IBM Model M - How to go about repairing...

[chet0]

Hello,

I bought a keyboard off eBay and found out that the keyboard had a screw-mod that broke the switch mounting plastic thingy... shown in the pictures... there are plastic cracks everywhere...

I'm trying to figure out the best ways to fix it, and was wondering if anyone has experiencing repairing plastics...

I think the material is ABS or PVC, most likely ABS, cause its black.

I was thinking some kind of adhesive, loctite plastic bonding system seems best or plastic cement... or perhaps, even plastic welding, though I'll need to buy a new soldering iron tip for that.

I've already ordered some bolts, to do a bolt mod... after fixing the plastic.

I want to get this right as I see no replacement for this item from where I live, in Australia. And these keyboards are quite rare, if not impossible to replace.

Any suggestions appreciated.

[E TwentyNine]

Was the keyboard mostly functional before you took it apart?

[chet0]

The keyboard was perfectly functional.

[yui]

The keyboard was perfectly functional.

i feel it is a story of "if it ain't broke don't fix it" but if you really want to i think Unicomp should be able to sell you a barrel plate, their support may be able to tell you what to do, they still build those boards so they may know a thing or two about them, i feel that would be the 2nd best way, 3rd best may be acetone or heat to melt the ABS back together

[rowdy]

You probably can't really "fix" a split plate.  Once split, it loses its structural integrity and no amount of glue or bracing will restore it.

If the keyboard was working prior to disassembly, perchance you could carefully reassemble it and enjoy it as it is.

[fohat.digs]

Cracks may be irrelevant with screws holding the plate in place and in alignment. I have always encouraged people to turn screws "just barely finger tight" since they are orders of magnitude harder and stronger than the plastic posts that they replace. I would bet that the cracks appeared as the screws were torqued down much harder than necessary.

Old-fashioned model airplane glue (the infamous kind that people used to sniff) has worked for me on Model M barrel plates. If it were me I would loosen the screws to what seemed "just enough but not too much" and lay a light bead on the cracks.

[chet0]

Cracks may be irrelevant with screws holding the plate in place and in alignment. I have always encouraged people to turn screws "just barely finger tight" since they are orders of magnitude harder and stronger than the plastic posts that they replace. I would bet that the cracks appeared as the screws were torqued down much harder than necessary.

Old-fashioned model airplane glue (the infamous kind that people used to sniff) has worked for me on Model M barrel plates. If it were me I would loosen the screws to what seemed "just enough but not too much" and lay a light bead on the cracks.

I've gone to the closest hobby-shop and  got some Plastic Glue, Tamiya ABS and Plastic Weld (I am a bit dizzy from the fumes). I'll do it properly tomorrow outdoors.

You probably can't really "fix" a split plate.  Once split, it loses its structural integrity and no amount of glue or bracing will restore it.

If the keyboard was working prior to disassembly, perchance you could carefully reassemble it and enjoy it as it is.

It was working, but upon disassembly I noticed some of the flippers shifting... I gotta close the big splits.

... 3rd best may be acetone or heat to melt the ABS back together

I'll do that if the glue fails to hold.

[E TwentyNine]

Cracks may be irrelevant with screws holding the plate in place and in alignment. I have always encouraged people to turn screws "just barely finger tight" since they are orders of magnitude harder and stronger than the plastic posts that they replace. I would bet that the cracks appeared as the screws were torqued down much harder than necessary.

Old-fashioned model airplane glue (the infamous kind that people used to sniff) has worked for me on Model M barrel plates. If it were me I would loosen the screws to what seemed "just enough but not too much" and lay a light bead on the cracks.

I have an M13 where I had to mount a new trackpoint on it, used two part liquid epoxy for that, worked great.  It had a small crack as well, used the same epoxy letting a little seep into the crack and a bead across the surface.  Hasn't gotten tons of use but it has held up for years.

[chet0]

Here's the result of the mostly glued up part. It's not pretty, but it seems functional... a few things I noticed, the part actually needs to flex a bit... to fit into its original place, and while doing a practice fit, there were some cracking sounds, but upon inspection, nothing seems cracked. So it's good enough.

I avoided expoxy because I had a lot of places to glue up, and I didn't feel confident as I haven't used it before.

I'm actually surprised at how well the glue is working... the small pieces that broke off at the bottom are holding really well.


I' ordered the bolts and nuts for the bolt-mod 2 weeks ago, so it'll probably be a while before I get the parts.