Constabulary

to me the tip on the installed hook (shown in video) does not look bad at all. I doubt you have to replace it. It´s juts not correctly timed.

I have to admit binder are a special topic but the cheap ones are not against you. It´s just tinkering and knowing how to set up the binder. I´m using the freakin cheapest binders I could find (back then) and they work very well. Mine came from kits for flat bed machines like these (just minor differences): https://www.ebay.com/itm/353465220561 and I modified the brackets to fit my 108w20 cylinder bed machine. Zero issues - really! You can find complete 111w binder kits like this one: https://www.ebay.com/itm/300921860528 Pretty sure College Sewing has all the components.

You are welcome. I`m using Singer machines only and that for a reason - or several reasons. But each to his own - others love Pfaff for their own good reasons.

Let he check I may have one. If not check this post here

just wanted to post a link Yeah, thats the needle plate + feed dog combination one I´m using. The thread guide on the needle bar came with the needle bar. The NB came from a German made Singer 111D and has a wire type thread guide mounted on the backside of the needle bar. Is your missing?

The instruction manual is pretty clear with the timing values - SARK9 posted an extract above. If you do not have the complete manual download it.

Indeed - well done

Thats the point! Just as everything in sewing - it has to be set up properly... needle bars, hooks, feed dogs, feet... you name it... edge guide, binder brackets and attachments. And sometimes it requires to modify parts cause not everything comes of the shelf and is a universal fit part. There are just toooooo many variables in sewing. @chrisash the swing bracket may be a solution but is not guaranteed to be the solution that works "of the shelf" For the 111 there are special raised throat plates + feed dogs for binders, built up slide plates (for drilling holes and taping thread) and feet sets for binding... just dig through their 111 parts side (also look at the Singer 211 and Juki 562 / 563, Seiko STW 8 / LSW part sites)

Don´t look up the full number, everything after 442 is the subclass that describes technical feature which may or may not come with the machine (machine could be technically altered). Here are some files for the 442: https://www.manualslib.com/manual/1226488/Pfaff-441-O.html#manual https://usermanual.wiki/ACE-EASTMAN-PDF/Pfaff442144272004.1282822958 If it was me I would look for a Singer based double needle machine (like Seiko, Consew, Mitsubishi, Juki, Singer of course) because parts and accessories like feet and gauge sets (for different needle spaces) are a lot easier to find and a lot cheaper. I have a Singer 212G141 needle feed machine and I´m pleased with it

if not the safety clutch then IMO the NB is too high AND the hook is too far away from the needle scarf.

What diameter is the pulley on the servo? A small pulley will help too. The lowest setting on my JACK Servo is 500 but it actually starts at 200 and I have a 1:3 reducer + 40mm motor pulley. That lets my Singer 111G156 sew super slow

you could add a speed reducer. https://www.google.com/search?client=firefox-b-d&q=speed+reducer+site:leatherworker.net/forum/

Binder is too far away from the needle, bring it closer to the needle and if necessary cut down the inner foot.

For spacing between the needles. The bars seem to be fixed in space but the different needle holders (one for each NB) are available for different needle spaces. Split needle bar machines are a bit different compared with plain double needle machines.

loosen this screw and you can raise or lower the feed dog. Removing the front plate (held by 4 screws) makes it a bit easier. Yes, that´s the only mechanism. Have you checked the stitch length adjuster? Lever up is short lever down is longer. If the lever does not move then loosen the set screw on the front side

The days of OEM Singer parts are over (almost) and no one will offer the complete set I guess. So you most likely have to buy the single parts and assemble them. Also make sure your cam on the top shaft has the bevel gear mounted.

Often the main problem is a seized needle bar. I would loosen the the 2 clamping screws on the NB clamp and apply heat (maybe with gas blowtorch) on the bushings and oil them and try to free the NB with a piece of wood and gentle hammer strikes. Heat and oil will most likely loosen the top shaft too if it is seized. this was my ".45" project - pretty much the same machine :

I´d go with #3. Though I like the Durkopps very much cause they share a lot of parts with Singer 111 machines so presser feet sets are available fairly cheap.

Maybe the parts list of the Consew 255 or similar machines like Singer 211 / 212 give you an idea. If not helpful just oil the machine manually. I have a Singer 212 and so do I.

manual can be found here. https://manualzz.com/download/29222852 Parts list: https://www.manualslib.com/manual/483282/Brother-Lt2-B835.html looks like a machine with switchable needle bars. I do not know if it is possible to adjust the needle bar space. Other than that I´m sure the machine is using the the standard gauge sets as used for Singer 212 needle feed machines as well as for their Seiko, JUKI, Consew... equivalents. EDIT: looks like there are special gauge sets for this machine available. Apperas needle holder are different: https://www.ebay.com/itm/1SET-AUTO-THREAD-TRIMMER-GAUGE-SET-FIT-FOR-BROTHER-LT2-B835-LT2-B845-/163232435756

Please post pictures of your machine. There were 2 Types of 51w machines and early and and a later model. Maybe this helps a little bit:

The World was waiting for someone like you

175 yrs of sewing machines and they are still inventing new needles... I had to look up MR needles. See attachment. It may solve some issues but a properly set up machine and the right needle size is still mandatory. The_special_application_needle_MR.pdf

it may depend on the thread sock and how tight it is on the cone but I leave it on (the fine white ones) - no issues and no need for adjusting tension so far.

Posting pictures will help to figure your problem. Needle clamp screw should be parts number 201030 and should be available from a sewing machine dealers. But better check the parts list of your machine. Check the needle hook timing when the hook is not catching the thread. Most likely needle bar is a tiny bit too high.