kgg

Your machine should be able to handle up to V138 thread. Here is a good needle to thread chart: https://www.tolindsewmach.com/thread-chart.html Here is a link to a video that shows a visual comparison of thread. A couple of notes about the linked video: ( http://www.youtube.com/watch?v=-lfMD8WEHoE ) i) the person doing the video really doesn't understand the various thread sizing / labeling of thread. ii) The white threads he calls it a #40 is V69. By looking at the label it appears to be a Chinese thread and they typically size their thread in the metric sizing and a #40 is the same as V69. iii) The burgundy thread he calls it a #92 which is V92 and appears correct. iv) The purple thread he calls it a #135 which appears to be a Tex 135 and that is the same as V138. v) The red thread he calls it a #138 meaning V138. That is the US standard for thread sizing. The purple and red thread are the same just a different way of indicating it's size on the label. From what I have seen is the Chinese threads are usually just labeled in the metric size with a "#" while North American threads are label with both the "Tex # XXX" and the US standard "V # XXX". Do yourself a favor and buy good quality thread not the cheap Chinese stuff and get better results with less frustration. Thread size V69 ( Tex 70, 40 M, 40, Tkt 40 ) is the largest size most domestic machines can handle and is the crossover size to industrial sewing thread. Confused yet? kgg

The correct needle system for the Singer 111W156 is 135 x 16 for leather and 135 x 17 for fabric. The person might have owned a PFAFF machine or purchased them incorrectly or converted the machine to use needle system 134. I would pull the needle in the machine and see what is actually in the needle bar. Like @Constabulary check the needle bar height and use needle system 135 x16 or 135 x 17. kgg

With a max 100 (#16) needle you are going to be very limited in your thread size (V69 max) which in turn is going to limit sewing thickness ability. From that needle size. From that spec alone I would not recommend purchasing this machine for what you originally listed as items you want / need to sew. kgg

According to the spec ( https://jukiquilting.com/media/catalog/product/t/l/tl-18qvp_instruction_manual.pdf ) on page #4 your machine is only rated for V46 (Tex 45) max as it on that a domestic needle up to a #14. That did surprise me. Most domestic sewing machines can handle V69. If I'm not mistake that is usually a spec for quilting machines. In my opinion V69 thread is the cross over point from domestic to industrial machines. Here is a good needle size to thread size: ( https://www.tolindsewmach.com/thread-chart.html ) which also gives the strength of the thread. In most cases as the thickness increases it is easier to bury the thread knot with the right machine. I do really like Juki machines but you can get a comparable clone for a lot less which may serve you really well. If you go the clone route ask the vendor what it is a clone of from that you can determine pretty quickly what it's capabilities are. Still unsure just post a question to the form before you buy, I'm sure someone will be able to help. kgg

Those machines are basically clones of the older Juki LS-341. Getting a cylinder arm with a table top attachment and there are many available would be a good all rounder. It will give sorta kinda give you the ability of a flatbed machine. Remember there is no one machine that will do everything well. My experience is that some industrial machines even though rated for V69 ( Tex70 ) really don't like it and can be really finicky with thin thread in thinner items, preferring V138 (Tex135). What you may find is using your Juki TL-18qvp for the linings and the cylinder arm for the leather portion of your project. Most upholstery class machines like the Juki DNU-1541S are rated typically to handle up to 3/8" of leather while the cylinder arm machines like a Juki LS-341 can handle up to about 1/2" or so of leather. The main problem with using 2 oz leather is going to be setting up the machine, cylinder or flatbed. Getting the knot to be buried in the leather. My Juki DNU- 1541S hates working with thin stuff that is why I have a Juki DU1181N rated for V92 but I run V138 in that machine with no problems. If you decide to go with a flatbed I would suggest going with the Juki DNU-1541S. I have owned both the Consew 206RB-5 and the Juki DNU-1541S. In my opinion the Juki is a much better machine. Since this is going to be expensive no matter which machine you decide on I would suggest going to a vendor with a sample of your stuff and test drive some machines. Buy Once, Cry Once kgg

I have a little Juki 1181N that has an oil pump but like @dikman I do manually oil the machine. The problem with a lot of machines that have an oil pump is we don't run them flat out and at slow speed the pump probably does provide proper lubrication. To combat that when I need to use that machine I always first remove the thread from the needle lift the presser foot up and run the machine for a couple of minutes at a slow speed then gradually increasing the speed to a fairly high rpm. kgg

Depending on what you are sewing you may need different feet like left toe, right toe, piping, etc. and if you are doing binding you need binders/folders, etc. The roller guide you may find gets in the way a would prefer a drop down guide with a straight edge rather then a roller guide. The list is endless it just depends on what will make you projects go easier. Finding some accessory items for PFAFF can be a chore, if available, particularly for older machines. What is the max needle size in system 134 that this machine is rated for? If it similar to the 335 going above V92 (30 M) then this could be a problem. What size of thread do you want to use?? What is the max thickness you want / need to sew??? kgg

I think to get both sides properly done and that can be consistently repeated you need to start out with a good mold. A mold that consists of two halves where the bottom half and top half can be compressed together otherwise you will never get proper fitting item. You could make a mold out of wood or have one 3D printed. I suspect a 3D printed mold would be the best cheapest route. kgg

With odd ball setups like this one I totally agree with @Constabulary. When those bells and whistles work they work very nicely and do good work but when they don't it would probably be cheaper to junk the machine rather then trying to repair them. I would suggest you try and find a machine, flatbed or cylinder arm, that has a standard setup say comparable to a Juki DNU-1541S (flatbed), Juki LS-341 or 1341 (cylinder arm ) or clones. The parts and accessories are a lot cheaper and can be readily had should something happen. kgg

Also you need to add the weight of the packing particularly if the unit is used and it is being shipped by wooden crate. Also ask the seller to send a photo of how they are planning on packing it. If it is not properly packed up you could windup with a box full of broken parts. Also have it insured against shipping damages. kgg

To get controllable slow speed sewing and to reduce your frustration level I would suggest: 1) dump that clutch motor ---- Clutch motor: i) It is always going to be on at full speed probably revving at 1750 rpm's or 3500 rpms. ii) It is going to be annoying loud. iii) Learning how to feather the clutch has a very steep learning curve for most. 2) Install a servo motor: i) about $150 this side of the pond. ii) More energy efficient as the motor runs only when you press the "go" pedal iii) More bottom end torque. iv) ability to set the speed and no matter how hard you depress the "go" pedal the speed will not exceed that setting 3) install a speed reducer for added torque but most importantly added speed reduction. kgg

No, you well screw the machine up and have a terrible mess on your hands. You will have to: i) have the needle in the down position and just on it's way up so the hook has caught the bobbin thread ii) raise the presser foot just off the material and slowly turn the item around iii) drop the presser foot down and sew Chances are you will not be able to use V207 thread consistently in thick or tough materials or materials with pile layer like carpet. I would recommend V138 with system 135 X 16 (leather point needle) using either a size 23 or 24 needle. Are planning on doing a single fold or double fold with the leather binding and how thick is the leather binding??? kgg

Before getting your next machine you should post a new topic that your are considering XXXX machines to do your particular work. You will get the good, bad and ugly about the machine before you buy it. kgg

That is a very pretty table but seems impractical to me with limited usability for a cylinder arm machine more of a show piece. The drop leave end is nice space saving touch. I think when you are sat at the machine you will find that you are going to have to put one leg outside the left side table leg which probably is not going to be a comfortable sitting / sewing position. Also that beautiful hardwood swivel is going to be real pain in the butt, literally. The question I think is would this table arrangement work for the items you want to sew? If you plan on doing bag type work a cylinder arm mounted on a flat table like this one will not give the freedom as a "U" shaped or a table that mounts the machine so the cylinder arm overhangs the end of the table which gives clearance basically to the floor. From the photo of the motor it appears to have the standard triangle mounting arrangement as all motors, clutch or servo. A servo will give you better speed control that is much more quiet then a clutch, cheaper to operator as the motor only runs when you press the "go" pedal and provide better bottom end torque. I would suggest finding either a brushed servo motor or brushless servo motor. Like @canvassewing has suggest a 750 watt would probably work quite nicely. If you choose a brushless servo motor the more internal coils it has the better the motor. A couple of questions: i) What do you want to sew?? Fabric, Leather ii) What size of thread do want to use?? iii) Which model is this PFAFF machine?? iv) What are they asking for it?? You maybe better off buying a clone with a proper industrial table setup. kgg

I agree with @dikman this is a binding machine. I did look at the spec part of your "Made in China" advertisement: 1) particularly the "Presser Foot Lift" at 15mm. Allowing for a necessary 3mm (1/8") gap from the presser foot to the top of an item being sewn leaves 12mm as a very max sewing thickness, not necessarily leather. Your 12 oz of leather would have a total 4.78 mm ( https://www.weaverleathersupply.com/pages/leather-thickness ) so you would be well within having enough space under the presser foot. 2) the video on the "Made in China" advertisement. Shows this machine as what appears to be needle feed machine not a compound or walking foot machine made for Fabric applications. 3) The only reference I could find about the needle system was it takes system DP 17. The DP17 is the same as needle system as 135 x 16 for leather and 135 x 17 for fabric. I could not find any reference to the max needle size but looking at a PFAFF 335 manual it max out at a #16 (100 metric) which means it can handle V69 thread. 4) Here is a good reference chart for needle to thread size ( https://www.tolindsewmach.com/thread-chart.html ) My personal opinion is that this machine is meant to do "Fabric" work of flat binding with no major thickness changes like going from 1.6 mm to 3.2 mm (4 to 8 oz leather) using a max thread size of V69. The machine probably could handle V92 in certain types of materials. Just because you can stuff a # 22 or 23 needle in the needle bar that can take V138 doesn't mean it will have the necessary needle to hook clearance. I think this is the wrong machine for sewing leather of that thickness. To do the job properly and consistently with V138 thread in 12 oz of leather you need in a cylinder arm a Class 341 or 1341 machine like a Juki LS-341 or 1341 or clone. kgg