Uwe

Wow, nice work! It's clearly a labor of love and it shows.

The cheap and perfectly functional way to do it is with a little magnetic, battery powered laser guide attachment. I think I got mine at Harbor Freight for less than $15. These are also available on Ebay for $12.50 . I also installed a fixed laser guide with a wired power connection on my Pfaff 335 once (the white LED spot light is from IKEA) . You can do a similar thing on a Cowboy 4500. Available on Ebay for around $15.

I'm under the impression that all Cowboy machines enter the country through Ryan O. Neel of Neel's Saddlery in Ohio (sad looking website but big YouTube presence with Cowboy demos) If a particular dealer doesn't carry a certain Cowboy machine, Ryan should have access to all Cowboy machines and he sells them directly, too. I personally favour the Juki-LS 341 design over the Pfaff 335, mainly because of the vertical axis hook, comparatively huge bobbin, and descending feed dog. That slim 335 arm comes with a few compromises, I think. Each machine design has its own advantages and shortcomings, you just have to decide which ones are important to you.

I got my Consew 104 set up in a test stand and did some stitching earlier today. I made a demo video for somebody who's interested in buying the machine and wanted to see it work. I thought I might share the video here for general entertainment. The machine is quite a different animal from what I've worked on before. I really don't see how a lockstitch machine like a Singer 20U can produce a stitch like that. I also think this Consew 104 would be quite capable of putting embroidery designs like monograms and swirly designs on garment weight leather. I'll try that out on Sunday.

Check out this thread on Singer 29K60 info including threading. Make sure can pull the thread manually and that it's not caught anywhere.

A nice, thorough tutorial on that machine, with threading details and all.

Perhaps something in your tension release mechanism is stuck and keeps the tension discs apart. You should be able to feel a distinct difference in tension when you pull the thread manually and change the tension setting. If the thread tension doesn't change as you dial the tension knob, you have to figure out why.

Post a picture of how you have your machine threaded at the top. Are you sure your thread is even between the tension disks? Sometimes it takes a little effort to snap the thread between the disk, don't just loop it around them.

Are those watch straps machine stitched? Even if you manage to sew parts of the stitch line on a machine, some details will have to be done by hand. Most regular machines will have throat plates and feed dogs much too big for those tiny stitches that close to the edge. You may want to consider using a cylinder arm machine that has optional throat plates designed for "small operation". I think your watch straps qualify for small operation (with surgical precision.) I've not personally used the feet and throat plates shown below, but they seem like reasonable candidates to consider. The came from the Kwok Hing page for Pfaff 335 accessories. The 335 S3 Needle/Throat plate and the 335 S4 feed dog seems about the right size for those tiny stitches on your watch straps, and without leaving too much of a hole in the plate for things to get caught up in. For matching feet, it seems to me the KP335LB could be modified similar to what I did in the video (grind off areas inside dashed boxes) to sew extremely close to the edge and staying clear of the raised part of those straps. Alas, you won't know for sure until you try it out.

I first saw this concept on 441 style presser feet (photo from Toledo Bob's website):

Here's one approach that might work, using a modified outer presser foot and a suitable throat plate:

Technically yes, but it's not easy and involves a couple of other parts, not just the hook.

In defense of Consew servo motors, I recently put together a $110 Consew Premier CSM550 motor with a 50mm pulley and a 3:1 speed reducer to power my Consew 225. Below is a video of this combo sewing 6.2mm (15oz) veg tan leather using size 138 thread and a size 23 needle (I misspoke in the video). To me, this cheapest of servo motors plus a speed reducer (that cost more than the motor) leaves little to be desired in terms of consistent low speed control and punching power. I'd love to see somebody do this with a clutch motor.

I think you mean Cechaflo on Youtube. He's a master of the manual step backwards. It seems he only uses his machine's reverse lever when he doesn't care where the stitches go.

I had a similar problem when I was working on my Juki LU-563 clone. In that particular case the issue was resolved by shifting the timing belt by one notch. It seems your problem is similar, except the Pfaff does not have a timing belt to synchronize upper and lower drive shafts. Perhaps there are marks on the drive gears that need to be aligned. Here's how the machine worked after the timing belt adjustment (and re-timing the hook):

The reverse lever should not be bouncing up and down as you sew. It's often an indication that something involved in the feed mechanism is hitting a limit and something else compensates for it. I'd recommend spending some quality time with the Singer 211G Service Manual and comparing the suggested adjustments to your machine's. Sometimes a less-than-max stitch length is due to the feed dog starting to move backwards before the needle pierces the material (or starts to move forward before the needle exits the material.) Removing the material and turning the machine over by hand will allow you to see what's going on/wrong and make corrections.

If the thread is too tight wrapping around the bobbin case, your top-to-bottom drive shaft timing may be off. One quick way to check is that when the thread is wrapping around the farthest point of the bobbin (directly opposite the needle), the thread take-up lever needs to be at its bottom-most position. The thread should not snap around the bobbin case. Make sure when you make adjustments that you use the specs provided in the Pfaff 1445 Adjustment Manual. If enough things are just a little bit off, it may add up to a bunch of trouble. As for the occasional bird's nest underneath when you start sewing, it's probably because you're not holding both threads taught for the first few stitches.

A hook type blade in a utility knife might be worth a try: Or a safety carton cutter:

I made an adjustment video for the Juki 563 class a while ago. Your Juki 562 has a smaller bobbin, but is otherwise nearly identical. It may be a good starting point for your machine. My Consew 225 hook timing video is also a good starting point to understand what's going on.

I had one machine that did the same thing. Upon closer inspection the inner presser foot shifted very slightly to the left whenever it touched the feed dog. The sideways shifting was very obvious when turning the machine over by hand with no material under the feet. The cause turned out to be a combination of a worn feed dog (the top surface wasn't level but slightly sloping down towards the left) and too much sideways play in the upper swing block that moves both needle bar and inner presser foot bar back and forth. The swing block had sideways play because the guide plate was not close enough (or worn). Replacing the feed dog and tightening the guide plate clearance solved the issue in my case. A loose feed dog may also tilt slightly sideways when pressure is applied. The Techsew 2750/Juki 341 design has the upper swing block pivoting in the center and there's no guide plate like in the Juki 563 style heads, so the center pivot screw/bushing may be loose or worn and allowing sideways play. Checking for sideways play in either feed dog or inner presser foot/needle bar should be easy. Also check the feed dog for uneven or sideways sloping top surface (this may happen if grinding down the feed dog to blunt/remove teeth.)

Ah, yes, the sequence of sewing steps makes a BIG difference, too. If you've been sewing all the seams of your shoes on a domestic flatbed, then you'll obviously be fine using an industrial flatbed. Flatbeds usually cheaper than their cylinder arm counterparts. The Consew 205RB5 is really a made-in-China clone of the made-in-Japan original, the Seiko STH-8BLD-3. The Seiko's are great machines, really. You can buy a complete Seiko STH-8BLD-3 for around $1250 plus shipping (e.g. Westchester Sewing.) I also have a new Seiko STH-8BLD-3 for sale ($1,200 in a table with servo motor, plus shipping. Send me a PM for pictures and details.)

I'm not familiar with your Kenmore machine. Domestic machines often have a "free arm" which is similar to a cylinder arm. I'm not sure how you could sew the two stitch lines on the front of the shoes on a plain flatbed machine like the 206RB5. Much depends on the design of the shoes. There's another member here on LW who makes baby shoes, and she used a Durkopp Adler 867 flatbed machine for her shoe designs. I'll second Mike's recommendation for the thin cylinder arm (e.g. Pfaff 335, Adler 69, or similar) and definitely a servo motor.

Yes: Toledo Industrial Sewing Machines

I have a nice Consew 225 that's looking for a good home. In a used table with basic, new servo motor it'd be within your budget of $600. I'm about two hours away in the Detroit area, a bit of hike but doable. The machine is featured in several of my youtube videos (see link in signature below). You can send me a PM if you're interested.

Best way to find out is to just try it. The problem with putting a patch-like edge cover stitch on a piece of leather is that the stitches are super close together. You'll likely just perforate the leather and it will tear very easily. For putting a border stitch on fabric patches, a merrow machine appears to be the right tool: