1. When selecting, check whether the machine head is bright, whether there is paint peeling and bruising, whether the electroplating layer of the needle plate, push plate, face plate, upper wheel, etc. is intact; whether the platen is straight, whether there are cracks or partial discoloration in the paint; Whether the frame is broken, painted off, or twisted; whether the clearance between the upper shaft, the lower shaft, and the needle bar meets the standard requirements.
2. Remove the belt, lift up the presser foot, and gently rotate the upper wheel to see if it runs freely and whether the needle is raised and lowered in the center of the needle plate hole.
3. Whether the sound of the machine is soft when rotating.
4. When trying to step on and sew, first try to sew with two layers of thin cloth to check whether the stitches are smooth and even. Then try sewing with the original fabric to see if the stitch length can reach 3.6mm, the seamless material does not go or the noise is abnormal, etc.
5. A more specific inspection should have a sewing machine maintenance worker on site.
For more information about industrial sewing machines, please log in to my website https://www.suote-sewing.com/ for inquiries, I hope you can help you!