Fitting a regulator arm ring to a stud ring...help please

[AlecMac]

Good morning, I'm really struggling with this and have run out of ideas.  I've got a eta 1080 missing it's regulator arm, replacement was easy and cheap to get hold of, but I need to fit it over the inner lip of the stud ring on the right of the pic. When I pinch the stud ring closing it's gap they are both the same size. So to get the regulator arm on I need to hold  the strut ring closed, hold open the regulator arm ring in a manner that means I can still fit one onto the other. At a loss. I've all the usual watch making tools available, apart from a lathe...I can picture a jig that would do the job. I hope someone has a clever trick!

Edited June 11, 2024 by AlecMac
typo

[rehajm]

1 hour ago, AlecMac said:

can picture a jig that would do the job.

Is this a not enough hands problem? Maybe trying to pinch the stud side in a vise? Tack it to one side with a drop of hot glue or gs cement or a tiny bit of folded painters tape to hold the stud ring  while it gets pinched in place? Would need to have the top side of the stud protruding to accommodate the regulator side. I suspect you wouldn’t need much pressure to keep the stud closed while you stretch the regulator ring…

…or maybe an oiler sized drop of glue will keep the stud ring closed, fit the regulator then dissolve the glue?

Here’s my vise..

Edited June 11, 2024 by rehajm

[AlecMac]

Thanks rehajm