If your driving end has a pin sticking out, you could always use a shaft collar. Replace the grub screw with a longer bolt that reaches beyond the drive pin. I bought a cheap set  with multiple sizes for the purpose.

Put a bit of packing between the work and the screw in your dog, unless it is massive it will grip 12mm and then the reduced dia no problem.

Alternative is to make a driver from a bit of scrap aluminium.

What Peter Cook says – a brass screw would avoid marking. I’ve also ‘sandwiched’ a bar in a notch between a couple of ali. ‘straps’ bolted together either side, with one as a longer ‘leg’ – wire/tape/zip-tie to a bolt through a face plate..

I think if you want guaranteed concentricity even with ‘de-mountings’ then as you say, B/C is the way to go.

Made from a piece of 1/4 x 7/8 MS bar. Hole drilled 13 mm and filed to shape. Poor photos but I’m sure you’ll get the ideaIs there any way of putting photos where you want them and at a size that I choose ?

Jason said a piece of scrap aluminium would make a simple drive dog. If you have turned one end to size then a simple hole in a piece of metal and some Loctite will make a non-marking drive dog to turn the second end then apply some heat to remove the dog and clean off the Loctite with some acetone.

Martin C

For small parts, I make shrink drive dogs from Ali and have them round. Can either heat them to fit or split them and then clamp with a small capscrew, like an M3. Tap the side the capscrew head will be to M4. With a piece of plate in the saw slot, the ring can be opened up, placed over the end of the shaft and then released. Often, with an Ø0.02mm diameter shrink fit on an 8mm shaft is more than enough clamping pressure. If you decide to want that extra security or make the hole size closer to actual size, then a M3 capscrew can be used to lock it together.

I use M3 with a tapped M4, and also use M4 with a Tapped M5.

Neil

As the shaft is only 55mm long, you could turn it all in one go using suitable tooling, centre one end and use a live centre to support the free end, turn all the diameters, do the the 8mm diameter nearest the chuck with a reversed tool, it will be over length by the width of the reverse tool, part it off, then hold the shaft in the chuck to face off the parted end. No faffing about with making drive dogs, and all done at one setting.

Chris Gunn