kgg

My 2 cents worth: Problem 1: Yes I agree oiling first will change the color of the leather however you are going to dye it anyway. The upside to dying first is the dye will penetrate deeper in the leather and allow the dye to go deeper as well. Problem 2: If you convert to airbrushing for both the oiling and dying you will, depending on the size of the piece, get a more even streak free dye covering. Also you will use less oil and less dye in the process. Which method of how you are applying the oil and dye to the leather?? Rag, sponge, brush etc.. kgg

The .3mm thickness is really thin leather. The .3mm would sort equate to about 3/4 oz in leather which is about the thickness of three sheets of regular copier paper. I suspect the problem is mainly do to the leather thickness. With such thin leather it will lend itself to stretching which will throw consistent stitch lengths off and the leather probably is being sucked / forced down ever so slightly into the needle hole of the feed dog as well as along the outside edges of the feed dog in the space between the feed dog and the needle plate opening. I have seen this type of problem with my Juki DNU-1541S when I am sewing thin flexible items as it has a large needle opening in the feed dog and just loves to suck things down that hole. I have used regular weight copier paper placed on the feed dog side of the items with some success in the past. A couple of questions. Which domestic machine are you using, what thread size are you using and what size of needle? kgg

Interesting discussion. I do think it would be an interesting project and would be interested on how it turns out for your application. I'm with @dikman I don't use the needle positioner on the brushless servo motors since I sew slow. I like to keep my setups as simple as possible, brushed servo motor maybe a speed reducer and machine. I do have a couple of machines with the brushless NP compliant brushless servo motor without the NP installed but In reality I can't wait for those to throw in the towel or even a blown fuse so I can justify replacing them with a brushed servo motors. kgg

I don't hand sew but I would think maybe leather gloves something similar to those used for Cycling, Weight Lifting or Wheelchair use would work. kgg

Yes and No. The manuals do show how to wind a bobbin, load/unload a bobbin, what direction the bobbin should turn when the bobbin thread is pulled and what screw to adjust for increasing or decreasing the tension just not how not how to get the tension close to what is needed for a given thread size or what not to do when adjusting the tension screw. Note: 1) Juki LS-1341 can have it's bobbin tension adjust while in your hand and not in the machine and you can do a drop test like a flatbed machine since it is a split case setup. 2) The manuals indicate the bobbin should turn clockwise NOT counter clockwise. Here are three examples from the Juki manuals. Other Brand Name and Clone machines may differ. : i) Juki LS-1341 (compound walking foot cylinder bed)--> threading a bobbin ii) Juki LS-1341 (compound walking foot cylinder bed) --> adjusting bobbin tension iii) Juki DNU-1541S (compound walking foot flatbed)--> threading a bobbin iv) Juki DNU-1541S (compound walking foot flatbed) --> adjusting bobbin tension v) Juki DU-1181N (walking foot flatbed) --> threading a bobbin vi) Juki DU-1181N (walking foot flatbed) --> adjusting bobbin tension kgg

The bobbin is the same it's the bobbin case that is different. Here is a good video on doing a drop test on a flatbed machine. The same applies for a Juki compliant bobbin case on a cylinder arm. kgg

This a typical location for the "tilt stump". Typically just made of plastic, pressure fitted into a hole drilled into the table top and meant as a temporary rest. The machine " slithered off the table hinge and into the drip pan " indicates to me incorrect / damaged hinge and or hinge installation. I have never had a head slip off and with my stubby fingers I am also titling my flatbed machines back to install / remove bobbins. kgg

Downside I think is getting the bobbin tension adjusted. The Juki style is where the bobbin is placed in the top half part of the bobbin assembly, threaded and tension adjusted while still in your hand and then dropped in place. Personally I like being able to adjust the bobbin tension this way as I can do a bobbin tension drop test. kgg

That is correct for the Cobra Class 26 it does not have a Juki compliant bobbin assembly. Here is a video for the bobbin installation. kgg

My two cents worth: Notes i) The recommended size of needle for Tex135 (V138) is a 140 (#22) thin material, 160 (#23) medium material and 180 (#24) thick material. ii) Your 130 needle is really meant for Tex90 (V92). A good reference chart is ( https://www.tolindsewmach.com/thread-chart.html ). iii) V45 has a breaking strength of 7.5 lbs iv) V69 has a breaking strength of 11 lbs v) V92 has a breaking strength of 14.5 lbs vi) V138 has a breaking strength of 22 lbs If I'm not mistaken the 269 is cylinder arm and by adding a simple table top attachment you would have sorta kinda a flatbed for versatility. Personally I wouldn't bother changing the thread size and do all the sewing with Tex135 (V138). kgg

Yes, I have purchased bobbins and bobbin cases for a Sailrite clone. I purchased them from CKPSMS brand and they were decent quality. I have also bought from Aliexpress. kgg

I guess "reasonably priced" is a relative thing. Each needle at $28.57 AUD ($26.23 CAD) and I thought paying $4.50 CAD for 794S size 250 was expensive. kgg

The simple answer is it will not be suitable for leather work. This is a drop feed machine made for sewing fabric at high speeds. kgg

I'm glad you had good success with the dealer. Seems strange, you should contact them or Alder directly for a solution. Ah, you should bought a Juki. kgg

My take: i) Lower startup speed is determined by the amount of bottom end torque it was designed for and how good the electronic closed speed loop controller. Even if you can change the startup parameter to something less then 500 rpm the motor you will introduce some annoying things like stalling, surges and poorer rpm regulation. ii) The cheaper servo motors have 6 internal coils while the better ones have 12 coils which will typically provide better lower startup speed that is more consistent and smoother not just because of the added coils but chances are of they will have better electronic controls. I could not find any information on that particular servo motor but it would be a safer bet to assume it has 6 internal coils or call / email the manufacturer. iii) The only way of getting a reliable slower, smoother startup speed with the brushless servo motors is to install a speed reducer or buy a better servo motor. Getting the 1 stitch per second is probably equal to about 60 RPM. This I think is a bit unrealistic. If you really need that low a speed you would have to build an 8.33 to 1 speed reducer and probably change the servo motors shaft pulley. Keep in mind that an off the shelf speed reducer is 3 to 1 which will give you about 166 rpm. iv) to properly determine a realistic sewing speed you would need to do a pulley calculation knowing the size of the sewing machines handwheel and the size of the servo motors pulley based on the minimum startup speed. kgg

This wouldn't have been my first choice of a machine mainly due to the hole it would punch through the material, 2.5mm diameter unless you are sewing items above 1/2"(12.5mm) in thickness or saddles. I would have probably gone with a Juki LS-1341 or clone with a speed reducer as it would use a smaller diameter needle the system 135 x 16 x needle size for leather. My understanding is the 969 is a class 441 machine that takes the system 7x 3, 794 or 1000 needles (Schmetz). There are needles available for 7x3 or 794 from #19-#27 (120-220) for V92 to V415 thread. I would talk to the dealer to track down the needles if you are going to keep the machine and maybe discuss exchanging the machine for something like a 869 which would take the system 135 x 16 needles . kgg

That is very true there are situations where you just can't get the bobbin thread. Nice tip for machines without reverse. kgg

Thank you Everything in moderation. The aim is two fold. Even tension and to prevent any excess bobbin thread on the underside of the leather or fabric that would cause a problem. kgg

The very basics of getting a good seam are: i) correct machine threading ii) correct top & bobbin tension iii) correct needle system for your machine iv) correct orientation of the needle v) correct needle type (ex. 135 x 16 for leather and 135 x 17 for fabric) vi) correct size of needle to handle the top thread vii) This next step is where people seem to be having a problem. Getting the seam started. You really need to hold both the top and bobbin thread as you start your seam. That can be a royal pain grabbing and holding those threads particularly with smaller sized thread like v69 and v92. If you don't hold both together weird things can happen like jams, bird nesting, skipped stitches, etc. A quick solution is: Tie both threads together by a simple knot. Chances are now you will be able to grab the threads and put consistent tension on both threads at the same time. viii) Locking the threads a) Typical method is sew forward 3 or 4 stitches and then reverse to lock the stitches then continue with forward stitching. b) More Advanced Method is start your stitching 3 or 4 stitches in and reverse sew back 3 or 4 stitches. The seam threads will be locked when you sew forward but with less thread bulk in the needle holes. kgg

To start off. i) Which clone?? ii) What are you trying to sew, Fabric or Leather and how thick? If the machine has a walking foot then the simple answer is a roller foot will Not work. Can you give a little more explanation of your curve / turning woes. A couple of photo's of your setup would help considerably. Also what thread and needle combo are you using??? kgg

Why??? To help speed up the bobbin winding process even further is to have a bobbin being filled while you sew. I always have a second spool of thread in the color and size setup that is dedicated for winding the bobbins. i) install a empty bobbin on the winder, ii) thread the bobbin, iii) engage the winder. iv) bobbin fills as I am sewing v) bobbin winder disengages went the bobbin is full When the bobbin in the machine runs low or is empty replace I replace it with the newly filled bobbin. Rinse and repeat. kgg

I came across a youtube video which I think should be a must view for anyone that uses a sewing machine, domestic or industrial. It helps eliminate the black magic of how stitches (chain-stitch and lock stitch) are formed with a history of the development of sewing machines in very simple terms. Ever wonder why the long grove is on needles?? kgg

What I'm seeing: First photo: i) Stitch length seems different The stitch length seems to be smaller on the right then on the left. ii) Loose stitch on the left. iii) skipped stitch on the right side. iv) Distance to the edge of the binding fold over varies slightly. This probably is being cause by the leather piece either not having a straight edge, not being feed into the binding folder just right, a slight downward pull being applied as the item goes over the backside of the cylinder arm causing a slight shift or a pressure foot slightly off. Are you holding both threads when starting the seam??? Are you using a table top attachment while binding?? It would help in feeding the leather into the binder. As a note I set my binder so it is just leaves a very small space, a couple of mm, between the forward position of the pressure foot and the binding attachment. Any photo's of your binding setup may help. kgg

Couple of questions: 1. How thick is the leather you are trying to bind with?? 2. How thick is the leather you are trying to put the binding over?? 3. What is the total thickness of the edge including the binding. 3. Are you using a 90 degree binder or an inline?? I suspect the problem is that there isn't enough space within the binder attachment to allow for the 5 layers of leather, the edge of the article and 4 layers of binding leather. I have seen this happen when using a basic inline binder and the problem was easily fixed by bending the the top part of binder up slightly and opening the exit end up. If you are using a 90 degree binder the exit end is fixed which I don't think can be modified and the largest opening I have seen is like 6mm. I think using a inline binder would work better or have a 90 degree binder custom made. The problem with the inline is that there are not any that I know off that can be mounted directly to a cylinder arm and none of the table top attachments allow for accessories to be mounted to them like edge guides or binding attachments. Me being me and a cheap geezer I 3D print my own table top attachments to allow for this. kgg

The photo with the nameplate info appears to be for the motor which was made in Croatia. The wording "tvornica elektricnih strojeva subotica" converts to say "Electrical Machine Factory, Subotica". I would send your photo's to USM ( https://usm-americas.com ) and see if they could match up something. kgg