Uwe

Some parts are easier to make than to buy, especially for orphaned vintage machines. That thread guide is essentially a paper clip combined with some quality time with a pair of needle nose pliers. If you want to get fancy, get a thin stainless steel welding rod at you local welding supply store instead of a paper clip. The screw that goes with it is harder make and find. Hope it is a metric or common sewing machine screw, otherwise you may be, well, out of luck.

Part numbers often work best when looking for replacement parts. Check the Nakajima TDU-N62 parts manual for the part numbers. Then you can contact Superior Sewing to see if they have the part, google the part numbers or try eBay for research. Available parts sources vary greatly depending on where on this planet you are located.

Yup, looks like a chain stitch machine to me. Perhaps a Pfaff 5483? https://www.manualslib.com/products/Pfaff-5483-3645237.html

How much movement the feed dog and needle bar rocker frame make when using the reverse lever depends your stitch length and also on their starting position when you use the reverse lever. If your Juki LS-341 didn't move when pressing down on the reverse lever, it's because you either had stitch length "0" selected, or the feed mechanism happened to be perfectly centered front-to-back by chance (e.g. needle at the very top, or needle at the very bottom.) Select maximum stitch length and turn the hand wheel until the feed dog is at the very front, then use the reverse lever. That's when the reverse movement is most pronounced. Your Juki LS-341 works exactly the same way.

Did't I answer this very same question in one of your other topics?

Yes, moving the reverse lever will move the feed dog and needle bar rocker frame. When the feed dog is at the very front, actuating the reverse lever should move it all the way back. This is true for all "normal" sewing machines, not just the Pfaff 145.

Here's a 1/4" gauge set on Ebay:

Make sure you don't change the height of the needle bar as you rotate it and that you're not creating a new interference elsewhere (e.g. needle screw towards the back.) It's tight quarters and every millimeter counts. Also re-align the needle itself again to make the needle's scarf point to the right.

It looks to me like you could rotate the needle bar a little more to move the thread guide hole closer to the 7 o'clock position and still have access to the needle clamp screw, too. I know that several people have made this Q-feet work on Adler 67 machines without requiring modification of the foot. Sometimes these interference issues crop up when the machine is timed using a shorter needle than the specs call for. Double check your needle system.

Changing gauges is a non-trivial affair on a flatbed machine and usually also requires a matching needle bar. You also have to move both hook saddles - that's the part may be next to impossible on a post-bed machine.

You may simply need to rotate your needle bar a little so that the part that sticks out no longer touches the presser foot. That Q-design is taller on the left side than other feet. A picture of your needle bar near the presser foot would help. In general, don't run new accessories under power until you are certain that there is no interference.

There are a whole bunch of parts that move when you actuate the reverse lever. A tight/dry spot could be anywhere. The feed dog and needle bar rocker are all supposed to move when you flip the reverse lever. If the feed dog and needle bar rocker are all the way up front, they move all the way back when switching to reverse. That's actually a good way to observe all the parts that move and need some lubrication. There's also a block behind the reverse lever that slides back and forth on a rod. Make sure that mechanism is well lubricated. In general, keep looking/cleaning/oiling.

Sounds like you made great progress in your machine adjustments! The mechanical knee lift works as intended/designed. The mechanical knee-operated foot lift is not supposed to lock in the up position. Some electrical knee-switch operated controllers (e.g. Efka) allow you to set the knee-operated foot lift action using two different modes. One mode is to momentarily lift the feet only for as long as switch is actively depressed. The other mode is a toggle switch, where you click the knee switch to raise the feet, then you click the switch a second time to lower the feet again. This usually requires an air cylinder or solenoid operated foot lift mechanism.

Your stitch selector does work, and likely as well as you can hope for. They're not intended to be mathematically accurate, they're more of a rough guide. Actual stitch length varies with material type and thickness and sometimes even sewing speed. The simple fix is a little cheat sheet that tells you which number corresponds to which actual stitch length for a given material. Trying to make that dial accurate for all possible material combinations will be an exercise in futility.

On the far end of the spectrum is this super heavy duty Singer top+bottom feed zig zag machine. I'm not sure which model this is. I keep it on a dedicated hydraulic lift cart for a reason.

Here's the sewing demo video with my Pfaff 138 sewing oil tan leather patches onto canvas material. Hopefully it will give you some idea of how this machine handles that particular task.

The Pfaff 138 is definitely a full scale industrial sewing machine, designed to sit in a table and run on a clutch or servo motor. Here are a few pictures of my machines for reference and size comparison between Pfaff 130 and Pfaff 130. If I find time I'll do some test runs with denim and leather.

I just made a video on the subject of walking foot adjustments for Pfaff 545. Perhaps it will help you resolve the issues with your machine as well:

Here's how my Pfaff 545 is adjusted to get proper walking foot movement:

Your feet don't walk because the front foot doesn't really make contact with and press against the feed dog - it simply goes in circles above the feed dog. The rear foot can only lift up if the front foot can press against something (feed dog or material.) If you put some 1/4" thick material under the feet, they will probably walk right now because the front foot can press against the material. As to why your front foot doesn't touch the feed dog, I can't tell from the information you provided.

Let us know when you find a cheap industrial walking foot zig zag machine without issues. I want one, too.

That depends on your bank. A Pfaff 130 is a very nice vintage zig-zag machine that will probably do what you have in mind. Pfaff 130 occasionally pop up on CraigsList and other places for $100-200. Other vintage options are Singer 143W and variations on that theme. New heavy duty industrial zigzag machjnes like the Consew 199RB are over $2K And then there's always Sailrite if you need to sew denim/leather on a sailboat (or at home.) They don't get much respect here on LW, but they are probably fine for your application.

The original post with more details:

This is a Singer stool we collectively fawned over some time ago:

Guess you need a thumb wheel controller then [sorry, way off topic, but I couldn't resist]