Brother LS2-F52A versus Singer 211-G165 The hunt continues! in Leather Sewing Machines Posted July 13 · Report reply 6 minutes ago, Wizcrafts said: Several years ago, I tried sewing 8 ounces of chrome tan (4-5 oz) lined with suede (3oz), with #138 thread and a #23 needle, at different speeds and found that the needle started smoking at about 9 stitches per second. Above that the smoking got worse and the thread eventually melted or shredded. As I read your comment, I was thinking, wow, 9 stitches per second is screaming fast. Then I did a little math and realized 2200 SPM is over 36 stitches per second! I think some of my back tack problems might be caused by the needle size. I'm using a #22, which is a little borderline for 138 thread. Last time I went to buy needles, I couldn't find anything larger than a #22 in a 135 x 16 size.