Pauls Leather Report post Posted June 27, 2017 (edited) My issue I need help with: I keep seeing the bottom thread pull to the top. basically flush with the top surface. Equipment specs: CB3200 Thread - 138 & 207 (I explain why the two) Needle 19/120 or 23/160 Leather thickness: I'm needing to use on oil tanned leather that at a minimum is about 7oz. thick. I've tried tightening the bobbin tension to almost the max and have loosened the top to see if the bottom will help pull it down further. The two needle sizes and thread sizes are what I'm having issues with since I'm trying to sew thinner leather. The 277 thread and 25/200 needle which corresponds to the thicker leather my machine can do is no problem. Is what I'm trying to sew just too thin for this machine? I notice on 10-18oz thick it does fine and pulls center within the leather. Thanks in advance Edited June 27, 2017 by Pauls Leather Quote Share this post Link to post Share on other sites
JLSleather Report post Posted June 27, 2017 How are you routing teh top thread? Quote Share this post Link to post Share on other sites
Wizcrafts Report post Posted June 27, 2017 Perhaps the top thread has too much tension when at rest. This can be caused by wrapping it around a top post, rather than simply feeding it straight through a hole. Or, the thread check spring might have too much spring tension for your thread. This spring is normally set with a lot of tension because it is usually dealing with larger sizes of thread than 138. It has to keep the top thread under tension as the take-up lever moves up and down. It also has to move all the way down to its bottom stopper bracket as the needle meets the top of the leather. The check spring tension can be decreased by loosening a nut on the reverse side of the head to where the bottom roller mounts. Then turn the split threaded shaft with a screwdriver blade to reduce the spring tension to the point where it just is able to go all the way down to the stopper on its own. Tighten down the nut on the back and see if this helps stop the knots from pulling to the top. If you need to sew with #277 or larger thread, that spring needs to be tightened up again. Quote Share this post Link to post Share on other sites
Pauls Leather Report post Posted June 27, 2017 Thanks. I'm going to work on trying that and will report back. Most of my work will encompass what I'm trying to set this machine up for but I know another machine dedicated to this is in short order. I don't want to have to figure it out every time I need to change. Quote Share this post Link to post Share on other sites
Pauls Leather Report post Posted June 27, 2017 3 hours ago, JLSleather said: How are you routing teh top thread? I'll get back with you on that so that I use the proper jargon but I believe I am doing it the proper way per instructions. Quote Share this post Link to post Share on other sites
JLSleather Report post Posted June 27, 2017 Note that sometimes just downsizing teh needle one size can help here ... Quote Share this post Link to post Share on other sites
Pauls Leather Report post Posted June 28, 2017 22 hours ago, JLSleather said: Note that sometimes just downsizing teh needle one size can help here ... Thanks. I did notice that going down to a 7x3 19 needle it did help it. I then further loosened the top thread tension and notice it started to get better sewing two pieces that add up to the 7-8 ounce. I'm getting much better consistency now but still need to loosen and am surprised that the nut is almost at the end of the thread. I'm guessing a 7x3 18 might be to small for a 138 thread. I feel as if the 138 is the max for the 19 needle. Quote Share this post Link to post Share on other sites
JLSleather Report post Posted June 28, 2017 That's why I asked about top thread path. Your needle/thread combos seem about right. On a project I just did, I was able to "smooze" through by 'shortening' the top thread route.. as in wrap around teh tensioner ONCE instead of the twice that would be "normal". First time I've had to do that.. and it was due to the bottom thread pulling up way too much. Problem solved. Quote Share this post Link to post Share on other sites
Wizcrafts Report post Posted June 28, 2017 I'd like to follow up on my previous post about what to check for excess top tension. In it I mentioned that the default setting for the check spring was very strong and based on tensioning #277 thread and up. I will expand upon that now... Sometimes I use my CB4500 to hem jeans! When I do I use jeans #80 poly-cotton blend thread with a #18 or #19 - 7x3 round point needle. This thread is made with tailoring machines in mind, not huge harness stitchers. To sew with it I make some major adjustments to the top and bottom tensioners, as follows. After winding a bobbin I adjust the bobbin spring for a modicum of tension, but nowhere near as much as I use with bonded nylon thread. Next, I make sure that the top thread only passes straight through one hole in the top post. I back off the upper tension beehive spring I loosen the securing nut behind the bottom shaft set and turn the shaft to loosen the check spring to the minimum tension needed to allow it to bottom out on the downstroke. I run a test stitch and make last minute adjustments to the top tension. If the knots appear on top despite all lowered tensions, I tighten the bobbin spring to bring the knots down. The reduced tensions also lay looser stitches. So I shorten the stitch length to 8 to the inch. Sewing with #138 bonded thread on a 441 machine that is set up for heavy thread requires similar tweaking to balance the knots. The usual suspect is the check spring tension and travel being too much for the light weight thread. Quote Share this post Link to post Share on other sites
JLSleather Report post Posted June 28, 2017 18 minutes ago, Wizcrafts said: The usual suspect is the check spring tension and travel being too much for the light weight thread Thanks Wiz -- informative as usual. Quote Share this post Link to post Share on other sites
Pauls Leather Report post Posted June 29, 2017 Thanks for the additional information. on my top post I only went thru one hole. and on the top tensioner I tried that loop 'once' instead of 'twice' and that seemed to help a bit more but I'm beginning to think that the stroke like you said might be too much for thinner leathers. Quote Share this post Link to post Share on other sites
Pauls Leather Report post Posted July 10, 2017 (edited) Thanks everyone for the suggestions. I loosened up as advised and experimented with different needles. While I got some satisfactory results they were not ideal to continuously use. I reverted back my original setup and it's doing great. I decided to go ahead and add another sewing machine that has a great range from #33-#138 thread. I always knew I would need a second machine but I was anticipating to get it so soon. I guess demands change. BTW, I'm getting a Cowboy CB341. have to wait about 4-6 weeks though. Edited July 10, 2017 by Pauls Leather Quote Share this post Link to post Share on other sites
