kgg

Nicely done on the 3D printed template forms. My suggestions: On the 3D printed templates. 1) Increase the nozzle end temperature and filament compression. 2) At your direction changes in the template "Cutting" and "Marking" templates at the four corners do a 0.25 mm fillet so the filament is laid down as a radial turn rather then a 90 degree turn. That way the head speed doesn't have to slow down as much to make the turn which will decrease your print time. 3) I would change the "Cutting" and "Marking" from being indented to being raised markings which would decrease your print time. 4) If the bed of the 3D printer is to small to allow you to print say the "Cutting" and "Marking" template as one unit change you design slightly by putting in joining slots or shapes. I would try: 1) cutting the ends of the sandpaper so they join together at say a 45 degree angle. 2) Then super gluing some thin 1" nylon binding tape to the back side of the sand paper so 1/2" is glued to each end. Then the other end is butt ended to the first part and supper glued to the other side of the 1/2" binding tape. That should eliminate the overlap ridge / bump and as it rotates you don't have the whole joining edge of the joint striking the leather at the same time. It may or may not work but maybe worth a try. kgg

Probably because China is such a large market. I know they make the Juki DU-1181n walking foot machine in China. I have one and it is NOT of the same quality as my Juki DNU-1541S made in Japan. kgg

The Juki DSC-246 is made in Japan. Also if you zoom in the nameplate indicates it was made in Japan. kgg

You also might want to check wawak.com for needles 135x16 x size 16 needles ( https://www.wawak.com/sewing/sewing-needles/industrial-sewing-machine-needles/schmetz-leather-industrial-machine-needles-135x16-tri-dpx16-d-10pack/#sku=smnl135116 ). I would not advise you to use a thread larger then V69 with #16 needle. My personal option on the Vinymo thread is yes it can be used in sewing machines but really is meant for those with Class 441 machines like the Juki TSC441 as well as the clones like the Cobra Class 4 and the Cowboy 4500 or the one arm bandits like the Cowboy Outlaw or Tippman Boss to name a few. kgg

What I would do is vacuum the machine with a throated down (1/2") shop vac, wipe the exterior of the machine of with a damp cloth, inspect the internals and if you think there is sand in the internals I would then do a couple of complete flushes of the machine with diesel and then with synthetic transmission oil then wipe dry and oil everything. kgg

From their website ( https://artisansew.com/cylinderarmandpostbedmachine.html ) " Fabrics: 135 x 17 Size(14 to 23). Leather: 135 x 16 TRI Size(14 to 23) " Using undersized needles for your thread my cause problems depending on the thickness and toughness of the leather as the hole the needle makes has to allow for not only the top thread but the twice the thickness of the bobbin thread. If the material is sticky or the needle hole is to small you can get skipped stitches. Here is a good cross reference of recommended needle sizes for various thread sizes. ( https://www.tolindsewmach.com/thread-chart.html ). According to this website ( https://districtleathersupply.com/products/vinymo-mbt-size-5-0-6mm-polyester-thread-full-spool ): Sizing Size 8: Comparable to machine thread size 92 Size 5: Slightly thicker than machine thread size 138 Size 1: Slightly thinner than machine thread size 207 #8 - 0.5mm #5 - 0.6mm #1 - .75mm #0 - 1.00mm When you compare those thread generally accepted thread dimensions to the chart I referenced something is way off. I would strongly suggest contacting both Artisan as the 246 appears to be rated for up to V138 thread and the manufacturer of the thread ( https://nagai--yoriito-com.translate.goog/eng/pages/13/?_x_tr_sl=ja&_x_tr_tl=en&_x_tr_hl=en&_x_tr_pto=sc ) or the US distributor ( www.districtleathersupply.com ) V92 - 0.337mm V138 - 0.414mm V207 - 0.508mm V277 - 0.586mm Also here is a pretty good review of the Vinymo thread from a previous discussion in 2022. kgg

The Consew is just another clone variation of the Singer. Some of the clones use a small needle like thing that you tie the thread to and drop it down the threading hole. If they copied the thread from the Singer, Singer had their own thread pitch and finding them is going to be difficult / impossible. So you can either re-drill / re-tap the holes or use a smaller bolt that will fit through the hole. kgg

I see they added a bobbin winder to the top of the casing rather then off the belt. Great price at $2000 CAD or about $1440 USD. kgg

How good a copy, clone or whatever you want to call them depends on the quality of the casing and internal parts. kgg

Download the Singer 29k-72 manual. Here is a pdf version: kgg Singer 29K71, 72, 73-1.pdf

Two basic methods depending on your interest: 1) Hand stitching, relatively inexpensive. 2) Machine sewing, relatively expensive. Basic New hand operated sewing machine from $1000 USD up and New motorized sewing machine from $2800 USD and up. kgg

Assuming the machines are in good operating condition. As a note the ls-341 is basically an older version of LS-1341. There is a topic that should answer your questions. kgg

I don't think you will ever get a good stitch when the material is .4mm thick and the bobbin thread is .292 thick and the top thread is .292 thick for a total thickness at the knot of .584. I think you would have to down to something like V33 thread. I think the stitch line in the paper versus the fabric has to do with the paper being rigid and the fibers fabric move as the needle enters. The lack of fabric friction, the fabric weave, the thinness of the material and the V69 being UNbonded probably is causing the thread to twist/curl. Try a seam with 3 layers and see what happens. kgg

I wouldn't bother with the belt cover, I find it harder to grip the handwheel and like @dikman said I never install them for that reason. If you really want / need one find someone with a 3D printer and have them print one. I would suggest: i) getting some 1 1/2" plywood, maybe difficult / expensive to get or two pieces of 3/4" plywood and gluing them together. Then gluing a nice laminate to the top of the plywood. ii) dump the clutch style servo motor for either a brushed or brushless servo motor. It will improve your sewing experience particularly with that 3:1 speed reducer you have. kgg

The correct size of needle for Tex 70 (V69) is a size 100 (#16) in thin, a size 110 (#18) in thicker possibly a 120 (#19) in real thick. The correct size of needle for Tex 90 (V92) is a size 120 (#19) in thin, a size 140 (#22) in thicker. Here is a good chart for needle size versus thread size: ( https://www.tolindsewmach.com/thread-chart.html ) I could be mistaken but the PFAFF 545 H4 uses 190R needles to allow for the addition sewing capacity height wise of the H4. Thin materials will always pose a problem as there really isn't enough material to hide the knot sort of like trying to sew a sheet of paper. That combine with an oversized needle for the thread size and you can get funky stitches. kgg

As @dikman said. I think you will be wasting your money on anything with 335 in the model number for your needs. kgg

If I'm not mistaken the sewing capacity of the machines you are looking at is roughly 12mm and you want to sew 15mm. The machines so far are what I would consider similar machines to the Juki LS-1341 or Juki LS-341 sewing capabilities with a max thread size on top and in the bobbin of V138 ( .4mm ) in max sewing thickness. You may sew 15mm occasionally depending on the needle thread combination, the type material and the toughness of material but consistently probably not. To sew 15mm which is touch less then 5/8" really you are into a class 441 machine similar to a Juki TSC-441 or clone. Since you are hand stitching you are probably using .8mm thread which is roughly V554 / T600 / Tkt 5. That thread size will exceed even the Juki TSC441 or clones which can handle V415 (.7mm). Another option maybe a one arm bandit in the Class 441. In that class you have three options Tippman Boss, Cowboy Outlaw and the Weaver Cub but will still be limited to V415 thread. kgg

The 205-64 is a bottom+needle feed machine not a compound feed (feed dog + needle + presser foot). kgg

Just my early morning, coffee deprived thoughts. As a quick test use a back foot that is opposite (back foot with Left side with an open toe center). Then do a the same stitching. If the same thing happens but opposite it's probably a tension issue. I think the it has to do with the amount of presser foot tension being applied in the turn being ever so slightly less on the turn. It might be the also the presser foot being machined slightly off. kgg

Yes I did get the suspended edge guide done for the portable walking foot and used it for awhile. I stripped the machine down of all accessories before selling it. My opinion is that the drop down edge guide really wasn't worth the effort. I did not drill or weld or otherwise make permanent changes to the machine. I would advise not making permanent changes to the machine. I purchased the machine new for $300 CAD, used and abused it, revert it back to original including the original presser foot height settings then sold it for $500 CAD with the table. I just use one of those cheap $20 drop down edge guides off Aliexpress and 3D printed an adapter plate that used existing holes on the machine. I still may have the 3D files somewhere. kgg

Most of the commercially available speed reducers are in the range of 6" (large pulley) and 2" (small pulley). The servo motor belt will connect to the large pulley and the smaller pulley will connect to the sewing machines hand-wheel. You didn't mention 1) the type of servo motor you have brush or electronic brushless. A speed reducer will reduce the existing speed and increase the torque (punching power) 2) the size of handwheel 3) the size of the pulley on the servo motor. The brush servo motors typically have a lower startup speed then a brushless servo motors. An example of the speed reduction: i) size of servo motor pulley: 2" (assumed for calculations) ii) size of sewing machine handwheel: 4" (assumed for calculations) iii) size of speed reducer: 6" and 2" iv) brushless servo motor startup speed: 500rpm v) brushed servo motor startup speed: 200rpm Results: 1. For brushless servo motor: The handwheel speed without a speed reducer would be 250rpm versus with a speed reducer the handwheel speed will be 83 rpm. 2. For brushed servo motors: The handwheel speed without a speed reducer would be 100rpm versus with a speed reducer the handwheel speed will be 33 rpm. kgg

I have done it with a circular saw with a fine tooth blade, a table saw with a fine tooth blade and I have also used a jig saw. I apply 1 " sticky mashing tape to the table top surface and mark the cut line. The tape helps prevent chipping. I then mark and cut the ends the same as the original ends. If the edging has a center alignment / holding wedge as most do I tape the raw edge and mark it. Then using a circular saw I cut a slot deep and wide enough to allow the wedge part of the edging to fit in. I also cut the inside wedging of the edging so it will go around the bend. I do a test fit and either use contact cement or sometimes I use silicone to hold the edging in place. To help straightening and get the edging to around the new bends I will heat the edging with a heat gun. I also completely remove the original edging so when it is reinstalled the two ends meet about center of the back edge of the table top. Sometimes I just forego the original edging and use 1 1/2" metal trim edging that has a small lip. The lip will cover up any chips that may have occurred during cutting the new edge. Just depends on the quality of the table top. The cheaper table tops made with a press board core and thin top skin seem to always want to chip. I have to ask why are you lifting the machine and table top with the motor to your bench rather then using the table frame the machine can with? Are you tight on space??? kgg

Nicely done but how are you planning on winding your bobbins?? kgg

I have never used a post bed machine but this one wouldn't be my choice for a couple of reasons. i) only has 7mm clearance under the presser foot and your stack is 5.6mm. I think you would need your stack plus an extra 3.2mm or 8.8 mm minimum. ii) uses a 135 x7 needle iii) max thread size unknown Why not use a cylinder bed machine?? kgg

Why the smaller bobbin thread??? By doing that you have degraded the strength of the stitch to that of V207. The seam is going to be only as strong as that of the thinner V207 thread. The #24 needle is only recommend for V207 not 277. Here is a good reference chart for needle size to thread size. ( https://www.tolindsewmach.com/thread-chart.html ). Using the incorrect needle size can cause tension problems and the thread being caught in the needle hole which can cause bottom thread inconsistencies. In thicker leather move up a needle size. Sometimes you would use a larger top thread then whats in the bobbin for the visual appearance of the top stitch but using the correct needle size for the top thread. kgg