MaryelR

Thank you both. New thread arrived today, I seem to be up and running! Really appreciate all your help.

I wouldn't have thought to use a round point. The covers are heavy paper. A minor problem I'm having is that the holes on the back of the sheet (bobbin side) are very large - the needle appears to be tearing through the pages. Would round point needle help with that?

Not to worry! The machine is not Seiko brand, but one of many equivalents - its documentation has it listed as #25 - #27 and it shipped from the manufacturer with a #27 needle. I just loaded some nylon upholstery thread with a #21 needle, and it works perfectly. I can't believe my problem was the thread! Feeling very silly. Thank you so much.

Thank you so much for all your responses! I just ordered some bonded nylon thread in size 92 and 138. Maybe that will also reduce the overall friction enough so I can pull the thread through the machine more easily? The Fil au Chinois linen isn't actually waxed, but glazed with potato starch and has a tight Z (left) twist. I was hoping it would be a good machine alternative to typical linen bookbinding thread. Is it possible to use linen thread successfully with a machine - or is linen simply too weak? This explains a lot. I've been using too small a needle for the knot to pull through, and as a result I probably have the tension too high to compensate. I've found that with some adjustments, the machine can take anywhere from #21 to #27 needles. I will try again with a larger needle and see what happens. I can't thank you enough. I've been struggling with this for many weeks - it's such a relief to have some input!

I have a new (to me) Seiko SK-2B-1-20, long arm walking foot machine and have trouble-shot everything I can - set the hook timing, needle bar height, adjusted feed dog & presser foot. It's working okay. This is my first time using an industrial machine - I have used many small machines. I'm using this machine for sewing books - sewing through about 3/8" thick paper. I can do this work on my old Singer, but the stitch length isn't variable, and I needed longer stitches. I also wanted working space for wider books. My question is regarding thread tension and thread weight. I'm trying to use Chinois linen thread, #532 and it keeps breaking. It's very hard to pull the thread through the machine, there's just so much tension. If I set the tension any looser, I get loops on the back of my work. I have to use two hands to pull the thread through before starting or at the end of my piece. The mechanisms are all about the same as those on my old Singer, so I don't know why it would require so much more tension to work. I have adjusted the bobbin tension - it's as tight as can be, though the bobbin thread is much looser than the top thread. Is it possible to use this machine with lighter weight thread or does it have to be very thick thread? I'm worried I may have bought the wrong machine. Any help or advice would be much appreciated. Thank you.