specialist. They’ll quickly identify worn or misaligned parts and get your trimmer cutting perfectly again.
A sharp, well-aligned knife set keeps your embroidery quality consistent and your machine running efficiently.