WhiteBuff Report post Posted February 17, 2017 (edited) My cobra is not letting me sew a knife scabbard , it is very thick between 1/2" and 5/8" , not sure what's going on, 200 needle 277 thread, it is not picking up the bobbin and pulling the top thread in half, dropping over half of the stitches, please help. thanks Clint Edited February 17, 2017 by WhiteBuff Quote Share this post Link to post Share on other sites
MADMAX22 Report post Posted February 17, 2017 Does it sew say quarter inch of leather correctly? Ya probably need to tighten the presser foot pressure (silver threaded guy on top with the lock nut on it), cranking that down some. It may not be tight enough allowing your project to lift as the needle comes up thereby not forming a loop big enough for the hook to grab. This video shows just about most of the things to adjust on these machines. https://www.youtube.com/watch?v=IkxZlczFqRY&t=300s May need to adjust the banana bar also unless it is otherwise feeding correctly. Im sure Wiz or Bob or other sewing machine mechs will chime in. Quote Share this post Link to post Share on other sites
brmax Report post Posted February 17, 2017 Didn't possibly get a bur on the tip of the needle. I find the shuttle cap on mine sits in the draw a lot, i guess the ability to look see keeps me interested. So might take a look while some extra material is ran through. Floyd Quote Share this post Link to post Share on other sites
RockyAussie Report post Posted February 17, 2017 Picture doesn't show the stitching and so can't judge the needle type but If it stitches ok on a lighter weight leather and is not out of timing I'd try a 230/26 Lr or tri point. I used a 230 needle with my CB 441 in a heavy belt recently and it looked pretty good. Quote Share this post Link to post Share on other sites
WhiteBuff Report post Posted February 17, 2017 Ok, I tried a thinner work piece aproxx. 1/4" and the bobbin thread is being pulled more than half way up almost to the top, it still sounds like it's dragging and fraying the string. Quote Share this post Link to post Share on other sites
Wizcrafts Report post Posted February 17, 2017 Splitting the top thread comes from the hook and loop not meeting at the proper moment, or a loop that is too shallow. The check spring is in charge of controlling the formation and size of the loop. Make sure that it doesn't have so much travel downward that it fails to let go over the top thread as the needle goes down through the leather. Most of the time, the best adjustment of the check spring is to reach its bottom stop just after the needle penetrates the top layer. The opposite can be a problem too. If the check spring has way too little movement the top thread will be too loose and can fray on the way down. You can prove this by experimenting on scrap leather with the top thread not going through that spring. Did you by any chance forget to thread through the check spring? If the threading path and check spring travel are correct but the thread is getting frayed, causes include burrs on the needle, throat plate, or tip of the hook, or timing too far advanced or retarded, or badly bonded thread, or thread passing through a guide that has a sharp edge. Skipped stitches can be attributed to bad timing of the hook or insufficient presser foot pressure. If the ascending needle lifts the leather even one iota, a skipped stitch may occur. Crank down the top pressure spring until the leather doesn't lift with the rising needle and thread. Keep in mind that an unthreaded needle has less resistance to overcome than one that is pulling up a lockstitch combination, especially with large thread sizes. Quote Share this post Link to post Share on other sites
brmax Report post Posted February 17, 2017 Maybe my eyes but in the pic the thread looks like it on both sides of break is or has been running tite. I would check top thread path and pull off 8' of thread from the spool and keep it clear for another test. If possible have someone keep an eye on the thread in its path when moving. I have thought before my needle was fine with me scraping my finger on it while still installed, yet when removed an easier and better assessment was found, more than once! good day Floyd Quote Share this post Link to post Share on other sites
SolarLeatherMachines Report post Posted February 21, 2017 On 2/17/2017 at 10:34 AM, WhiteBuff said: I tried a thinner work piece aproxx. 1/4" and the bobbin thread is being pulled more than half way up almost to the top, it still sounds like it's dragging and fraying the string. Hey guy, I'm in Arlington, just outside of Dallas. If you want to bring me just the head, I can sort it out for you. We have a test bed that we'll mount it on. Quote Share this post Link to post Share on other sites
