issues with stitch and shuttle hook thread

[1985]

Hi all,I have a major issue with my singer class 7 double needle oscillating shuttle hooks,and thread ,

At the moment I am only using the left side needle trying to sort out one side first,on this twin needle singer class 7 machine. It does not matter what needle and thread combination I use the same issues occurs, seams to stitch for longer in thicker leather and worse in thinner leather, issues in thinner leather happens after 4-5 stitches issues with thicker leather can occur as soon as 10-30 stitches`s,

I start stitching `then I will notice as its stitching the thread looks like it wants to twist more in the leather, and when the needle is travelling up and left the leather the thread looks like its twisting and some times fraying some time both together,  but the twisting seams to happen a few stitches first before fraying. then it may fray it may not. if I carry on two or three more stitches the twist will get worse and go as far as the thread pick up leaver as shown in the picture,  

Some times the hand wheel will not move` stuck firm, where the thread had got trapped underneath when all stitches top look good and no sign of twisting above, but when looking underneath where the thread had tried to leave the back end of the hook ,its gotten trapped,

other times there has been a double loop  occurred or where the hook for some reason won`t go around to finish the cycle , because when  I cannot pull the leather away with out cutting the thread,then I noticed the second loop not completed,

The whole machine has been cleaned up all the shuttle hooks and the race and needle plate and all the run ways where thread passes all good and all the tension discs  have been cleaned polished and checked , the needle thread guide by the needle no longer has thread cuts into it ,needle is set at correct height and distance from hook, and checked for sharp area on the shuttle hooks that may cut the thread has been checked.its all been well oiled , needles have been replaced with new, thread been changed to other types as well , but the issues still posits every time I sew,  

  The last time it got snagged I cut the thread removed the leather removed items up above to inspect what had gone wrong on this particular moment. This time the thread had gotten (inside the hook) made its way to the spring as shown in the pics and the spring had come out of its hole laying as shown, 

I do not know how or whats happening causing the thread to get where it got to, Im thinking as the stitches look good surely it is not a tension issue , I have also threaded the machine several different paths just to see if it stopped the issue but it never  , I Don`t know if the bobbin case may be moving slightly while in the hook assembly causing the thread to be snagging on the case as it slides over it, or to muck rocking back and forth with the hook in the race whether its moving faster or slower causing it to trap the thread, or is the bobbin thread tension to tight or to loose, or is there wear that the shuttle hook has to much movement from side to side as it goes around, but it feels good snug,or some how is the timing out,

I am at the end of my options to why this keeps happening,and why they would make the shuttle with the gap partially so far and not have it as a complete hook going all the way around the bobbin case,like iv seen on the majority ,

I also made many types of tension springs for the front plate but this never changed the out come either ,so in the end I just tied it up to stop it moving so much, out of frustration,but on the pick before un threading you can see the twisting going up towards the thread take up 

 

 

 

[1985]

Okay I resolved the issues , like I said very new to sewing machines and realized the 2 frustrating issues were as follows.

The thread getting trapped where it showed on the bobbin case` was top tension issue, being to lose or tight cant` remember now as been a while, moved on to the 7-33 single needle ,The top tread was not sliding nicely across bobbin case but not really indicated on the stitch at first,  something else had contributed to this issue and the other issue . I realized all my focus was on the top thread + needle +material+ and machine parts being clean and damaged free, but the bobbin thread combination with top thread was the major cause,

The top thread was bonded poly nylon or something of that sort and must of had more give but after several stitches due to the bobbin thread  , the bobbin thread being thinner but was old a (non) poly nylon thread due to it being left on the bobbin when bought machine not checking what was on there first` 

So the top tension thread had plenty of give where the old thread never and different wights so ` So the combination of the 2 wrong matching threads caused top thread to fray and snap strands hence the twisting, and constant issue with thread going around bobbin case, getting trapped and not coming up out the back in time,

Once I corrected bobbin thread with same as top thread all issues were gone and machine stitched great.I had many people helping that kept telling me to check Top thread for its quality and how it comes of the spool/ correct needle and look for damage , correct tension top and bottom/ material I am using may have defects in the leather/ parts worn or damaged to machine/ check timing and feed dogs/from you tube and sites but no ever mention of matching the type of thread used as in there material make up had to match.only the thickness.

But now I know I can get away with slight difference in the thickness from top and bottom but no so much the type if complete different.make up. By not replacing the bobbin thread this lead me down a rabbit hole over 2-3 weeks even stripping machine so far where I was on the verge to give up,

I think lessons were learnt in my case , its natural `also taken for granted one would of replaced bobbin type thread to the same type used on top and commonsense for the average user of a sewing machinist to check what thread or even just replace bobbin thread straight away, but not to a newbie,

Specially when stitching tension looked good on the material and the thread looked similar size to the naked eye and its make up , until checked later then it hit home.Its very easy to look over this specially when 99% your told to look more on the above areas,

The one other lesson learnt by my self is don`t assume that the last owner has left the machine with the correct adjustment settings and the correct thread in bobbin that they gave me with the spools for on top, I never new the working of a basic function sewing machine much , but after all this I am pretty well adverse now how it works and how to set timing etc, on this basic machine, I kept telling my partner if I give up on this I would not know how to check issues with my other several vintage machines,that may be more complicated in there functions.we all start from the beginning and teaches us allot.

So thank you to all helped it had been a big learning curve with machine and man.

[Frodo]

Have you heard of using a fish scale to set your bobbin tension?

or. Another method is the drop test 

hold the thread and drop the bobbin it should not fall under its own weight but should move if you pop your wrist like you are fishing.  

[Northmount]

@1985 Moved your post to leather sewing machines.