I was using an old metal desk that was extremely heavy to sew on. Never had a problem. When we remodeling my sewing room, I switched the old desk for a newer one with a huge top. The newer desk had been used by a drafting firm and I thought it would be wonderful to have so much space. Now my table top seems to be "jumping". Disappointing but I'm not saying a word to my hubby or the crew it took to bring it into the house.