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

First thing is to figure out what the running length of the dies you want to use, thickness of leather and the necessary tonnage required to punch the die through. A alternative to a clicker press be it slower that may work is a hydraulic press. A 20 ton press will cost about $250 USD. kgg

Very nicely done. kgg

I don't think you are going to get the bobbin winder installed with the motor and reducer pulley mounted on the top of the table. My approach would be a more conventional method of mounting the motor and speed reducer on the underside of the table top. Cut a long slot probaly about 6" long for the machine belt directly below the sewing machine handwheel inline with the belt pulley part of the handwheel. The belt would be straight down through the table top to the small pulley of the speed reducer. The bobbin winder would be then installed pretty much as it was before installing a speed reducer. Once you choose which way you want to approach installing the speed reducer either on top of the table top or below and you have the speeder reducer installed. I would take length of string and wrap it like a belt would be around the pulleys, measure the length and add 2 inches to get the length of the belt needed. kgg

My take/ opinion so take with a grain of salt : 1. The Cobra is just one of many clones based off the Juki LS-341 except my understanding is the Cobra is a hybrid clone using another type of bobbin assembly rather then the Juki assembly. Most clones come from China or Taiwan. The Juki LS-341 and the newer Juki LS-1341 are made in Japan. 2. Some clone machine vendors have a tendency to rate the thread capacity of the machine on what size of thread can be stuffed through the rated needle. Juki rates their machines on what the max size thread used as a top thread as well as same size of thread in the bobbin that can be used at max sewing thickness. 3. On the used Juki LS-341 inspect the machine carefully for worn out /rusted/ cracked internal parts like the main drive belt and wear on the guides / tensioners. There are a number of used machines that are imported from overseas factories so be careful. 4. Two layers of 8 oz is about a 1/4" and depending on the thread / needle combination and the toughness of the leather either machine should handle that. 5. If most of your work is for wallets/belts (flat type work) a flatbed machine maybe a better option rather then a cylinder arm machine unless you purchase a flatbed table top attachment for the cylinder arm machine. Since you presently handstitch items if you are looking for similar thread size thickness none of the Class 341 / 1341 or even the Class 441 will come close. 6. It is kind of difficult really to compare a used Juki LS-341 to a new clone machine. There are just to many variables related to condition/maintenance/etc. The Juki LS-341 hasn't been made in years and was replaced with the Juki LS-1341. If the machine is going to be used in a production environment 8 hours a day, 7 days a week then spend the extra money and buy a new Juki LS-1341. That will set you back about $5000USD. If it is more for a hobby use then most people will purchase a clone machine for about half that cost. kgg

Are you sure, me thinks you are an addict... just one more machine, just one more attachment. kgg

Just to add another twist to the conversion. If hardness of the burnish wheel is an important factor what would the drawback or pro's to using a metal burnishing wheel with machines grooves like the wooden ones??? Steel, Aluminum, Brass kgg

It is an attachment for plinking. Here is a link outlining it. ( https://www.ebay.ca/itm/351741810267 ) kgg

What size and type of thread are you using?? How thick of leather are you trying on sewing??? What size of needle are you using??? kgg

The .8mm thread size is roughly equal to V554 thread so there is really only the Juki TSC -441 and clones along with the one armed bandits that can come close to that thread size. As a comparison V138 thread is about .4mm. If thread size is a main factor the machines you highlighted will not work. kgg

I am not sure but that thread I think is just polyester not bonded so it may give you some problems related to like lint buildup. I would recommend: i) Purchase the 1lb spools of whatever thread you decide to purchase it will give you less spring back / coiling problems then the smaller 8 / 4 / 2 ounce sizes. ii) Purchasing two 1lb spools that way you can have one spool for winding bobbins as you sew and the other one for the top thread. That way you don't need to un-thread the machine just to wind a bobbin. Some like what I done with my Juki DNU-1541S. iii) Use bonded polyester or bonded nylon thread from a brand name manufacturer rather then the cheap Chinese stuff. kgg

When I clicked on the link you supplied it appears as the correct needle for a system 135x16 needle for a size 110 needle. The size 110 is for V69 (40 metric) thread. What size of needle did you order for what size of thread you are planning on using? Also what is the thickness of leather you are planning on sewing? kgg

Here is a screen shot of the spec for the Juki DNU-1541 series: My understanding is the system 135x8 is not designed for walking foot machines made for drop feed machines. It is a slightly shorter needle which may require you to adjust the needle bar as well the hook to the needle timing. Needle selection reference: The Thread Exchange by Juki model ( https://www.thethreadexchange.com/miva/merchant.mvc?Screen=CTGY&Category_Code=needle-systems-juki ) The equivalent to a system 135 needle for leather, 135x16, is the DPx16 and 135x1 NRTW. The equivalent to a system 135 needle for fabric, 135x17, is the MR, 3355 MR, DPx1 MR, DPx17 Why not use the correct system needles recommended by the manufacturer, needles are cheap and save yourself the problems / headaches associated with other then recommended needles. kgg

No, do NOT use a system 134 needle for the Juki DNU -1541 and Juki DNU-1541S they are made and setup for a system 135 x 17 x (needle size) for fabric or 135 x 16 x (needle size) for leather, check you manual. Here is a good reference chart for needle size vs thread size. ( https://www.tolindsewmach.com/thread-chart.html ). I would also suggest: i) reducing the presser foot pressure as it appears the pressure foot is imprinting the leather needle plate hole into the leather. ii) increase the bobbin tension using the drop method of setting the bobbin tension. kgg

I will PM you.

Photo 1: i) Tells me it was used in a factory setting with little or no maintenance, the timing belt is cracked and is on it's last legs. The machine needs to be properly flushed out to remove any debris so it can be determined what else needs or potentially needs to be replaced. ii) missing presser foot lifting mechanism iii) missing base gasket and cylinder arm oil drain cotton cord Photo 2: i) Tells me someone replaced the main tension assembly and possibly the bobbin winder. ii) Top thread guide pin missing Photo 3: Shows a lot of discoloration / wear on the nose. Photo 4: i) Missing chrome cover plate on the front of the head that covers the lifting mechanism. ii) In the background of the fourth photo I did notice a second Juki LS-1341 on a dolly. My bad mind tells me this is a fresh off the boat from an overseas factory setting and shipped in. Did you ask where the machine came from? Personally I don't recommend buying an ex factory machine. EX factory machines are gotten rid of for a reason unless you are prepared to do any possible repairs yourself and the price is dirt cheap. I would suggest you keep looking buying a good used machine from a hobbyist or buy a new clone from a reputable dealer. Some others maybe better able to suggest a dealer close to you but you have not included your location. kgg