MadModder

Very sensible suggestion Mike. Similarly I'll make my packer pieces a loose fit in case the ends bell over.

Still waiting for some 12.9 grade bolts to use as potential extractors, but in the mean time I've tapped those two 9.9 mm holes out to 7/16 20 TPI. 15 threads so 3/4" deep should give enough thread engagement I hope.

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There seems to be a distinct ridge in the hole about 25 mm down as though the front disk in the centre of the tool disk is a separate part - perfectly possible that the bolts trap it against a flange I suppose. Can't get a decent picture down the tapped hole but it's more visible removing one of the holding bolts.

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If the bolts arrive tomorrow all should be revealed

No need to tap full depth ,go as deep as possible and insert a small piece of brass bar at the bottom of the hole and wind the bolt onto that .   Mike

Thanks for your thoughts chaps.

I have a feeling that the tool disk currently on the lathe will be easier to dismantle than the broken spare one but I'd still like to get that apart first to see what's what. Latest plan is to lug out my rather heavy magnetic drill (it's old school not Temu!) and drill out the broken off bit and tap those outer holes for a strong 'push off bolt'.

Need to do some careful measurements to stop the drilling before breaking through into the main casting and either create a flat bottomed tap, or push off bolts with reduced ends to pass through the inevitably tapered end of the tapping.

Why does everything get so complicated !

OK last resort - what does the drawing say ? Well the only drawing that I have is from the Patent Application so may not be 'as built' but here it is:

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Now to me that is clear as mud. I can see the large bolts screwing into the outer half of the front curvic coupling allowing for a bit of rotational adjustment (as I have previously done). But the ten smaller bolts from the way that I'm reading the drawing don't seem to do anything.

I've retreated for more head scratching.

As best I can tell, and I'm not much cop at interpreting those kind of drawings either...

The smaller bolts look exactly like the pattern that typically holds a car flywheel to the crankshaft. My best guess would be that if you undo and remove them all, you then screw bolts into the two holes top & bottom & use them to push the whole front piece off. Or maybe just the middle comes out, since the drawing shows all the bolts flush with the same surface, but neither physical unit matches that (the centre bolts being further in). Best guess, the big outer bolts are holding the coupling together (with,as you say, enough play to make minor radial adjustments), the inner bolts are what's holding it together. Probably gravity isn't strong enough to overcome the sticktion between the two parts, hence the push-it-out bolt holes in the centre portion.

Should be easy enough to test the theory - loosen the inner bolts, screw a bolt into one of the things you suggested might be for a slide hammer, and see if a) it bottoms out and b) if so, that it does indeed dislodge the coupling.