kgg

Yes those machines are all manual machines. Singer no longer and hasn't for many years made industrial sewing machines that I'm aware of. This narrows the field down for sewing machines. If you only want one machine a sort of all rounder machine would be a cylinder arm machine with a flatbed attachment. You can do items that are best done with a flatbed sewing machine (example: wallets) as well as items done with a cylinder arm that are circular. Then there is the dollar factor. Depending on how thick your leather will be including the seams an excellent machine would be a Juki LS -1341 or a clone machine. The Juki LS-1341 new will cost about $5200 USD while a clone of the older Juki LS-341 will cost about $2500 USD. Juki is the typical machines that the clones copy. So accessories like binding attachments and parts are readily available at reasonable prices. Then there is the used market for both brand name and clone machines which can be had from either a dealer / repair shop or the owner directly. I would suggest getting one from a dealer that has been gone over unless you or you know someone that can properly evaluate a used machine. The only thing is the footwear part of what you want to make as this has a very broad range from slippers to workboots and everything in between ????? kgg

I would definitely investigate getting a machine particularly since hand stitching will probably aggravate your arthritis. My mother use to love to sew all sorts of garments, hand knitted everything from socks to heavy real wool sweaters and use sign language for her day job. When she turned about 50 her arthritis got so bad she could hardly sign anymore let allow sew or knit. My advice is put the needles down and get a sewing machine to reduce the stress on your hands. Determine what items you would like to sew and what items you eventually would like to sew and purchase a motorized sewing machine accordingly. I think the one armed bandits like the Tippmann Boss ($1000 - $1575 USD) , Cowboy Outlaw ($1400 USD) and the Master Tool Cub by Weaver ($2000 USD) will also aggravate your arthritis but not as bad as hand stitching will eventually. I look at the bottom rating reviews for items, the ones giving the bottom end reviews. I think those probably give a more accurate view of what to expect. kgg

If you enjoy hand stitching you still can do that it for your own or special projects but when doing large quantity projects mechanizing the work process is the way to go. To me it's like hand sawing versus using a circular saw, one piece of 2x4 no big deal but a 100 I'll use the circular saw. Doing those sheaths all by hand will I bet quickly lose the enjoyment of doing that many similar items. How mechanized you want or can afford will be the question. Just adding a proper sewing machine will as @Dwight mentioned from however long it takes to hand stitch to about five minutes for sewing as will as reducing the hand and mental fatigue. kgg

I would figure out i) an average cost for materials like leather, dye, thread, etc including wastage ii) an average time to complete a knife sheath from cutting the leather to the finished sheath iii) a fair hourly rate you want to charge iv) a profit margin Just as an example would be $10 for materials plus $15 hourly labor rate (say 1 hour to just to keep it simple for the math) plus say 40 percent for profit for a total: $25 for labor / materials plus $25 x0.40 = $35 per sheath. The only two areas you can really save on the cost per sheath is the labor cost which could be reduced using equipment and the profit margin. kgg

Have a look at this video of the Consew 226 being converted to the larger bobbin it should answer you questions and the parts you will need. kgg

If I had to choose I would go with the possibly a Juki DNU - 1541S for thickness and material you noted. The Juki LU-1508-NH and the Dürkopp Adler maybe to heavy a duty machine for the task. i) The Juki and the Dürkopp Adler are brand name machines which when you decide to sell will command a better resale price. ii) Dürkopp Adler parts and accessories are generally expensive. iii) Juki both parts / accessories are fairly inexpensive and realty available. If I'm not mistaken 2 layers of 18 oz vinyl would be 1.01 mm thick and 2 layers of 18 oz canvas would be 2.13mm for a total of 3.014 mm so maybe a Juki DNU-1541S would be an appropriate sewing machine as the thickness is well within it's sewing capacity and a lot cheaper then either the Juki LU-1508 NH or Dürkopp Adler. That said I would take a sample of what you are planning on sewing and visit a dealer(s) to try out various machines so you can make sure the machine you select is the right machine for your needs. kgg

If you decide to re-drill and re-tap the hole be aware that Singer was notorious for using their own thread pattern on screws. Be prepared to drill and tap for a standard thread pattern and use a readily available screw with either metric or imperial threads in the correct length or as @nylonRigging use a nut and bolt. kgg

Looking at the photo of the thumb nut it appears to me that the body is split as the result of someone at some point screwed the thumb nut in to far. My suggestion would be to remove the center screw and the part the center screw screws into. With those items removed you should be able to unscrew the thumb nut from the threaded rod. Those threads inside the thumb nut are probably striped or cross threaded. You are more then likely going to have to replace the thumb nut with a new one. The installation of a new thumb nut may solve your stitch problems. kgg

I think the repair shop installed a 190 needle system needle which I think is what is recommended for the H4 sub class and the 134-35 are for the H3 subclass. The 190 needles are about 1/4" longer so the timing will not be correct. The needle needs to be installed so the two groves on the needle are on the left and you thread the needle from left to right completely opposite to a domestic sewing machine. The stitch length is changed by turning the thumb nut on the lever. Here is a manual for the PFAFF 545 the manual covers models from 141 to 545. kgg 545.pdf

Any industrial sewing machine repair shop probably can do this but the general conversion project will require: i) the timing belt needs to be removed ii) the lower shaft needs to be removed so the hook saddle can removed iii) the hook saddle will need to be machine milled out to accept the larger hook iv) the bobbin case opener needs to be changed v) the take-up lever has also has to be changed so the head assembly needs to be striped. vi) then the sewing machine needs to be reassembled and re-timed. vii) since the machine is basically striped to the bare bones you probably should repair the timining belt The real question is the conversion really worth it on an older machine? Doing it you self, if you can mill the hook saddle, for probably $150 US or so. Getting a sewing machine repair shop to do the work you are probably looking at $600- 800 US. So is it really worth $750 to $950 to upgrade the machine? I would suggest either: i) leave the machine as is and put up with the more often bobbin changes. ii) sell the machine and purchase a machine with the larger bobbin like the Consew 226RB-5. A new complete setup machine , table and servo motor would cost about $1500. t If you are going to get someone to do the work for you what are you willing to pay . kgg

Here is two manuals which may help. kgg 45k53.pdf 45Kmanual-2.pdf

Here are two manuals which may be of some help. kgg Pfaff_141,_143,_145,_151,_153;_142,_144,_146_Instruction_Manual.pdf pfaff_145-manual-EN.PDF

A good place to start for info would be the "A1 Repairing or the "Shoe Makers Friend" at http://www.sewmuse.co.uk/bradbury/a1 repairing.htm Parts maybe as scarce as hens teeth particularly with the machine not being produced for the last 100 years. The closest copy of the machine I can think of would be the Chinese Shoe Patcher fondly known as the "Tinkers Delight". I would love to see some photo's of your machine. kgg

Very nice setup for the right handed user. kgg

How how thick and rough is the surface of the polyester webbing. I ran across this problem when I tried to use a thick very knobby webbing. The basting (double sided) tape needs surface contact so the smoother the two surfaces you are trying to connect the better particularly with smaller widths of basting tape. You could try regular heavy duty double sided tape or gluing the webbing in place but the downside maybe those may gum up the needle. A photo of the webbing may help with what's going on. kgg

The Oren appears to be similar to the Yamata fy810 so you could try and contact them at Yamata USA Inc now called Ricoma at ricoma.com. A temporary alternative would be to install a cotter pin or a nail of the same diameter if there is enough clearance. kgg

Looks in great shape and a right handed machine to boot, very unusual these days. kgg

The needle is striking the feed dog so the position of the feed dog needs to be adjusted so readjust both the Longitudinal and Lateral position. This may have occurred if the height of the feed dog was set to high above the needle plate and the inner presser foot slammed it out of position. kgg.

Maybe you might what to ask in another post what the clone of the PFAFF 191 is. kgg

Which province are you in? Expect the prices for the PFAFF parts to be expensive if they can be had. The main contacts for PFAFF Industrial: Canada: PFAFF Industrial Canada Inc 5.03 Google reviews Industrial equipment supplier in Montreal, Quebec Address: 4949 Boulevard Métropolitain E, Saint-Leonard, Quebec H1R 1Z6 Phone: (514) 389-7836 All of North America: DAP America, Inc. PFAFF Industrial Division 5875 Peachtree Ind. Blvd. Suite 220 Norcross, GA 30092-3677 Phone: 770 446 8162 Fax: 770 446 7521 ricardodossantos@dapamerica.com http://www.dapamerica.com/ kgg

As @Wizcrafts said the needle plate has a square slotted cutout to allow the movement of the feed dog from front to back. The Cobra Class 26 is basically a clone of the Juki LS-341 / LS-1341 and has a hole in the in the feed dog with the standard inner presser foot also having a hole. The needle should always go through the center of the hole in the inner presser foot and move front to back in unison. Also the needle will go through the center of the hole in the feed dog and also move in unison with the the needle. A couple of things to check: i) Longitudinal position of the feed dog (page 2 of manual) ii) Lateral position of the feed dog (page 3 of manual) iii) Needle-to-hook timing (page 6 of manual) iv) Feed cam timing and Feed motion (page 12 to 16) I have attached the Service Manual for the Juki I am referencing. kgg Juki LS-1340&42 Servcie Manual.pdf

I find Schmetz needles work the best in my machines. Buy a brand name like A&E and stay away from the cheap Chinese stuff particularly the 8 oz spools. Buying a brand name thread will save you a lot of frustration. I use A&E (www.amefird.com) thread in either bonded polyester or bonded nylon. I think this is just to thin of leather to allow proper seams appearance for a Class 441 machine. If this is the thickness you are going to typically sew I would suggest getting the narrow feed dog and needle plate that @RockyAussie came up with and also refer to @Wizcrafts article on dumbing down a Class 441 machine ( Dumbing down a Cowboy CB4500, Cobra Class 4, or similar harness stitcher ( https://www.rw-leatherworks.com/blog/2019/02/dumbing-down-a-cowboy-cb4500-cobra-class-4-or-similar-harness-stitcher.html )). No, for V207 thread which is Tex 210 the needle should be a #24 and in thick / tough / sticky materials you may have to go up to a #25 needle. The #23 needle is for V138 (Tex 135). kgg

I looked at your video's and here are my comments: 1.) Your top thread should come directly from the top guide above your thread spool to the second hole in the vertical guide and wrap backwards coming out the fourth hole to the top tensioner. 2.) Your thread at the head appears to be correct. 3.) The shuttle plate appears to be dry and needs a drop of oil inside. 4.) The feed dogs appears to have rust which may indicate other rusted parts which maybe rubbing and cleanup. 5.) When removing an item from under the needle pull out a few inches of top thread first so you are not causing strain on the needle and possibly cause a bucket in the needle. I would recommend removing the hook to inspect it and the surrounding area as there maybe a burr, needle may have struck the hook at some point, the tip of the hook maybe worn or filed back and need replacement. I would recheck and re-time like they do with the Cobra Class 4. A couple of photo's of the hook maybe helpful. kgg

If your timing is correct and the machine is timed properly I would figure your dealing with a tension problem. Since you removed the bobbin assembly to clear a tangle I am going to assume the problem lies with the bobbin tension. When you removed the bobbin shuttle plate you may have screwed the two screws in tight, which would be incorrect. Screw them in fairly snug and back off about, I think, a 1/4 - 1/2 turn. Since this is a used machine another bobbin problem could be the actual bobbin tensioner spring has at some point been over tighten (will decrease the tension on the thread as it will cause the tensioner to bend away from the bobbin body), has been bent outward by incorrect bobbin threading, the bobbin has been installed incorrectly and the spring in the bobbin case has been damaged. Even through the following video's are for the Cobra Class 4, which is basically the same machine, it will provide better instructions on installing, threading and tensioning the bobbin thread. kgg

The second photo in the ad @Wizcrafts referenced will give you the dimensions of the bobbins so you can compare. kgg