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Hi, recently i bought a Pfaff 345-3H (i’m not 100% sure but it looks like a double needle version of the Pfaff 335) and it worked fine. I’ve done a few projects with it and so far no problems. I did not do anything in particular for as far as i can remember but now both bobbins are rotating and skipping stitches(i guess there is not anything broken with one because both have the same issue). I’ll try to explain what is happening but please see video link below. The loop of thread around the bobbin gets stuck between the bobbin case and the thing that keeps the bobbin from rotating (i don’t know how this part is called). The thread loop stops and gets pulled trough with a click. It looks like that is causing the skipped stitches. Sometimes the whole bobbin case gets pulled with the threat and the case makes a full turn and gets tied up. According to the video in this thread i found https://leatherworker.net/forum/topic/85248-please-help-thread-is-too-tight-when-pass-bobbin/ the bobbin case should not be rotating and the stoppy thing opens and closes in the right time to let the thread pass. I’m not very experienced with leather sewing machines but i searched a lot and could not find a solution. At this point i’m not even sure if the bobbin is supposed to be moving or not... Any ideas on what causes this and how to fix this? Forward thanks! Video of the problem:

I've been searching the site for a manual and finding lots of parts list. I have found some links to repair manuals but they are pretty hold and won't come up any longer. Any help is greatly appreciated.

Need some advice please... My Pfaff 145-P-6C sews beautiful until it skips random stitches. Usually in prominent locations! Leather material used is 3 - 5 oz in weight, thread 69 top & bottom, needle 190LR - 125/20. Tried a larger needle with same results. Machine was recently serviced, no issues noted. It has been around a while used hard in a canvas factory. Any suggestions on what to try as I am very frustrated. Thanks!!!

Here's the story of a Singer 29-4 sewing machine repair, for a machine that is skipping stitches. I'm writing it for someone who follows after me that may not have much background in repairs, and may have a machine as worn out as mine, so descriptions are as simple as I can make them. I've been trying to figure out why the Singer 29-4 machine skips stitches. I was given this lovely old industrial treadle machine, and except that it moved a little stiffly, it mostly sewed ok. It only rarely skipped stitches, until the day I oiled it. No kidding... the old gunky oil must have been all that was holding some of these parts in alignment, as after oiling it moved really smoothly, but began skipping stitches like mad! What a shock! I didn't even know this was possible! Now this machine has seen a lot of wear, the insignias are completely worn off it, and it's been used to sew leather most of it's life. It dates at 1907 I discovered when I checked in with it's Singer serial number on their site. I wanted it to sew right. I messed with tension hoping that might help, but no help was had there. I verified that the needle was right for the machine, and the thread weight was right for the needle, the needle positioning was correct and then in frustration started the search for the manuals, the repair books, support forums, blogs, any place I could glean information. (many thanks to Wizcrafts for his postings on this machine) I got one good lead that the almost invisible black T shaped flat spring on the left side of the needle bar just below where it enters the body of the machine, was likely to cause skipped stitches if it was loose. Mine was loose, and with high hopes and a gentle hand, hoping against hope that I wouldn't break that little guy, I remedied that problem... but no... still a lot of skipping, big areas of an inch or longer would be left un-stitched. Feeling frustrated, I searched more. This led me to examine the timing, and after a lot of work with it, I realized that there are not more variations in how it can be set up... you simply cannot move the teeth on the rack to one side or the other without the rack either hitting the stops on the metal gear below the bobbin case, or failing to engage the second gear properly, if you move them even one tooth in either direction. Someone suggested that this placement of the timing rack could be changed, but on my machine, there appears to me to be only one way to set it up. If that gear below the bobbin case went all the way round in a circle with it's teeth, you could maybe move the rack over or back a tooth, but since it has only 3 teeth, when you slide the rack over, it either hits metal at one end of it's travel, or the second rack hits metal on the other end of it's travel. I took photos of the correct positioning, and will save them... not sure how to include them on this forum, but will try to imbed them into this message. For an inquisitive person, the timing racks and gears don't want to be looked at unless you first remove the machine from it's base and tip it back flat, before taking off that cover under there. Otherwise, all pieces will be on the floor, and you won't have clue where they went. So next I looked for slop in the bobbin action, and there was plenty there, nearly 1/8 inch of slop. I thought I might have to deal with new parts underneath, the gears and the racks that drive the bobbin shuttle, however I was hoping that it might not require this. So after more reading I also thought to check the amount of play in the needle bar. It had some side to side play of about 1 millimeter at the tip of the needle. I discovered that the second screw on the bottom of the needle bar, actually detaches a chunk off the bottom of the needle bar that holds the needle. All my newer machines were one solid piece down there, but this guy is made in two pieces,and the screw that doesn't hold the needle but is right near there on the needle bar, will allow you to position the needle side to side in relation to the bobbin shuttle. You can get it close enough to rub the bobbin shuttle case, which is too close, and then back it off just a hair and tighten it down. When adjusted properly, it appeared to send the eye of the needle right down beside the hook, ... but still the machine skipped stitches. Drat! Back to the homework of searching and reading. The real kicker for me turned out to be when I found the tip to examine how much up and down play was in the needle bar. I had a friend hold the hand wheel steady, and found that when I pushed up firmly on the needle bar, it went up maybe about 3/16ths of an inch, clearly way more than it should. I reasoned that when the needle hit a stiff piece of leather, instead of coming through, that slop would cause a serious delay in the downward progress of the needle, and the thread going through the eye of the needle would come down too late to catch on the passing bobbin shuttle hook during sewing. Even though it looked good in terms of placement when just moving it through it's paces without any leather in the machine, once the leather was there it would throw off the timing .... hence the skipping of stitches would only show when under load. Some information about the little silver guide wheel that travels in the track on the inside of the hand wheel led me to examine that, but it didn't seem overly loose, just a little bit worn. Upon closer examination I found that the big knuckle with it's attached pin which is at the top of the needle bar, and which fits into the end of the long rocking arm which comes across the top of the machine, had worn an oblong hole, and that pin was very, very loose in that hole. (I think the name of that part is Needle bar piston joint, and I am certain it is part number 8588 on plate 1032 of the old parts list.) I considered replacing the part, but what if the problem lay in the hole that the part rides in? A close look revealed that all the years of pounding through leather had caused excessive wear on the top of the hole where that pin slid in and out. I noticed the pin movement in and out was only about half an inch so I thought I'd try a shim in there to take up the slack, experimentally. I made a shim of brass, using brass shim stock that was .005 inch thick. Shim stock metal can be bought at most good hardware stores, and mine came in a little sheet of 4x6 metal. This shim I just cut with scissors about 3/8 inch wide and a couple inches long. I curved it a little bit so it would follow the curvature of the sliding pin, then with some futzing, I worked it into the gap at the top of the pin, (right there below the take up lever that guides your thread), sliding it gradually into the gullied out hole along the top of the pin until it was in there about 3/4 of an inch deep. I tried gently turning the hand wheel to see if it would stay in place, and it was somewhat daunting because the movement of the arm on the pin was a little stiff, however I put some pressure on it and after a moment it seemed to slide ok. The in and out movement had to be repeated a few times, and I also had to use a little screw driver tip to try to smooth the shim out over the top of the pin right up to the knuckle and make a sharp 90 degree bend upward in it to get the excess length out of the way. I eventually found I could fold it back over the top of the big black rocker arm, and actually tape the excess onto the rocker arm, so it was held in place, while the pin slid in and out below it. Being as my machine is black, I used black electrical tape, just for appearances sake. I'd hate to admit to anyone that my machine was held together by duct tape!... though to be sure that would have worked perfectly. Here's a photo of the shim folded back and taped in place... if it comes through on this forum. The movement of the arm was stiff for about three or 4 turns of the hand wheel as it flattened out the shim stock inside the hole against the pin, then it settled into a smooth movement, and I tested the needle bar up and down movement again. Almost no movement now... oh boy, let's try to sew something! I rethreaded the machine, took up the leather again, a double thickness of 1/8 inch leather, and started stitching, first by hand gently with the hand wheel, then got my courage up and used the treadle. It was catching properly! Nothing I could do would make it Not catch properly. I sewed little circles, I went all over the place! I adjusted the top and bottom tension... perfect! So even though there still is the side to side slop of about 1mm in the needle bar, and even though there is still a lot of slop in the shuttle movement, that one shim has completely set this old machine to rights, and I can sew again! I can't say how long that will last, and as I am only an occasional leather worker, making my own sandals and work boots, I hope it will last well enough to keep me going. What was significant to me was that this One shim was the real area where it was important to take up the slop. No doubt more could be done with further parts replacement, but for those on a sensitive budget, it's nice to know that it might be possible to resuscitate an old machine with just this one very inexpensive fix. This success made me really happy!! I'd be happy to send photos to any who might find it helpful. Roberta (in Northern Idaho) as i reach the end of this post i notice there is a place to add photos. Both the timing photos are correct, one is just at a different position in the shuttle rotation. the other photo of the completed shim job.