Need ideas (or someone to make) a widget to couple motor shaft to M8/M10 threaded rod

[HankMcSpank]

Not really CNC, but hey, it's nice to have a bit of a breather once in a while! (though it is related)

I'm struggling here...I'm making a CNC coil winder (as cheap as chips one with mainly stuff sourced from my box of spares/odds 'n ends), but I no longer have a mini lathe ...else I'd have just tackled this myself.

i need to couple a 1/4" (6.35mm) stepper motor shaft directly to either M8 threaded rod (or M10) threaded rod.

What I'm aiming to emulate is this....



so the idea is to feed enameled copper wire over a helix onto a bobbin ...incidentally, the wire is much much thinner than in the above video (at about 0.15mm->0.2mm dia)...which I think he's exaggerated just to illustrate the method)

The guy in the video used a nylon helix (with what looks like an inner steel core, as bending/deformation would not be good!)...I guess his reasoning is to give a soft 'helix' for the wire to feed over (else there's a risk of the enamel stripping off the copper wire). I've already made a similar effort...I bored M10 threaded rod - but I wasn't very good & it doesn't turn true (there's a fair bit of visible- for want of a better word 'runout' at the end of the helix as it turns!)...that said, it didn't seem to strip the enamel of the copper wire, so I'm not sure it's necessary to go to all the hassle of what the guy has done in the video - also, using nylon would wear out much quicker)

therefore options are...

1. Pay someone to bore out a short piece (15cm) of M10 threaded A2 stainless threaded rod with a 6.35m hole & slide this snugly over the stepper motor shaft.

If not, then my preference is actually to use M8 threaded rod (finer pitch to guide the wire more accurately...also I have a lot of supporting stuff I could use if using M8 vs. M10)

2. Source something like this ALUMINIUM ROUND TUBE 1/2" OD x 1/4" ID x 200mm LONG GRADE 6063 T6 | eBay & ask someone to make some 6.35mm-> M8 threaded rod couplers from it (therefore just bore out the 6.35mm hole to 7mm & tap with M8 - but I'd need this done accurately, which rules me out!)

3. Buy one of these 'off the shelf' couplers .. 6.35mm x 9.5mm Flex Coupler 1/4" to 3/8" Shaft Coupling | eBay (it's 3/8" which is9.5mm...I could tap that & feed in some M10 threaded rod & then the grub scews would hold). I'm not keen on this idea, because obviously it needs me to accurately tap...past history is not good when it comes to me being accurate/square! Also I've no need for the 'flex' ...in fact I'd rather have a straight metal couple with no flex at all.

Edit: Re option 3....I've actually, just this moment found this coupler - http://www.ebay.co.uk/itm/BR-6-35mm-...item5d395a71bf ....6.35mm->7mm coupler) & because the 7mm hole is pre-drilled, even I ought to be able to tap it to M8! This is a good late contender!

Top tips to solve my dilemna warmly welcomed.