I had a Braun Multiquick 5 for years and one day it made a popping sound and it was dead. Virtually impossible to repair so I got a more powerful Braun Multiquick 9. I ordered the basic unit only but alas, the fittings don't match with the old attachments. Luckilly, the socket shape and position are identical so a hack is posible.

Quick view of images here (imgur album)

Here's a comparision with the two models : side by side and view of the sockets.

White attachments are old model 7s.

How the new fits vs the old. Motor unit latch does not reach old attachment notch.

Firts, I need to grind out some of the old attachment's fitting to the same shape as the new motor unit. So I printed a sanding block and a "template" so guide the tool. Then sanded it until the motor latches reach the notch.

Printed the actual adapter in ABS (all walls) and press fit it to the old attachment. May need to apply some B7000 to permanently fix it.

It fits like a glove.

Iterations.

Thanks for reading.