kgg

To be 100 percent sure about the specs I would check with @CowboyBob he would know for sure and probably has a manual kicking around. kgg

Same as normal sewing machine oil like Lily White. kgg

The manual actually says 16.0 mm2/ sec. which is equal to 5W oil. kgg

Most people use regular sewing machine oil. Normally you would follow the manufacturers recommendation as outlined in the manual. Most people I think use a Lilly white sewing oil or a variant. Lilly white has a viscosity of 5W. As a note a higher viscosity will make the bearings carry the load better at lower speed, but maybe not great at prolonged higher speeds. I personally never use normal sewing machine oil in any of my machines old or new but that is my choice. I use a blend of synthetic motor and synthetic transmission oils. If the machine is old I will use a higher concentration of transmission oil to flush debris or dried oil out so the bearings can get fresh oil in there for lubrication. If there is minor wear in the bearings I use a higher concentration of motor oil. If I am doing regular oiling I use about 20 percent synthetic transmission oil in the blend. I find the synethic oil blend makes the machine run smoother and quieter. Just in case you don't have a manual for your machine I have included a pdf. Refer to page 4 "Oiling" for what the manufacturer recommends as far as oil and oiling interval. The problem of staining I find is caused by over oiling. kgg 1245 Owners Old Case.pdf

This machine from what I understand is: i) A drop feed needle feed machine. Not what I would attempt to use for holsters as you really need a compound sewing machine (feed dog, presser foot and needle) for leather work. ii) I would consider this more geared towards fabric then leather. iii) As far as sewing 1/2" I think this is very doubtful, at best maybe 3/8". iv) The thread limit I would suspect would be V92 maybe V138. How thick is the leather you are planning on sewing? What size of thread are you wanting to use? Are you sewing presently by hand or by machine??? The first I have ever heard of the shank size determining the sewing thickness. kgg

Sorry, early morning Nicotine level was low. Hadn't had my second cup of coffee and enough vaping. Use to be second cup of coffee and six smokes. kgg 341 engineer manual.pdf

Here is a copy of the Juki LS-431 engineering manual refer to section 9 page 12. kgg

If I'm not mistaken the fabric needles would be DDx1 which are 214x1 needles. I still would check with a Seiko dealer or your manual. kgg

I would say those made in Switzerland then either those made in Japan or Germany. The problem is getting screwdrivers that seat and fit properly as well as being durable so sometimes you need to go with metric sized screwdrivers to get a better fit to avoid screw head slop. kgg

The green arrow points to what looks like a oiling port for the internal parts similar to the Juki LU-562 & 563. The red arrow points to the stitch length adjuster as I don't see a stitch length adjusting dial or it is a safety clutch to protect the hook assembly when you jam up the machine. If you want to wind just a bobbin: Here is a link to pretty good video from the 9:00 minute mark ( i) remove thread from needle otherwise you will jam the machine up. ii) the winder needs to be set so it trips out when you get about 80 percent of the bobbin filled. iii) install empty bobbin on winder shaft. Most bobbins have holes on the sides of the bobbin so a) the end of the thread from the spool of thread you are using to fill the bobbin through the winders tension discs then to the inside of the bobbin outwards through a hole b) push the bobbin trip lever towards the rear of the machine to engage the winders drive wheel up against the machines drive belt c) hold the end of the thread in your hand d) hit the go pedal e) hold the end of the thread until you have at least two complete rows wound on the bobbin. iv) you really should have two spools of thread one for the top thread and one for the bobbin thread so you don't have to unthread the machine just to wind a bobbin. kgg

Industrial flatbed upholstery machines similar to the Juki dnu-1541 S and similar clones will typically sew 3/8" (9.5mm) while the cylinder arm machines similar to the Juki LS-341 or 1341 and clones will typically sew 7/16" (11mm). Once you go above that thickness and / or higher then V138 thread you need a a Class 441 machine, which the one armed bandits are, either manual or motorized. When I wanted a class 441 machine I choose to go with a motorized machine as for me I figured the bloom would quickly fade having to move that lever up and down for each stitch. The class 441 machines excel at thick / tough leather but can be dumbed down to thin stuff with smaller thread. I suggest you follow the 90 percent rule, doing mostly thinner flat items get a flatbed or a cylinder arm machine with a table top attachment. No one machine will do everything. Buy Once, Cry Once Here is a great article you should read to help figure out what machine would be needed for your stuff. kgg

There are three one armed bandits that have similar capabilities. i) Tippmann Boss costing about $1000 USD ( https://tippmannindustrial.com/tippmann-boss-leather-sewing-machine/ ) ii) Cowboy Outlaw costing about $1600 USD ( https://www.tolindsewmach.com/cowboy-outlaw.html ) iii) Weaver Master Tool Cub costing about $2100 USD ( https://www.weaverleathersupply.com/products/master-tool-cub-manual-leather-sewing-machine-aluminum ) Some people prefer one over another but either should do the job. The thing to remember is the that all three are made to sew thick leather with a thick thread up to V415 and use a needle that is about the same size as a 2 1/2" finishing nail. The main question is what you want to sew and from there choose a machine. kgg

To further what @Constabulary said here is a line from ISAC.net about the Singer 17-2 ( https://ismacs.net/singer_sewing_machine_company/singer-class-17-sewing-machines.html ) " Machine No. 17-2 has drop-feed across arm at right of needle and is used for closing the seams of Shot or other bags after they are filled, sewing buckram on Jean Pants, Pocketbook manufacture, etc. " Personally I think you should be looking for machines similar to at least a Juki LS-341 or clone depending on the thread size / toughness of the leather (chrome tan or veg tan). With old machines when you get into the 75 year bracket whether they are brand name or clone finding replacement parts can be expensive or sometimes impossible to find. If you can't find parts you wind up with a pretty boat anchor. When setup properly it is a game changer as you get the presser foot, the needle and the feed dog moving your item along particularity on thick items or multi layers. kgg

Basically you saved about $1200 USD or more for a similar machine being sold in the US. kgg

Looks good. You really should flush the machine prior to doing any real sewing to get any bits of manufacturing stuff out of the machine. Oil everything just not what is suggested. If it is metal touching metal oil it. Two questions: 1) Is that a plastic pulley on the servo motor?? 2) Cost Here is a couple of pdf's for the Juki LS-341 that may help. kgg 341 engineer manual.pdf Juki LS-1340&42 Servcie Manual.pdf Juki_LS-341N_Engineers_Manual.pdf Juki_LS-341N_Instruction_Manual.pdf