Thanks for your concern, guys
I really don't know what else to tell you. I mistyped the lathe, it's a Myford Super 7, which takes an A section V belt on the final drive (four-step cone pulleys, back gear available down to 25 rpm, ungeared up to 2050 rpm)
The belt is definitely the right size; it rides slightly proud of the cast iron cone pulleys, but then so does a conventional A section belt.
They initially sent a B section by mistake, which was completely out of the question in terms of fitting.
The only thing I could think of is that I do ask quite a lot of the lathe sometimes - I've bolted it to a solid slab of heavy plate weighing more than the lathe (in fact, more than me, although that's not saying much), which has transformed a very floppy lathe into a moderately stiff one, and I've developed ruses for peeling off material which possibly were not in the minds of whoever specified the drive.
However, as I say, the "Continental" cog-belt is well able to cope.
I'd be interested to know how many of the posters here are using the traditional link-belt with the metal pegs, and how many are using the slotted item where there is only one type of component, punched from reinforced belting material, which bayonets into another identical piece ad infinitum.
When I say it lasted a couple of weeks, I don't mean it wore out, it's just that my patience wore out.