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jfhspike

Needle Timing And A Singer 31-15

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I'm a realtive newbie on working on my old machine.

My 31-15 was working OK for a while, but now it's gotten to the point where it leaves loops on the bottom no matter how high I set the upper tension. It doesn't tend to form rats-nests, though -- just cute little tiny loops through which the bobbin thread passes in a straight line. (And reducing the lower tension to the point where the bobbin-case drops freely (which is too far, I know!) doesn't solve the problem, either.

My thinking (such as it is) is that maybe it's just pulling out too much thread per stroke -- enough that during the "pull it tight" phase after the upper thread's been wrapped past the bobbin, it's just not getting pull up far enough to bury the crossing. While I don't have the entire process of stitch-formation clear in my head, I'll bet that some of you folks do, and can make a guess about what's wrong.

I've looked at the needlbar timing (removed the feed dog to make it actually POSSIBLE to look at it!), and one thing that's not clear to me in the instructions is this: they say that as the shuttle crosses the needle, "the point of the shutle should be 1/16 inch above the eye of the needle." Is that 1/16 above the bottom of the eye, the middle, or the top?

Would raising the needlebar (assuming that I could adjust the shuttle-timing to match) make for less thread being pulled out per stitch? Or am I on completely the wrong track?

Thanks in advance.

John

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Don't mess with the timing unless you are getting skipped stitches. As long as the top thread forms a loop and the pick-up grabs the loop, your timing is fine.

Here are some things to check that could cause the locks to fall under the work.

  1. The top thread is lacking pressure. Check the thread path.
  2. The top thread is not going through the center area of the top tension disks.
  3. The top thread is not going through the slack (check) spring, after the tension disks, before the take-up lever.
  4. The position of the check spring and its assembly has shifted the wrong way.
  5. The check spring is too tight.
  6. The lift lever is engaged behind the machine, removing all tension from the disks.
  7. Something is causing exceptional drag on the bobbin thread. Make sure it really flows easily, but with some resistance.
  8. The needle is too small for the thread knots and density of the material. Move up a needle size and see what happens.
  9. The leather is too dense. Use thread lube, or lubricated thread, or a bigger needle.

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Don't mess with the timing unless you are getting skipped stitches. As long as the top thread forms a loop and the pick-up grabs the loop, your timing is fine.

Here are some things to check that could cause the locks to fall under the work.

  1. The top thread is lacking pressure. Check the thread path.
  2. The top thread is not going through the center area of the top tension disks.
  3. The top thread is not going through the slack (check) spring, after the tension disks, before the take-up lever.
  4. The position of the check spring and its assembly has shifted the wrong way.
  5. The check spring is too tight.
  6. The lift lever is engaged behind the machine, removing all tension from the disks.
  7. Something is causing exceptional drag on the bobbin thread. Make sure it really flows easily, but with some resistance.
  8. The needle is too small for the thread knots and density of the material. Move up a needle size and see what happens.
  9. The leather is too dense. Use thread lube, or lubricated thread, or a bigger needle.

Wow! Thanks for the (very) quick response. I'm pleased to say that I'm with-it enough to have checked almost all of those things. (Yay!) I don't know how to assess #5, but the spring tension seems similar to that on my Pfaff 140 and other machines I've used.

For #7, the bobbin thread seems to have no problems. For instance, when I stop sewing and lift the presser foot, it's easy to move the material away from the foot to cut the two threads.

For #8/9, I'm using V-69 thread, and Sailrite says "Use V-69 and a #16 or #18 needle for fabrics up to six ounces and with Sunbrella". I've got a #16 needle in the machine, and I'm sewing shiny dacron sailcloth (but only two layers -- nothing fancy!)

I'll try a #18, but I was getting exectly the same behavior when I was using V-92 dacron thread and a #20 needle.

It may be too much to ask, but can you explain the function of the check-spring? It's got such a small travel (perhaps 3/8"? Maybe a little more) that it's hard to see what it could be doing.

And can you tell me when, in the stroke-cycle, the "clasp" or "lock" gets pulled up into the material? Is it when the needlebar is at the top of its stroke? When the "thread lever" (the thing the thread goes through after the tension disks) is at the top of its stroke? I can't really figure it out, because it's usually happening pretty fast. :(

Thanks.

-John

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Wow! Thanks for the (very) quick response. I'm pleased to say that I'm with-it enough to have checked almost all of those things. (Yay!) I don't know how to assess #5, but the spring tension seems similar to that on my Pfaff 140 and other machines I've used.

For #7, the bobbin thread seems to have no problems. For instance, when I stop sewing and lift the presser foot, it's easy to move the material away from the foot to cut the two threads.

For #8/9, I'm using V-69 thread, and Sailrite says "Use V-69 and a #16 or #18 needle for fabrics up to six ounces and with Sunbrella". I've got a #16 needle in the machine, and I'm sewing shiny dacron sailcloth (but only two layers -- nothing fancy!)

I'll try a #18, but I was getting exectly the same behavior when I was using V-92 dacron thread and a #20 needle.

It may be too much to ask, but can you explain the function of the check-spring? It's got such a small travel (perhaps 3/8"? Maybe a little more) that it's hard to see what it could be doing.

And can you tell me when, in the stroke-cycle, the "clasp" or "lock" gets pulled up into the material? Is it when the needlebar is at the top of its stroke? When the "thread lever" (the thing the thread goes through after the tension disks) is at the top of its stroke? I can't really figure it out, because it's usually happening pretty fast. :(

John,

Try turning the Hand wheel manually to see what is happening.

ferg

Thanks.

-John

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When the thread take-up lever is at the highest point, the knot is formed in the material.

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When the thread take-up lever is at the highest point, the knot is formed in the material.

50 years, Wizcrafts--

Thanks much to both of you. Your answers inspired me to drag out my Pfaff and watch it in slow-motion (i.e., using the handwheel) until I got a better idea of what was going on in the system. I'm still not sure I'll be able to make the Singer do what it's supposed to do, but at least it's a start!

--John

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John,

So how is it working?I've rebuilt alot of these 31's over the years & alomst all them need a new race in them this is the casting underneath that holds the hook in,it is removed by 2-screws.How much play does the shuttle have?

Bob

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John,

So how is it working?I've rebuilt alot of these 31's over the years & alomst all them need a new race in them this is the casting underneath that holds the hook in,it is removed by 2-screws.How much play does the shuttle have?

Bob

Wow! It's really terrific having experts like you willing to answer my questions. To answer YOUR question: I've replaced the race already, so there's no real play in the shuttle that I can detect.

Here's the current status:

First, I'm not sure I'm making progress, but I'm learning a lot. :)

Second, I'm starting to get blisters on my fingers from turning over the handwheel while the machine's on my workbench rather than in its table. :(

Things I've messed with so far:

  • Just after the take-up spring at the tension disks, the thread passes under a hook (part number 20060, which one manual calls the "thread regulator") and then up to the "thread take up lever" part 12408). That thread-regulator was slightly bent away from the disks, so when the thread-arm reached the top to do it's "tug" on the thread, that regulator was flexing a bit. I straightened it out so that when its screw was tightened, the regulator was pressing against the head-casting and therefore the hook part was essentially immobile.
  • I realized that the tension disks are not really tension-setters so much as tension multipliers, where the base tension is set by that little button about 4" above the disks. (In the parts-diagram I've got, that button isn't shown, but an assembly with three holes -- 52454 -- IS shown instead. I assume the button was a modern improvement or something). The thread was going over that "button" about 90 degrees, perhaps 1/16" from the outside edge of the button, but by removing and inspecting the button aseembly, I learned that it was supposed to pass almost through mid-button, so that a little spring could press a washer against it with a constant pressure.
  • I learned how to extract the take-up spring on the tension disks and re-set it. It seems that you get to set it in units of "one full rotation of springiness". If you simply insert it and move the spring around until it goes where it's supposed to go, it seems to have about, say, 30 degrees of "spring"; the next option is 390 degrees of spring, and so on. I decided to try the 390 instead of the 30 setting, but it had no real impact on my problem.
When I sew two layers of sunbrella, it works OK, but only with the tension disks tightened to the point where I'm running out of threads to screw the nut on. When I switch to the shiny dacron sailcloth, I get the "loops hanging down" thing again. (Just to be clear: when I remove a 4" workpiece, I can grab the bobbin thread and give a good tug and pull it out essentially straight -- it has no "kinks" in it from the stitching -- and the upper thread now shows as a sequence of tiny loops (1/64 - 1/32"?) hanging down from the bottom of the material. When I pull out this upper thread, it's all kinky from having the loops in it, of course.)
Other things I've done to the machine:
  • Cleaned everything I could see with alcohol and q-tips, and then oiled everything. It appears, from the kind of grunge I removed, that this machine had be used on leather in the past.
  • Replaced the tension disks (they were a little rusted on the inside) and spring
  • Replaced the shuttle race and its holder
  • Replaced the needle-holding-thinghy-with-screw (the old one had been torqued by a gorilla until there was almost no slot left in the slotted screw)
  • Switched to a heavy duty needle plate and feed dog
  • Timed the needlebar so that I get no missed stitches
  • Adjusted the feed-dog timing/positioning

Now that I've spent another few hours on this machine, I'm beginning to grasp MOST of what's going on the sequence of operations, at least for the thread-part. The feed-dogs, which seem to be doing their thing properly, and their driving assembly -- those are still a mystery to me, which is fine.

If I get it right, the sequence is something like this:

  1. Needle descends through material. At the bottom-dead-center, it starts to rise. Thread in the groove in the left half of the needle gets lifted through the cloth; thread on the right half, which is pressed between the slippery needly and the rougher material, does not, and the thread "puckers" out to the right.
  2. As this pucker forms, the shuttle-hook enters it from back to front, and pulls a loop of thread downwards and frontwards. This "loop" is provided by the thread-take-up-lever descending, which gives just enough slack to let that loop make it around the bobbin. By this time, the needle has risen out of the material
  3. The loop slips around the bobbin and the shuttle-hook retreats; the loop is pulled around the bobbin (linking it with the bobbin thread!) by the rising of the thread-take-up-lever. At about this time, the feed dogs move the material backwards one stitch-length, so that when the take-up-lever is at its highest point, the material has stopped moving.
  4. As the thread-take-up-lever gets near its highest point, the take-up spring near the tension disks starts getting tensioned; for the last little bit of take-up rise, the tension is so great that the take-up-spring is pulled down all the way, and thread runs direct from the tension-disks to the thread regulator. During the last bit of rise, there's a balancing act: the tension produced both pulls the "clasp" of the upper and bobbin threads up into the material AND eventually gets great enough to pull a bit of NEW upper thread through the disks. That new bit of thread will give us the stuff needed for the next "straight-line" part of the upper-thread in the new stitch.
  5. The process re-starts. As the needle descends, the take-up-spring maintains some tension on the upper thread, so that it lies flat on the material rather than forming a slack loop there. Once the needle-eye meets the material, there's no need for the take-up spring to act further, so it should be adjusted to be slack by this time.

What I don't see is how the balancing act described in part 4 works: why if the the thread tension is great enough to pull the "lock" up into the material, doesn't it pull the lock all the way THROUGH the material? Why does it stop pulling on that part, and suddenly start pulling on the 'tension disk' side? Is the pin in the tension disk assembly (32574) riding on a cam or something and causing the disks to loosen at some critical moment? This is the one part of the sequence that I'm not getting.

In a related question, it seems as if once the material has been moved by the feed-dogs, the take-up-lever applying tension has to pull the thread "around a corner" (the corner being at the presser foot), at least for long sttiches like 1/8", which is mostly what I do.

If I were designing the thing (hah!), I think I'd want to have the feed-dogs act during the DOWNstroke of the needlebar, but presumably that wouldn't make it easy to adjust the amount of thread available for looping-past-the-bobbin depending on stitch-length. Am I missing something here?

Any insight you might have would be much appreciated.

I have one or two questions that I CAN ask coherently:

  1. The "button" -- the first thing the thread passes over after it leaves the "pins" near the handwheel -- has a spring whose tension is adjusted by how far in the button is pressed before it gets screwed into place. Any suggestions on how far in that should be?
  2. Does anyone actually put NUMBERS on things like "upper thread tension"? It'd be pretty easy to say "adjust the tension until the crossover from static to sliding friction occurs at about 4 lbs of force", but I never see this mentioned.
  3. Presumably, once everything is working, I can adjust the upper and lower tension in parallel; if I make both larger, then the stitching will be very tight, and if the material I'm using is something gauzy, it'll end up all bunched up and gathered by the too-tight tension. If I make both lower, then the two pieces of material I'm sewing will be held less tightly against each other, which is probably OK up to a point (esp. for gauzy stuff), but not what I'll want when sewing canvas. So how tight DO I want it? Just short of thread-fraying-and-breaking-during-sewing? Or something else?
  4. The thread-regulator is held in with just one screw, but that screw's in a slot, and the whole assembly can be rotated +/- 10 or 15 degrees as well. Does it matter? What would moving it up or down (which is how the slot's oriented) do to the stitch?

Thanks again in advance,

-John

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John;

If at all possible, could you take some close up photos showing your thread path, from the spool to the needle and a snap or two with the take-up lever and slack spring in various positions and the needle itself?

Are you using the same size thread top and bottom? Is this a #18 needle/#69 thread setup?

If you can't make any more headway on your own, consider sending in to Bob Kovar, owner of Toledo Industrial Sewing Machines. It might be out of time on the top end and he will know that and get everything back into the proper sequence.

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John;

If at all possible, could you take some close up photos showing your thread path, from the spool to the needle and a snap or two with the take-up lever and slack spring in various positions and the needle itself?

Are you using the same size thread top and bottom? Is this a #18 needle/#69 thread setup?

If you can't make any more headway on your own, consider sending in to Bob Kovar, owner of Toledo Industrial Sewing Machines. It might be out of time on the top end and he will know that and get everything back into the proper sequence.

I'll try to get some light on the workbench, and pry the digital camera from my son's hands, and send in photos.

To answer your question: yes, #18 needle, V-69 dabond thread, both top and bottom.

As for sending to Toledo...I've only got about $90 in this machine so far; it might make more sense to give up, and call that the price of learning than to double or triple my costs by sending the thing to Toledo. I might look around for someone more local (Boston, Providence RI) and go ahead and pay for an honest tune-up ... if there actually is anyone local and competent to do the job.

Photos later tonight if possible.

--John

Edited by jfhspike

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This is just a thought, but, test a stitch without any material under the pressor foot, using the hand wheel. As the loop is picked off the eye of the needle (just as the needle begins its ascent), rotate a quarter, or half turn more and see if the top thread pulls easily around the bobbin case. If the top thread is being pinched by inadequate clearance inside the bobbin case/shuttle, the knots will form under the work, rather than in it.

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This is just a thought, but, test a stitch without any material under the pressor foot, using the hand wheel. As the loop is picked off the eye of the needle (just as the needle begins its ascent), rotate a quarter, or half turn more and see if the top thread pulls easily around the bobbin case. If the top thread is being pinched by inadequate clearance inside the bobbin case/shuttle, the knots will form under the work, rather than in it.

Oooh! I really liked this idea, and ran downstairs to test it...but alas, no joy: the top thread slides around the bobbin smooth as can be. (Sigh).

--John

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John;

If at all possible, could you take some close up photos showing your thread path, from the spool to the needle and a snap or two with the take-up lever and slack spring in various positions and the needle itself?

Are you using the same size thread top and bottom? Is this a #18 needle/#69 thread setup?

If you can't make any more headway on your own, consider sending in to Bob Kovar, owner of Toledo Industrial Sewing Machines. It might be out of time on the top end and he will know that and get everything back into the proper sequence.

OK. The first sequence shows the thread path. Pardon my cone-holder; the one in the real sewing table is a little more sophisticated. :) I put some brown sunbrella behind things to make the thread path easier to read.

Second sequence shows 8 equal steps in the operation of the machine, seen from the end. In about step 5, you can see the top-thread coming off the bobbin that it's just passed around.

Third sequence shows the tension spring and thread-take-up-lever in a similar 8-step sequence. Sorry about the bright highlight; I was trying to get things well-lit for this sequence.

--John

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I am NOT an expert as some are BUT I just fixed the same problem on one of my machines today. Make SURE the presser foot is pressing down hard enough. On mine the pressr foot was not going down far enough. it was worn so it was holding the leather down enough to feed good but would let the leather lift a few THOUSANTHS of an inch thus the top thread was not pulled far enough back. Its worth a try. Or change feet to see if that makes a difference. Or if some thing is keeping the foot from going down the last couple 1/000ths.

After studying the pics again I am wondering if the hole or slot in the foot might be to big/wide. and the material is lifting into the hole or slot slightly ( think 1/000ths of an inch) as the thread is being pulled tight. Or the bottom of the foot is not flat and allows the material to lift at the stitch even though it holds it tight behind where the stitch is being formed. All of these can cause what you describe.

Edited by catskin

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I am NOT an expert as some are BUT I just fixed the same problem on one of my machines today. Make SURE the presser foot is pressing down hard enough. On mine the pressr foot was not going down far enough. it was worn so it was holding the leather down enough to feed good but would let the leather lift a few THOUSANTHS of an inch thus the top thread was not pulled far enough back. Its worth a try. Or change feet to see if that makes a difference. Or if some thing is keeping the foot from going down the last couple 1/000ths.

After studying the pics again I am wondering if the hole or slot in the foot might be to big/wide. and the material is lifting into the hole or slot slightly ( think 1/000ths of an inch) as the thread is being pulled tight. Or the bottom of the foot is not flat and allows the material to lift at the stitch even though it holds it tight behind where the stitch is being formed. All of these can cause what you describe.

Thanks for the ideas, catskin. I think you're partly on to something. The material isn't lifting, but the shiny coated dacron sailcloth IS very slippery. And when the take-up lever is at the very top, tugging on both the upper thread at the workpiece and the thread coming through the tension disks, there's a moment when it actually manages to pull the workpiece BACK towards me a tiny bit. That sure suggests that there's plenty of tension there. What I can't figure out is why it's not managing to pull the bobbin thread UP as it should. Unfortunately, even when I hold the work and move it along with the feed dogs so that the backsliding DOESn't happen, I still get the little loops.

I can confirm that the material isn't lifting any more than the sunbrella was lifting -- probably less -- and that the foot tension is quite high -- higher than on my Pfaff 140, for instance, by a substantial amount.

Boy, I'm getting to know this process WAY better than I ever intended to.

--John

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Aw hell; toss in that #20 needle, with #69 thread and see what happens. A bigger hole may help pull the knot up.

For slippery material you may want to consider using a roller foot. That could be just the foot, with little rollers inside, or an entire roller attachment conversion kit. Start with just the pressor foot and see if that helps feed the slippery material better.

If the top thread is pulling the material back towards you, there is too much top tension. Back off some. Loosen the bobbin some more to compensate.

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Aw hell; toss in that #20 needle, with #69 thread and see what happens. A bigger hole may help pull the knot up.

For slippery material you may want to consider using a roller foot. That could be just the foot, with little rollers inside, or an entire roller attachment conversion kit. Start with just the pressor foot and see if that helps feed the slippery material better.

If the top thread is pulling the material back towards you, there is too much top tension. Back off some. Loosen the bobbin some more to compensate.

Brilliant! You guys are awesome (esp. you, Wizcrafts). You pointed me towards the problem, which I should have seen about 10 posts ago.

My thought was "if there's so much tension that it's pulling the piece back, SURELY that's enough to pull the knot up through the material. UNLESS the tension on the upper thread is coming from the pinch between the foot and the material and the throat-plate..." So I tried removing the throat-plate and sewing a couple of inches. The result? Not very pretty stitches, but with the knots on TOP (as you'd expect with too-high top tension).

In fact, the throat-plate I removed was my new one -- a "heavy duty" model that was needed to use a heavy duty feed dog, which seemed like a good idea for working on big canvas (think of a cover for a 35 foot boat -- it weighs about 100 lbs!). That heavy duty plate actually is THICKER than the normal one -- perhaps 1.5mm thicker -- which probably increases the effective presser-foot pressure (and means that the knot would have to get pulled up about 1.5mm more, too!); it probably all conspires to just screw things up (to use the technical term).

I'm betting that a swap back to the old dogs and plate may resolve all my problems; we'll have to see this evening when I'm back from work. But I'm definitely on the right track now. Thanks!

-John

Edited by jfhspike

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It appears that your problem is too much tension presented by the raised throat plate and pressor foot. Have you tried reducing the pressure on the foot? ?? ?????

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It appears that your problem is too much tension presented by the raised throat plate and pressor foot. Have you tried reducing the pressure on the foot? ?? ?????

Yep. I cranked it pretty far down, with no real improvement. But I'll try going down further before I swap the feed dogs and throat plate. I was also considering the possibility of filing a small groove in the middle of one of my spare presser-feet, just wide/deep enough to let the thread slide in it. But I'll only go that route if other things don't work first. (If I were making short stitches, this would all be no problem, I expect. But 1/10" stitches are actually pretty short for the sort of canvas work I'm doing, and after 1/10" feed, the hole is firmly buried under the presser foot.

--John

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Yep. I cranked it pretty far down, with no real improvement. But I'll try going down further before I swap the feed dogs and throat plate. I was also considering the possibility of filing a small groove in the middle of one of my spare presser-feet, just wide/deep enough to let the thread slide in it. But I'll only go that route if other things don't work first. (If I were making short stitches, this would all be no problem, I expect. But 1/10" stitches are actually pretty short for the sort of canvas work I'm doing, and after 1/10" feed, the hole is firmly buried under the presser foot.

--John

If you cranked the pressure spring adjuster "down," you just increased the pressure! Turn it counterclockwise/up. Only apply enough pressure to secure the work between stitches and keep the material from lifting with the needle. A roller foot may be your secret friend in this application.

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If you cranked the pressure spring adjuster "down," you just increased the pressure! Turn it counterclockwise/up. Only apply enough pressure to secure the work between stitches and keep the material from lifting with the needle. A roller foot may be your secret friend in this application.

Sorry -- I wasn't clear. I meant that I cranked the PRESSURE down, by screwing counterclockwise.

Anyhow, here are the results of tonight's experiments:

1. I looked around for another foot, and found the only other one in the drawer appears to be a 1/4" welting foot (I'm only guessing from the shape, of course). The key thing is that there's this big "tunnel" down the middle, hence nothing to pinch the upper thread. Result: Joy! Beautiful stitches. Upper tension something like 3 turns away from "cranked all the way down".

2. Swapped back to regular foot...no joy. Loops prolapsing from the bottom of the material.

3. Changed back to regular needle plate and feed dog (and then spent time messing with adjusting the feed-dog position, because it has to be reset for the different dogs). Set up machine with regular presser foot. Took a few stitches (and inch or two) that looked OK for knot-position, but with the bobbin thread kind of slack. Tried again and...ran out of bobbin thread.

4. Wound a new bobbin. Found that with regular foot and regular plate and dog, at 16 stitches per inch, things look OK. By the time I'm down to 12 per inch, I get loops.

Overall: the test with the welting foot convinces me that the upper thread's getting pinched under the foot, and even very modest presser-foot pressure is enough to cause a problem. Once the stitch-length is great enough with the regular foot, the trapping of the upper thread under the foot starts.

I think that when the stitch-length is too great, the workpiece moves, and it moves back BEYOND the slot in the presser foot -- maybe 1mm beyond. So maybe I need a presser-foot with a deeper slot between the two toes, or need to go with a shorter stitch-length, or...who knows. But with all your help, I feel as if I'm definitely on the right track now.

Thanks again, everyone.

--John

PS: I just noticed that the presser foot I'm using is the most basic possible: it's a single casting, with no "ankle joint" of the kind I'm used to seeing on my Pfaff. I doubt that this is a major cause of problems, but perhaps it's worth considering.

Edited by jfhspike

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Call Bob Kover, at Toledo Industrial Sewing Machines: 866-362-7397. He has parts and accessories for most Singer machines and other major brands. No doubt he has various pressor feet that will fit your machine.

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SUCCESS!

After careful side-by-side comparison of the 31-15 and my Pfaff 140, I decided that the timing of the feed dogs really WAS wrong on the Singer. Basically, the material was done feeding by the time the thread-take-up lever reached the top. That meant that the stitch I was trying to tighten was already "buried" under the presser-foot, and things just weren't working. By contrast, on the Pfaff the feed dogs were at top dead center just about the time the take-up lever reached its top position.

So, after carefully marking the current position of the feed-dog cam (which was pretty easy: the grease on the main shaft was a perfect medium in which to draw a "line" with a small awl), I went ahead and retarded the feed by about 30-40 degrees. Result? Perfection! The stitches look like real stitches, I can reduce the tension by about 2 turns from where it had been, and I can even tighten up the bobbin tension a little without any adverse effects. And when I stitch that sailcloth, it looks like a sailmaker did it rather than a bozo :)

Part of my reason for being willing to mess with the feed timing is that it was clear that it had been messed with relatively recently (less accumulated grease there than on other nearby areas of the machine, and a slightly bunged-up screw-slot was a further clue. I would not, in general, recommend that anyone with a machine that's worth real $$$ try this. I only did it because my machine cost just $50, and I figured I didn't have much to lose.

Thanks again to everyone for helping talk me through this. You guys helped me figure out that if I just reasoned about it hard enough, I'd get somewhere.

--John

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So, I was right when I mentioned that the top end was out of time with the bottom end. This is what I meant.

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So, I was right when I mentioned that the top end was out of time with the bottom end. This is what I meant.

Exactly -- it was that comment that got me thinking, and I looked around and couldn't find any information about how to adjust this "top end timing," so I went with the "maybe it should work like other machines" approach. Thanks again for steering me right.

-John

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