Bests & Worsts Reviews from Amazon

this is my 2nd singer heavy duty. Both died with the same problem: The bottom thread just tangles under the fabric, and does not interlock with the top thread. no actual stitches are formed, and I end up with a huge birds nest of a mess on the underside of the fabric. The first machine lasted for a while, and I definitely beat that thing up. Sewed denim, leather, and many layers or cordura D1000. So after it died, I wrote it of as my abusing it. So I bought a new one. The same problem arose after about 50"of stitching, and no leather this time. I've read about this problem in other reviews, and since the same thing happened to me on 2 machines, one practically out of the box, I think there is a design flaw in this thing. At least, don't sew heavy fabric with it! I missed my return window, so I just wrote it off as a loss. Save yourself the trouble!