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I would agree, in order to work harden something you need to exceed it's yield strength when it moves from the elastic zone to the plastic zone and you get permanent deformation and work hardening which is fairly close to its failure point, relatively speaking and dependent on the material/alloy of course. In theory you can load something constantly within its elastic range and not suffer work hardening issues.

I missed this earlier. The dial isn't going into the holder, it should sit proud of it. This is what I am currently using which I print for each different movement.

I didn't think pulling to set position would work harden the spring, in that position it is stressed where the arm starts. By work hardening i meant rapid polishing at that point, a bit like polishing a pivot work hardens as it compresses the steel. I doubt polishing by hand would achieve much in that respect though. Its finished, arm polished up mostly at the join to the bridge's main body. I'm ok with it, the screw holes aren't great as i had to open them up by redrilling and positioning it was difficult, I'm not much use with a loupe, opening up with a file might be a better option for me or i could just use the correct drill size . And the detent is way too deep, i had to guess that with the stem release out of position and sat on top, but i only took one measure and went for it, no slowly slowly catch your monkey . First go I'm happy , well sort of, it works and thats a big thing for me, next one will have a bit more finesse. Anyone thats interested, after filing, i used a 2000 grade home made diamond micro file and then 20 micron film, the film is much better than wet and dry, more stable to use and doesn't shed cheap grade grit everywhere , then auto polish on a sponge pad.

I discovered this last night when I printed my model, I'll try and tweak the design a little and re-post here

That's very observant of you, Nev & that the 4th wheel is from another movement & has been dished to fit does seem a more likely explanation. Thanks for the education re calculating the rate & spring frequency. In the meantime, spurred by your earlier comnent, I risked a further tinker with the balance spring, cleaning it, fully un-kinking the last few cms (I'd been worried about breaking it first time round) & pinning it at the very end. The clock now seems to be running slow when the regulator is in that position so some progress at last.....Many thanks, once again!

Snap! I recently finished my Gruen 510 movement - though the case for mine is in a rather sad state; I'm going to try re-plating it (in nickel, it's not a gold one). Re. the screws, I got a few of the one gram mixed batches from ebay. I've only needed a couple of screws for things so far, both rare, minuscule types - but both in the mix, after enough time sorting through them! The ones such as normal bridge screws are quite common in those lots.

That's a good idea - shrinking down the nut and wrench size from the old casebook trick!

Glue a nut to the barrel lid, insert a bolt, pull, disolve the glue. Maybe someone will have a better answer.

I printed the base and it is a bit too large to fit on the base of the hand setter. The ring bumps into the column so it is unable to full seat on the central ring. I'm going to try removing some of the materal and see if I can't get it to go down.