Tony said > On Sat, Sep 12, 2020 at 6:41 PM Adam Thornton via cctalk > <cctalk@classiccmp.org> wrote: >> >> I got an LK201 recently that was a little damaged in transit. A couple of >> the keycap assemblies and their corresponding leaf springs have come off. I >> can see how the leaf springs fit on the little posts on the keycap >> assemblies, and I can see where those snap into the board, but what I don’t see is how to get that put together and then keep it together while I turn it over and then get it in place.>> >> Clearly there is some simple trick I am missing. What is it? > > When it was made, those posts were much longer. After fitting the leaf > springs and fitting the unit to the membrane/chassis plate, the posts > were melted and formed over to make a large 'head' that held it all > together (this is commonly called heat staking). > > My guess is that the formed over part has broken off (you might find > some little white disks of plastic, about 1/8" diameter, rattling > about inside the case). Alas I have never found a way to re-fix them. > There's not enough plastic in the housing to drill it out and fit > screws/nuts. There is no way of gluing something to the ends of the > posts that would be strong enough, > > -tony >
Perhaps using a 3D printed jig, I would set up the key post in a lathe collet and drill a sub-millimetre hole through the axis. Then glue a sliver of carbon fibre rod in, lastly mill some channels a few thou deep along the outside of the post for binding with a strand of de-braided Kevlar thread to hold the end on. A tiny drop of cyanoacrylate applied with a sharp toothpick keeps the Kevlar in place. The end cap would be drilled with the same drill. I've used this CF+Kevlar method for repairing a number of things where there is not enough surface area for adhesive alone and I am sure the repairs will outlast the items I've fixed. It takes some patience and a need to set up the job reasonably carefully. Steve.
