Rotating handlebars

So I've put my latest project together, and went for the first test ride.

The handlebars slipped/rotated, odd, I thought, I'm sure I tightened those.
Sure enough the raised centre part of the bars, with the nice engraved GB logos is clamped firm and tight. The rest of the bars can rotate through this.

Boody wierd. These are from ebay, 60's GB randonneur bars in otherwise good condition. Has any one else ever suffered this?

I guess I'm going to have to drill them, tap them and put a bolt in, unless this is some 'feature' of old rando' bars that no one ever told be about.

is the 'raised bit' like a sleeve? it might've come loose from the main bit of the bar?

I would not drill through bars as I would worry the hole would be a perfect place for a crack to propagate.

Yes it is a sleeve, must have been bonded with something not tested for 40 odds years worth of working life. Shoddy manufacturing!
Not cold, so shrinkage is unlikely.

Prancer, a neat round hole is /usually/ okay, after a nice uniform bit of material it's about the least stress riser-like thing you can have - which is why you drill them at the end of cracks to stop them spreading. Also, these are going to have a very gentle life.

hmm, i don't understand gentle

my bikes tend to get fairly abused

Have you thought about getting a TIG welder and welding the sleeve to the bar?

Araldite the fucker

buy some new bars that aren't broken

All sterling suggestions, chaps, but I've just spent three evenings shining the bastards and sewing up my VO Elk Scrotum grips, so I'm not taking the bars off, no matter how broken/unfit for purpose. I guess I'll just mount the bike on the wall and forget about it. Sniff.