Yes, indeed! Some stitches from the model 66.
I have been puttering around and poking into the working parts of the machine to get an idea of it's workings. I've also done a fair amount of web surfing looking for anything and everything about this old sewer (isn't the English language just awful sometimes!).
Since the machine hasn't got a belt, I've been running tests by turning the crank by hand. Preliminary results indicated a problem. The top stitches looked great, but the bottom was a mass of loops (made with the top thread) and a bottom thread that simply ran through the whole lot.
First samples showing the bottom side of stitches:
Turning the top thread tensioner to it's highest setting helped a little but not enough; the loops shrank but did not disappear.
Close observation of the bobbin mechanism showed that the top thread was getting wedged between the bobbin case and a small metal plate as it wound around the bobbin case. It seemed that the pull of the thread caused the case to shift thereby applying pressure at the point where the thread should pass between the metal plate and bobbin case. This created too much tension on the thread which nullified the action of the take-up lever above, the result being these loops.
"Hm.", I thought. (Such a ubiquitous thought.) I wondered whether there was a fault in the bobbin case causing it to shift. As I watched closely this afternoon something else caught my attention: The hook assembly's (in which the bobbin case rides) rim seemed to be a bit gunked up with something. With a swatch of cotton and some sewing machine oil I wiped it off and applied a touch of oil to a few of the moving parts. Aha! This alleviated most of the shifting of the bobbin case. Apparently it was getting stuck to that gunky stuff which pulled the case along, shifting it enough to wedge the thread between it and that small plate.
Hard to believe that a little oil and cleaning could have such a huge effect. But this is what the underside stitching looks like now:
That's more like it! A little tensioning adjustment should make these stitches just about perfect. For the record, here's the top-side stitching (sorry it's white-on-white):
This is all getting very exciting.
The bobbin plate arrived today along with the new drive tire for the bobbin winder. Here's the old tire followed by a pic of the new tire in place:
The new plate fits. Unfortunately, it is matte finished, whereas the original is glossy. Not really a big deal, but it's noticeable. I'll keep my eyes out for a glossy one.
All I need now is a belt and will order one tomorrow.
This page came up in one of my searches. I like that it points out all the oiling points, something that the manual I ordered does not show--to my surprise. (If you look at this page where it describes the working of the oscillating hook, the problem I was having was occurring between steps 2. and 3.)