Threading the machine:  It threads simply enough - but oddly (because it uses just a plain old hole in the machine as one of the thread guides).   There is another unknown hole nearby, & I'm not at all sure it's not supposed to be used, too, but the machine I saw threaded online didn't use it, & when I tested it this way it worked very well, so for now, I'm just going with what worked.   (I'm thinking it may be there to allow the thread to bypass the tension rings, by going under it - but that seems a recipe for disaster to me.)   Feel free to fiddle around with it, as you like.  

I'm just fumbling along, doing my best - just like everyone else.     : )

Needles:   I'd read that these Smith & Egge's use the Wilcox & Gibbs Needles, but I have some, & could not make them fit (too long).   I did have some shorter Singer Toy needles, so I tried one, & it fit perfectly - lengthwise, but the top is fiddly to get it aligned just right.   Just align the needle hole sideways, with the flat part of the shaft (Top & near the needle hole) facing the looper, so the looper passes to the INSIDE of the needle, just scraping the flat part on it's way by. That will allow the Looper to grab the thread on the way by.  That's the most important part for it to work.

Fortunately, Singer Toy Needles are readily available on Amazon, and also fit the Singer-24 Series of antique sewing machines, as well.   Last I knew they were about$10-13. for a 20-pack.    Pricey, but oddball needles always are (sigh).

Tension Adjustment:  This tensioner works simply by the Needle bar going up & down, with the bar that drives it also coming into contact with a spring loaded Tension Pin that tightens and loosens the tension plates as it goes.  It's incredibly cool, the way that it works, as you can only see part of the works from the outside.  

Inside the Tensioners' tower, there is a Spring loaded Inner works, as well, so as it pushes up to release the tension on the outside spring, it increases the tension on the Inner Spring as well, forcing it right back into position, without needing to hope gravity is on your side.    Very cool - as is the Nut & Screw that you can see, but don't immediately grasp as even being a Screw or Nut. 

Tightening the screw & nut increases the pressure on the springs, so if you feel you need to adjust the tension, you can just tighten or loosen the nut, or the screw head.  Both are free now, but in time, that may change, so know you can simply insert a small nail into the hole on the bottom of the screw, while holding the nut from above from turning.  You'll think you need a special tool to do it, but it can be done with just a screwdriver on the nut (holding only one side), and a small nail to turn the screw below the tension stack.   It's very slick, & took me a minute to figure out what they'd done, but once you get it, it's easy.

Show & Tell Below:

Stitch length adjustment lever:  It works simply by sliding the lever up or down to lengthen/shorten the stitches, but the stitches are so fine my old eyes can barely see them anyway, so absent magnification, I'm hard pressed to say stitch length really matters.   Here's my sample stitching, sewn one side up, then flipped, so you can see both sides of the stitching on one side.

Bottom = "Loops" of the chain stitches.  Top =  just looks like ordinary stitching on any machine.      TINY Stitches, though.