sewing machine problem

[chal]

I'm trying to sew a new sail cover, should be a fairly basic job. I have a decent sewing machine, not a proper sailmaking one, it's a very solidly built oldish Jones domestic model. It doesn't have any problem pushing the needle through several layers of canvas, but the thread keeps breaking: often I am lucky if I can get more than an inch done before the upper thread snaps. The thread off the bobbin doesn't snap. I've got the tension on both upper and lower threads set to pretty much minimum. Following advice on other threads I have seen I have bought large size needles so these should be both the right size and sharp. I have noticed that although the stitching looks ok on the upper side, it tends to be a complete mess on the lower side: too much thread seems to get pushed through so there are big loops on the underside.

I'm guessing this might be some sort of tension issue but don't know what. I have the tension on both bobbin and upper thread set to minimum (the bobbin only has a grub screw to tighten so not very precise but any looser and the screw falls out: it seems to be ok and thread is coming off the bobbin). If the thread is snapping, it seems to me to imply that the tension is tight enough.

I've tried with 3 different threads: V92, V69 and a bonded nylon. I temporarily seemed to get better results with the latter in terms of it not breaking so readily, though still had the bunching on the underside. I've noticed that when the thread breaks it unwinds a bit and catches on the needle (so there is a sort of ball of it that won't go through the eye), but whether this is a result or cause of the breakage, I can't tell. Here are pictures of the stitching above and below (ignore the not-very-straight line!). This is just a single thickness for testing but it's the same on 2 or even 3 thicknesses.




Any ideas what is going wrong?

 

[ip485]

Can you adjust the tension on the bobbin?

 

[Gin]

I've experienced similar tangles and I am no expert but I think it is probably a feeder problem- too many layers causing the material to drag and resulting in the tangles which in turn cause the upper thread to snap; it could also be that the bobbin tension is too light and allows the top thread to pull too much through.

Try a sample run with the feed dog disengaged and feeding through manually- this requires a bit of practice and at first may cause even greater annoyance!

 

[cpedw]

I think you need a lot more lower thread tension. A crude test on my 30+ year old frister Grossman is to try to pick up the bobbin by the thread. Tension should be just enough to lift the bobbin. You will then probably need to adjust the upper tension to get similar appearance top and bottom. If the thread still breaks,try a new needle. Sometimes there's a sharp edge on the needle eye that cuts through.

Derek

 

[VicS]

I'm trying to sew a new sail cover,

Any ideas what is going wrong?

Could you have slackened the tensions off too much ...........you say when the thread breaks it appears to unwind a bit. .... It looks far too slack to me in the picture.

I take it that the bobbin case is like this and the tension is adjusted with the screw shown.

The tension should be such that it will just support the weight if held up by the thread but slip if gently jerked.

Are you threading it correctly ? RTM ??

Has the machine been properly serviced recently? ......... SWMBO had a Frister Rossmann ....... That was troublesome with thread tensions but the Sewing Machine shop seemed to be able to set it up correctly when it was serviced. In fact the whole thing ran much better.

 

[AngusMcDoon]

Certainly more tension on the bobbin. From your second picture the tension from the top is pulling the bottom thread into loops from one stitch to the next until it all gets in a tangle and the thread breaks. Each thread should be disappearing into the fabric on each side. If you can see the thread from one side at all on the other, even if just tiny loops, the tensions are not balanced.

 

[doug748]

If the thread is bunching under the fabric you have too much tension on the bobbin - or conversely too little on the needle (Google it). As the others have said set the bobbin to just support the thread and then increase the needle tension.

I would get the machine going with standard thread and then try adjusting it for the heavier stuff. I would 100% avoid the V92, and even the V69, till you have success with lighter stuff. Guterman M782 strong thread works very well and is strong enough for the work in hand - they have it at Dunelm Mill in Plymouth but ring in advance because they often run out of white. It is an expensive way to buy thread but heigh-ho.

Incorrect threading in the upper works, failure to set the thread in the tension discs and putting the needle in incorrectly are also common problems.

If you have the very heavy, cast iron, Jones machine from the late 60s / 70s it is actually a re-badged Brother and bears a striking resemblance to the Reeds Sailmaker. I had one once and found it was very sensitive to tension setting and I had a lot of the difficulties you have been finding.

 

[wilkinsonsails]

Looking at the top stitch ,you should have a slightly larger needle ,say 120/19 or the next size down 18,that's for v92 thread .This allows the loops to be pulled up and centred correctly .
.The feed mechanism should not be wound down too far either ,as this may retard the stitch formation.Adjust so that you have the longest stitch possible on a domestic.
The check spring may not be pulling up the excess thread ,this will affect the lower thread take up (spring on the side of the tension plates).
Check the thread thru the tension plates, if it pings out , let off the top tension a bit at the plates .The top tension plates can easily get cross thread on the split shaft and not grip the thread.Also check that the lower thread is engaged in the bobbin case spring properly.
The bottom loops are not being pulled up correctly ,so I would finally check bobbin tension too as suggested above .
Oil machine lower works incase it's snagging too .
Happy fiddling ,they can be annoying but it's usually a simple fix in threading arrangements .
Forgot last thing check that you don't have a burr on the end of the needle and it's the right way round with the scoop facing towards the pick up hook .That would break the thread, bobbins wound with uneven tension can cause balling at the needle point ,and make sure that there is some resistance from the thread in bobbin case by arranging the thread to pull off the bobbin anti clockwise.

 

[chal]

Thanks for the suggestions. Just to be more clear, all the loops and extra thread pulled through is on the underside of the material, not the top.

Vic: the bobbin does indeed look like the one in your picture. I had read the FM but it was a bit vague about bobbin tension, just saying something along the lines of "adjust it till you get it right". However, I've tried holding it suspended by the thread as suggested and the tension is enough to hold it. It takes a fair bit of a jerk to get it to drop in fact, which would suggest that if anything the tension is too high on the bobbin. The bobbin thread is not being pulled through the material at all, it's more or less a straight line with loops from above coming through and around. I can't loosen the bobbin tension more than a tiny bit though or the grub screw falls out.

I bought the machine specifically for this job and it was sold as fully serviced though of course I have no way of verifying that.

I have tried 3 different needles in case of sharp edges but it makes no difference.

My best attempt so far looks like this:

upper side, the one you can see as you are sewing:



which looks fine (though the thread broke at the end of this little run). But this is the underside (bobbin side):



Which is a complete dog's dinner. This was done with bobbin thread tension meeting the "holds up the bobbin but the bobbin will drop a bit if you jerk the thread" spec and upper thread tension set to 1. I tried increasing the upper thread tension to 3 and it snapped after only 2 stitches. That's with the V92 which should be pretty strong.

 

[GrahamM376]

Lots of good advice above but there are so many possibilities and you just need to work through them with some scrap material. One additional thing to check is for damage to the gib hook and cap spring, just a slight burr from a needle strike could give the problems you have. Fortunately, my machine (Sailrite) came with comprehensive servicing instructions and illustrations of sewing problems and cures which apply to all machines - if you have someone nearby with one, ask them to print off a copy for you, unfortunately I don't have mine to hand.

 

[NornaBiron]

Advice from Sailrite manual: a tangle on the bottom side of the fabric means there is not enough upper tension. More than likely the thread is not being pulled snugly between the tension disks on the upper tension assembly or is not between them at all. Lift the presser foot (to push the two disks apart) and firmly pull the thread against the centre shaft between the disks. When the presser foot is dropped the disks should close on the thread creating plenty of tension.

Also check the thread take up spring has not broken. I have had this problem before. If this does not solve the problem, check to make sure the tension knob has been tightened sufficiently. I have also found that the tension adjustment knob some times slips on the shaft, I had to reglue mine once. If this all fails check your retaining cap spring. If it has been pierced or damaged all sorts of things go wrong.

Good luck, Ihope this helps. Happy sewing.

Here are a few video links that might help.

https://www.youtube.com/watch?v=JcP59NZXkNM
https://www.youtube.com/watch?v=w2TcJk6PUxg

 

[davidpbo]

When sewing the edge of vinyl with foam backing, I found a walking foot attachment useful. About £8 off eBay. I was using a modern lightweight Janome machine with leather needle.

 

[chal]

Thanks all for the suggestions: tightening the upper tension has already improved matters and I will work through everything and I'm sure I'll get there in the end!

 

[KellysEye]

My other half Jane has made sail covers, awnings and a spray hood with a Sailrite machine, she says it's definitely caused by the wrong tension top or bottom.

 

[Javelin]

I have had similar issues with my Pfaff.
The annoying thing was it only did it on some materials and others it was fine and as said above you just need to work through all the various options.

In the end my solution was to buy a new Hook assembly.
I couldn't see anything wrong with the old one but I'd tried almost everything else.
Found and bought one on ebay and hey presto it fixed the problem.

 

[paul.norton]

You've had plenty of advice regarding tensions etc.

But, have you tried a ball-point needle. When I first tried a bit of sailmaking, the was the first item I was advised to get.


Paul

 

[srm]

I have a "Read's Sailmaker" from the 1970's. Basically, a relabeled heavy duty domestic machine. It has been used to assembled two cruising chutes, rebuilt a number of spinnakers, repair dacron sails and make covers etc. I have never adjusted bobin tension from new; simply adjusted top tension to get a well formed stitch with same thickness of materials that will be used on the job. In my case, once top tension is properly adjusted tangles similar to the photo and breaking threads are due to the needle being very slightly bent, easily cured by a new needle. It's very easy to bend a needle just enough to cause problems when sewing multiple layers of sailcloth.

 

[nigelmercier]

If the bobbin tension can't be backed off so the thread will pull through easily, get a new bobbin carrier, they are only a few quid. You could first check for anything causing it to snag, remove the tension plate and inspect.

The tension on my Sailrite machine should be about "2oz", or as the man who advised me said "like pulling waxed dental floss out of the box". My wife's machine says to hang the bobbin shuttle on the bobbin when doing the drop test, once I ignored this on my machine the results were better.