Success at last!  Thanks everyone for the range of options -- I was amazed at all of the ideas, most of which I had never considered and/or thought impossible.  

I started with the simplest, Mark's suggestion of driving a 1/4" hex into the rounded off 6mm socket.  All the while trying to keep in mind the caution that I should not hammer to hard -- I addressed that in part by using an 8oz hammer with lots of small taps.  This almost worked but the metal gave at the last moment. 

So onto the next simplest -- Karl's suggestion of using a 8mm Triple Square bit (I think the one I used is triple square, it has about 12 splines? Torx has around 6 splines, if I'm correct.) That worked!  Came out so smoothly I suspect the 1/4" drive attempt just before helped to break it.

I had played around on the bench with using a 12-point 12mm socket.  I think that too would have worked but I would have had to hammer quite a bit harder to get it on.

Anyway, now onto replacing the joints.  Which I am going to have to do judging from the pitting on the ball hubs and races.  Our local dedicated VW parts shop has these https://vanagonwestfaliaparts.com/products/cv-joint-kit?variant=29737033793 at $95CAN, which is very roughly equivalent to $65US, and I can pick them up.  I think they are Lobros but I will need to confirm that.

Thanks again for the help.

Rick

On Mon, Jan 1, 2024, at 10:49 AM, OlRivrRat wrote:
>         I’m not familiar the hammering in of an allen or torx bit but the amount of
> 
> hammering on that is needed to secure a socket on the outside of the bolt head
> 
> is surprising slight & I am somewhat sure that longitudinal forces that happen
> 
> upon the Axles are arrested by thrust bearing surfaces & probably not the roller
> 
> bearing chases but even if I’m incorrect on that point, the Axles have some end
> 
> play when properly installed so what ever it is that they hammer up against on
> 
> the kinds of drives We like to subject them to can apparently take a beating ~
> 
> 
> > On 1 Jan , 2024, at 8:24 AM, Ray Brubaker <rayandmerle@GMAIL.COM> wrote:
> > 
> > Be aware! Any hammering on this bolt goes through the ball bearing that is
> > part of the wheel bearing system. Heavy hammering can cause the balls to
> > dent the races causing shorter bearing life. These are robust bearings but
> > no bearing should be hammered on if you want it to have a long life.
> > 
> > Ray
> > 
> > On Sun, Dec 31, 2023 at 9:15 PM Mark Drillock <madvws@cox.net> wrote:
> > 
> >> The 6mm allen bit is slightly smaller than 1/4".
> >> I buy a 1/4" allen bit, file a slight taper on the 6 edges of the tip.
> >> Then hammer it into the rounded out 6mm hole, using heavy blows.
> >> Then unscrew the bolt.
> >> 
> >> VW used many 6mm allen bolts on many of their vehicles.
> >> I have used this method lots of times, including CV bolts.
> >> 
> >> Mark
> >> 
> >> On 12/31/2023 5:08 PM, Rick Cooper wrote:
> >>> Hi all,
> >>> 
> >>> I've got a noisy CV joint and thought I would remove and repair it
> >> today.  But I managed to round off one of the twelve 6mm Allen socket-head
> >> bolts so that I cannot break the last bolt free.  Unfortunately it is on
> >> the outside CV joint so it inaccessible by most tools.
> >>> 
> >>> Has anyone had this experience and can offer any advice?  Am I stuck
> >> drilling out/off the head of the bolt?  And then how do I remove the shaft
> >> from the wheel assembly since it will be challenging, even with joint out
> >> of the way, to get a good hold on it with vice-grips?
> >>> 
> >>> Thanks for any help.
> >>> 
> >>> Rc
> >> 
>