Looks About Right.
I wasn't going to dump the starter motor just because the drive coupling was U/S, so I searched on the web for some clues as to what else used this particular setup.
I discovered that Triumphs TR2 - 4A had the same part - no.501217 for anyone else in the same hole - but at a price: around £55.
Once the Bendix was removed (a circlip holds it in which when released, disappears into the darkest corner of the workshop) and the spring retaining spacer unscrewed after easing back the tabs set into recesses in the shaft - note that the spacer is a left-hand thread - the Acme threaded portion can be eased off the shaft and the coupling sleeve withdrawn.
The problem is perfectly illustrated here - portions of the rubber had been ripped away as the vulcanising gradually failed, allowing the centre sleeve, Acme thread and Bendix to rotate independently of the coupling sleeve which would otherwise lock in the drive to engage with the starter ring.
I can't tell you how much time and trouble this bench shear has saved me. It's got to be one of the handiest bits of kit I have. Setting about the reproduction of the 6/80 radiator's lower support, I decided to cut a strip of 1mm steel sheet (the original was about 1.2mm) and begin by folding it into a channel with surplus either side for the second flange and leave the trimming for later.
I didn't use the bead roller as with the various wheels I've got, nothing would achieve the profile of the bends in the channel. I put a radius on a piece of flat bar and got out the hammers.
The channel turned out slightly deeper than the original - by only a couple of millimetres - and I don't think it's going to matter as the channel should be filled with a special water-retaining felt padding material favoured by British car manufacturers of the period (and the cause of the corrosion in the first place). I'll use anti-vibration matting which doesn't accumulate moisture or disintegrate over time.
Though not as good as having a twenty-ton press and a die, the hammering and subsequent trimming achieved a respectable and perfectly serviceable piece which can be easily tidied up after bending and before painting.
Getting the jig right for the bending took a bit of time and once nailed down, heat was applied to the corners and the surplus carefully pulled around the steel pegs, taking time to let the metal settle into its new position and avoiding the worst of the creasing at the corners.
Everything went more smoothly than I expected. A little bit of tweaking to neaten up the corners and no one will know the difference.