Gymnast

The sudden change could be, that the needle changed height by the needle is not sufficiently fastened or the fixing of the needle bar to the crank shaft is loose. So I recommend that you check the height of the needle bar. Have you got the service manual? The other thing to do is to remove the shuttle hook and clean this area for possible remains of thread. The shuttle hook always need good lubrication at its race. You need to use leather point needles as Wiz already wrote.

Thank you for the moved post and answer

Thanks. I did not know about this trick. But then Google helped me to look it up, and it did not show up that many places. I found it here by Bernina: https://blog.bernina.com/en/2023/02/sewing-needle-and-thread/ I tried it on some known threads, and I think it will work to discard too small needles. My 207 thread and 140 needle was on the edge. But Google directed me to this other similar method as well proposed by Groz-Beckert: https://youtu.be/4fsQGtMSFEQ?si=2CGPJffRur3sgU8x&t=121 I think this method will accept too small needles.

I am just confirming the remarks by others. Something is wrong, when the hook hits the needle like that. Make sure, that you do not use a bended needle. It could also be the presser foot or feed dog that push the needle towards the hook. You should also make sure, that the hole in the presser foot and feed dog got sufficient size to the needle size you use. I think the machine manual should inform you about that. For my machines I got almost all sizes of needles, so I am able to alter them for different threads and fabrics I sew. The right needle size for V207 thread is above 140, but I have sewn some vinyl with a V207 polyester thread and 140 needle, so it is not like it should be impossible. It do also help to use leather needles for leather. The thread manufacturer will normally provide you with information about the right needle size. This is an example of that: https://www.amann.com/products/product/serafil/

In connection with my experiments with making a DC motor drive, I had the opportunity to measure the motor current consumption for a sewing situation. For DC motors, the current is close to proportional to the delivered shaft torque. I'm fine with getting some measurement results with numbers on some situations to get a better understanding. But for normal users I don't think it has any relevance. Maybe the knowledge can be useful if you want to experiment a bit with which motor you want on a sewing machine. The curve below shows the DC motor current over time for just above one stitch. The driver electronics ensures a very constant motor speed. This video shows the current situation used when the power consumption was recorded: https://youtu.be/N-FB2jHYyuw The measured mean torque here is approximately 0.5 Nm, while the maximum torque is approximately 2.3 Nm. This corresponds to a peak pressure on the sewing needle equivalent to 145 N (15 kgF or 33 lb). For these slightly more powerful household sewing machines, I use as a general rule to limit the torque to 3.5 Nm. My guess is that industrial sewing machines for leather can generally withstand a significantly higher torque. At higher speeds of the sewing machine, you will be able to get help to penetrate the material by taking the energy from the inertia of the motor and flywheel, which then briefly reduces speed. At low speeds of the sewing machine, there will typically not be enough rotational energy for it. I guess that for larger leather sewing machines you will also see a correspondingly large variation in the torque that the motor must supply to the sewing machine at low speeds. If you want to know more about the specific setup with this Pfaff 230, there is more information here:

Thanks. Yes, I guess the CB-bobbin allows for thicker thread, but the 201 actually was able to handle this thread as well. I guess, that when you compare a Singer 15-91 and a 201-2 in the US, that have got the same potted motors, then you will find the 15-91 to be better, because the 201-2 require more torque from the motor to operate thicker threads. TonyGreen is from UK, and these machines are belt driven machines in Europe (with few exceptions). Belt driven machines got more possibilities for changing the motor power or using speed reducers. I agree with the Northmount and Wiz, that a walking foot machine is better for leather and jobs like this. But TonyGreen asked for advise on smaller household machines, and some of them can do some jobs too, if you modify them.

Hello kgg My YouTube channel got some more videos with this sewing machine. This is a speed test with some remarks using the original motor: https://youtu.be/VLU_s1RGasA This is more about the mechanics regarding the new DIY motor drive: https://youtu.be/Ig69cM_0w7Q The pedal is like you see and attached to an air pressure sensor. Some electronics and an Arduino microcontroller is involved as well, but I have not yet made any "nice" documentation of that yet. To my knowledge, the important thing about the pedal is, that you need to have a large range of pressure applied from minimum speed to maximum speed of the machine. I use a pressure of 4 Newton (0.9 pounds) for minimum speed and 40 Newton (9 pounds) for max speed. So you got a factor 10 in pressure needed that allows for precise and fast control by the foot. The possible length of compression of the pedal have much less importance. When you using air as I do, you will have have a pressure change due to temperature changes (ideal gas law). Therefore a zero point adjustment are needed by some manual setting or by some software (I use software here). Furthermore the software implement some unilinear function, so you can get more accurate low speed control. I use parts of a parabola function. You are welcome to ask for more specific details, and I shall try to provide them.

In my opinion, the Singer 15 and 201 got about same performance. I think the Singer 15 is close to a Pfaff 30, and I have tried to make a comparison of a Pfaff 30 and Singer 201 with this video for heavier work: https://youtu.be/u2D2DEKtgFQ I think the possible limitations for the standard Singer 201 or 15 is the lack of low speed control and its possible max reliable thread tension. So you may look into doing a few modifications to the Singer 201, like making a speed reducer and using a heavier tension spring.

I bought a Pfaff 230 about a year ago. It is a somewhat heavily built household sewing machine and can be considered a bit like a little sister to the Pfaff 138. Where household machines have typically been sold with motors with a maximum shaft power of 40 W, the Pfaff 230 was sold in Denmark with a larger motor with a shaft power of 80 W, which could make them sew at a maximum speed of approx. 1900 stitches/minute. According to German sources, the machine can withstand speeds of up to 2500 stitches/minute. Today's typical servo motors for industrial sewing machines have an input power of 550 W and a maximum shaft power of around 350 W. Since I don't have room for a fixed table with a regular servo motor, I decided to build a smaller motor drive from scratch as a little DIY project to see what could be achieved. But at the same time cheap components were used. The idea was to achieve a wide speed range, and the result was that the difference between the lowest possible speed and the highest speed became a factor of approx. 600. Lowest speed was 2-3 stitches/minute and highest was 1780 stitches/minute. Most available servo motors that you can buy have a minimum to maximum speed ratio of about 50. Most users here will probably think that the speed ratio of 50 is good enough, but maybe they haven't tried anything else. The reference may be the old clutch motors, which were more difficult to control. Here, for example, a seller who describes the sewing machine's lowest speed as super low: My assessment would be that the lowest speed here is far too high. At the same time I don't like how the machine jump-starts with no warning. This is a video with a demonstration of my DIY motor drive: I have now tried using the machine for a few projects, and I think the low possible speed is an advantage. This means that you get full control of the needle position via the pedal. A good pedal is also necessary to be able to achieve this. At the same time, the sewing machine can also sew quite fast.

I have studied a Pfaff 230 regarding the check spring motion. It is actually engaged four times each stitch. Can it be right? I think the machine works with no problem, and it sews with a max speed of 1825 stitches/min with a Tex 70 polyester thread with 4 mm wide zig zag in a 2 mm thick cotton webbing. The needle size is 120/19 with this task. The check spring stroke is set so it correspond to 11 mm motion of the needle thread. The tension of the check spring is set to 0.25 N (1 oz) at the point it engages the thread. This check spring tension setting is significantly higher than it was when I got the sewing machine, but this higher tension "feels" right to me. The clearance at the position finger bracket have been checked. The check spring is engaged when you have some tension in the needle thread and no thread slack. I made a video with the handwheel very slow turned, so you can see how and when the check spring is engaged: https://youtu.be/3vZr0fmwNsU The four times the check spring is engaged, seems to be caused by this: 1) The thread has been pulled down in max length and is around the shuttle. 2) The thread may be catching something at the hooks or shuttle, that shortly require some tension to pass. 3) The thread require some tension to pass the position finger bracket. 4) The take-up lever tightens and forms the stitch with the higher thread tension from the tensioner.

I have seen ISO 68 oil specified for some sewing machines as well. The number here refers to the viscosity at 40 C. You can get the same kind of white mineral oil up to ISO 150. Motor oil got some more additives, that you do not want in a sewing machine, and it typically have got a viscosity of about 100 at 40 C. A higher viscosity will make the bearings carry the load better at lower speed, but the loses and heat up of the oil may get unacceptable for higher speeds. If the machine have got an oil pump and some centralized systems to distributes oil around, then you should stick to what the manufacturer recommend. I use some ISO 100 oil in two of my vintage sewing machine, that I use for heavier loads and for lower speeds than it may have been designed for. The machine would normally use ISO 22. It is no big deal for you to alter the oil type with respect to your use of the machine.

Do you know of suppliers of very long upholstery needles longer than 0.5 m or 20"? For some odd experimental project I like to try to use such a needle. It needs to have a needle eye and one sharp point end. I guess, that it needs to be at least 2 mm in diameter and made of a piano-wire kind of steel. Do you know of suppliers of such long needles in North America and in Europe? I found this supplier of a 24" needle in Arizona: https://homesewingdepot.com/products/upholstery-needle-24-11-gauge?variant=32770271685 What size is a 11 gauge needle?

Now I have put a few numbers of sewing again... I know, that more experienced people here already have told us, that the same type of thread from a thread manufacturer are different. Different by color and different by batch. I did not think. that it mattered that much for the bobbin thread tension, but when I could not repeat the balanced stitch from some previous notes I tried to measure a bit more. It was a Amann Serafil polyester thread Tex 135, and for the same setting of the bobbin thread tension spring I got these measured bobbin thread tensions measured by a spring dynamometer: White: 0.5 N (1.8 oz) Black: 0.6 N (2.2 oz) Blue: 0.75 N (2.7 oz) This is a video about how I measure bobbin thread tension, but I guess many of you have already seen it: https://youtu.be/kINRgj42GnI

If you have looked the news recently, there have been a rapidly rising global concern regarding PFAS in the environment. Nine states in US have come up with strict restrictions on PFAS in products. EU is still talking about it for a long time. So I think everybody in our business needs to think about, what we use, and try to avoid products, that contain PFAS or creates PFAS when produced. Factories that produce PTFE (Teflon) are leaking PFAS to the environment. I know that we got lubricants for sewing machines, that contain both PTFE or PFAS like Triflow. We also got some fabrics and sewing threads with PTFE in them. I noticed this note regarding lubricants: https://www.ri.se/en/there-are-no-justifiable-reasons-to-use-ptfe-in-bike-lubes

More things can cause skipped stitches. I remember a video by Uwe, on a Juki 441 class machine that can have a problem with skipped stitches in reverse. Perhaps it can help: