Singer 108WSV36

[Constabulary]

6 hours ago, brongle said:

so it should able to drive a swinging attachment plate. 

yes, there is a short pin on the underside of the swing plate that goes into the slot in the feed dog and the moving feed dog governs the swing plated.

7 hours ago, brongle said:

Any idea what the slot engages with, if anything? I couldn't feel much in there with the screwdriver, and the below is definitely a bit simplified. One thought that comes to mind is that it might act as a sort of flexure brake, expanding slightly against the inside of the driveshaft when you tighten it to keep it from shaking loose and reducing the stitch length as you sew.

 

It engages with nothing. You can put a screw driver in the slot and with a little twist you can widen the slot a little bit so you have more friction between the spindle and the inside of the drive shaft and that IMO is for holding the spindle in place otherwise it could probably move and alter the stitch length. That what I think.  😉

[brongle]

13 hours ago, Constabulary said:

It engages with nothing. You can put a screw driver in the slot and with a little twist you can widen the slot a little bit so you have more friction between the spindle and the inside of the drive shaft and that IMO is for holding the spindle in place otherwise it could probably move and alter the stitch length. That what I think.  😉

Gotcha! That makes a lot of sense. 

[friquant]

On 3/1/2026 at 5:52 PM, brongle said:

Re: your (double) note there - do all rotary hooks rotate twice per stitch cycle? All three of my machines definitely do. Didn't realize you could end up grabbing the thread twice, but that makes sense. 

I think modern rotary hooks all rotate twice per stitch cycle. The ones I've seen accomplish this using gears. But imagine a machine with a rotary hook that uses only eccentrics to accomplish motion---those are the ones that I suspect only rotate once per stitch cycle.

As a reference here is a reply to one of my posts on another forum in which the collector Unknown Artist states: "rotary hooks (Wheeler Wilson system) run smoothly. They are wear-resistant, fast, and reliable, but louder than double-rotary hooks. (Pfaff)". 

That was the first I had heard anybody mention single or double with the word rotary. I would like to obtain a single-rotary because I'm curious about the mechanism. Even if it's a domestic machine. I suspect that the White Rotary from a hundred years ago is single rotary, so I have my eye open for one of those.