Constabulary

Hope you are aware of import taxes and VAT.

Long wait - so I guess you bought it on Alibaba and have it shipped to the UK?

The orientation of that thread guide should not be an issue. Anyway, it is held in place by a tiny set screw coming from the top. See picture (yellow circle). Top thread look correctly threaded to me. So what is going on with the bottom thread. Or what is the overall problem? is it not sewing or not picking up the bottom thread?

Be careful when taking it apart - parts are no longer available for this machine!!!! There is nothing Singer or Adler compatible on this machine. Looks like 1 or 2 plain springs are missing. Also leave the top shaft in place. Do not remove it except you know how to safely remove the cams and how to put them back on w/o damaging. Also be careful with the heart shaped cam on the needle bar. It is attached with a pin. Well, your decision but be careful! Lets hope your machine has the shuttle hook and bobbin cause they are no longer made. This was my class 17 restoration but mine was an earlier type.

Please post some good clear pictures of your machine

What needle size are you using? I would guess you need a needle 1 size bigger (for a larger hole) or more top tension or less bottom tension

Maybe it is not threaded correctly. I unfortunately cannot give you any timing instructions. I rebuild a Class 18 approx 5 years ago and sold the machine later. That was the only class 18 I ever have worked with. I never touched one again. The Class 18 hook system is very unique and not comparable with "elastic" hooks as you find them in common patcher machines. This was my restoration journey (making 1 out of 2) back then maybe you find something that helps you. On page 2 I posted a video showing how to thread the machine all the moving parts and the cycle of how the hook system works / the hook it catching the thread loop . Hope this helps.

There are 2 basic types of 51w sewing machines, an early type with thread take up lever on the left side and the later type with thread take up lever on the front side. You can download the manual for either type here. They should help to figure which one you have.

Looks like an H4 machine, that means it should have 14mm foot lift!!! Before you let this machine go better test it to see if it suits your needs. Not having a drop feed does not mean that it only can do binding work. Pfaff 335 and Adler 69 also no not have drop feed (some do but most don´t) and they are very common in leather work. Back in the old days there were leather sewing machines with only needle feed meaning they had no feed dog at all and they worked! So if I was you I would test it before I make a decision only by the digits on a brass plate. Keep in mind that these digits just show how the machine was set up when it left the factory but it does not tell you if the machine has been modified. Test it - then make a decision. My 2 cents.

Yea the 211 are a pain when it comes to hand wheels. I failed to remove it on my 212 (same as 211 but double needle). The 111´s are easier to work with IMO. But you can add a speed reducer instead of installing a lager hand wheel if you want to slow down the machine. Anyway - If I had to choose between the 2 above machines I would go with the 211. Are you sure the 230 is a walking foot machine? To me it looks like a plain drop feed machine.

maybe you should tell us what thickness (all layers in total) you want to sew or what product. The 236 have a rather short stitch length and are meant for sewing shoe uppers and the like.

looks like a 29K70 or 71 or the like but W/O front wheel or is and an earlier model in the K60´s subclass?

Seems several parts are missing and machine has no reverse. Table top is bad and motor for sure is an old clutch motor. Not what I would buy.

I don´t think you can get the OEM wheels anymore (well maybe... you never know). If I were you I would probably take a wheel from a different bobbin winder then wrap a piece of leather or PU flat belt around it and adapt it to the spindle. Spindle is present I guess? Other than that I would buy a table mount bobbin winder https://www.ebay.com/itm/143422223667 But it may need some modification as well.

30-10 is the newer version of the 30-1. Technically there is no big difference. Both are small bobbin patcher machines with the same stitch length and foot lift. Spare parts are expensive.

not all new machines are necessarily clones of "old / big name" manufacturers.

Or the needle size is too small so the needle hole is not big enough for the bottom an top thread and the thread knot cannot be pulled into the material. Try a bigger needle or smaller size the bottom thread.

Thats right. The original question was for a 111w.

PE means Polyester I`d say and 35 could be thread size TEX 35

Maybe the discs with the stitch length numbers has slipped. I´m not in front of your machine so I only can guess. I would try this. Open the cover plate on the top. Loosen the set screw of the stitch length dial. Push the button in the flatbed and turn the hand wheel towards you until you feel resistance. Then the longest stitch length dialed in. Then rotate the stitch length dial until you see the 5 in the window in the casting and tighten the set screw again.

@kidbeey I just recalled this thread here. Maybe this is interesting for you. Contact him by sending a PM cause he only made 2 post here.

check what diameter the bobbins have that come with the machine, small ones are approx 16.5mm the large ones are approx 20mm in diameter.

Your stitch length adjuster is installed upside down. The arrow has to point upward. Also make sure the gib is instilled correctly.

BTW - hope you are aware that is is not a heavy duty leather sewing machine. It was used for sewing garments and maybe some lightweight leather. What leather thickness (all layers together) do you want to sew and with what thread size? Those who think it is a heavy duty machine usually come form domestic sewing machines and think because of size and weight it has to be a "Hevay Duty" machine.

There were pre wound bobbins for barrel hook machines? Can you post some pictures please? Did the machine come without bobbin winder? That surprises me. This one should work: https://www.ebay.com/itm/143422221569