IBM Model M - Any tips on gluing a chipped case?

bjarke15

21 Mar 2020, 14:06

Does anyone have experience with gluing a chipped or cracked model M case?

I recently acquired a board where the case has suffered some chipping (pic included). Luckily the chips fell inside the case, so I’m planning on gluing them back.

It’s a 1391407 (danish model from 1995). The case has not yellowed noticably, so my guess is that it is PVC and not ABS. I can’t seem to find any clear answers, however. This leaves me unsure on how to best glue the chips back, since this depends on the type of plastic.

This is why I would like to know if anyone here has tried gluing a model M case back together and has some tips on the procedure.

Attached is a picture of one of the chips.
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Blaise170
ALPS キーボード

21 Mar 2020, 14:43

I've never glued a keyboard case but I've done some minor work with plastic and found epoxy works quite well and will likely hold better than glue would.

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swampangel

21 Mar 2020, 15:04

So far my favourite for repairs of non-force-bearing plastic is https://www.amazon.ca/Tamiya-FBA_87038- ... B000BMYWYC

Quick set, strong bond, and produces an almost invisible seam if you get the parts fitted properly.

I've also had some luck using E6000 glue to put a replacement stem on a PBT key from an Apple M0116 and 2-part epoxy when working on my own version of viewtopic.php?f=2&t=21198&p=439870

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SneakyRobb
THINK

21 Mar 2020, 15:08

Hi,

Halfway down through this thread from fohat.digs there is a section about fixing a Model F case which is similar

https://geekhack.org/index.php?topic=48786.0

bjarke15

21 Mar 2020, 15:21

Thanks for the recommendations! I'll try to get my hands on some Tamiya Extra-Thin Cement. Apparently it works by welding the plastic together, which should produce a more seamless transition between pieces and not leave any residue like epoxy might.

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swampangel

21 Mar 2020, 20:02

Example of an Apple M3501 abs spacebar that had 2 pieces broken out of it, repaired with the tamiya cement:

Image

Image

I didn't do a perfect job but, at a glance, it just looks like the plastic is scratched. You could take it further with a bit of sanding and maybe some filler product.

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fohat
Elder Messenger

21 Mar 2020, 20:21

bjarke15 wrote:
21 Mar 2020, 15:21

I'll try to get my hands on some Tamiya Extra-Thin Cement.
The space bar was probably ABS but the Model M case is PVC, a more difficult plastic.

My Model F guide repaired a case that was broken through, but the reinforcing brace on the back side was helpful. Just be careful that you don't interfere with anything on the inside.

JB Weld now makes a clear epoxy that would be cleaner than the original formula in your situation.

Findecanor

22 Mar 2020, 00:33

swampangel wrote:
21 Mar 2020, 15:04
So far my favourite for repairs of non-force-bearing plastic is https://www.amazon.ca/Tamiya-FBA_87038- ... B000BMYWYC

Quick set, strong bond, and produces an almost invisible seam if you get the parts fitted properly.

I've also had some luck using E6000 glue to put a replacement stem on a PBT key from an Apple M0116 and 2-part epoxy when working on my own version of viewtopic.php?f=2&t=21198&p=439870
"Plastic cement" is mostly thin running solvent. I find it works great for flat surfaces of ABS made to be pressed together but less well for repairs — where I'd often need some additional plastic to fill the gap. (Not that I didn't repair my humidifier with only thin cement earlier this week...)
Sometimes I use a stick of the same material, get solvent on that and then smear the softened stick onto the surface, just to get some more plastic in the crack before I glue the parts together.

I'm also not sure if styrene cement works on PVC. I think is mostly ethyl acetate. PVC glue I've bought (for use with ABS), I found in the plumbing aisle in the builder's supply store, and it contained MEK (Methyl Ethyl Ketone).
Note that with any type of solvent-based cement/adhesive, there will be marks afterwards: crack and/or a raised ridge, and if you're not careful: a fingerprint (...). If you'd use epoxy, you could wipe away excess uncured glue with water or alcohol (depending on the brand).

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