Model M Threaded Insert Mod (No more bolts and nuts!)

james.kim13

25 Sep 2019, 21:19

Hi guys,

First time poster here,

I am currently in a process of restoring couple of IBM Model M 'Blue Lables'. Unfortunately, the plastic rivets are starting to fall off one of them and starting to loose keys, necessitating the repair.

Having a bit of experience in mechanical design in automotive and consumer electronics, I have decided to use a threaded inserts for plastic instead of bolts and nuts (Seems like a pain in the ass).

I like taking my keyboard apart every once in a while and washing all the gunk out with soap and water. Therefore, screw mod was a no for me.

I ordered these parts from ebay for about 3 Canadian Dollars shipped (which is equivalent to about 0.004 US Dollars at the time of the writing)
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I only needed 1 of 8mm M2 screw for guiding the threaded insert as shown in the next step.

Threaded inserts are normally molded into the plastic piece however, it can also be easily pressed into place with a soldering iron.
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I used my often abused Hakko Iron for this job.
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I cut the plastic rivet off and drilled a 2.5mm hole as you would for any other mods. then, threaded a 8mm M2 screw, a couple of threads into the threaded insert

Link to IBM Bolt and Nut Mod - viewtopic.php?t=9169

Then, take a hot soldering iron press directly down. (Temperature isn't super important. The goal is to heat up the the insert as evenly as possible while applying downward pressure. I just used the maximum setting for my Iron)
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Initial results are very promising.
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From the other side, you can see the small amount of plastic that has been displaced and created a bit of a bulge on the other side.

This is very desirable as the threaded insert does not poke through the plastic.
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Now I just have to do it a million more times.
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Going forward, I may decide to add some super thin M2 washers. But now I will be able to take this thing apart easily and clean it whenever I want.

I may also leave some rivets unshaved in place to aid positioning of the rubber damper and plastic membranes during assembly
Last edited by james.kim13 on 26 Sep 2019, 03:10, edited 1 time in total.

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Muirium
µ

25 Sep 2019, 22:39

A fine technique and first post!

Once you undo a screw, does it slide right back in when you reinstall it later? I imagine the melted plastic surface is a nicely matched corkscrew shape now. Hopefully all your screws are uniform enough you don’t have to match them perfectly to their respective holes!

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JP!

25 Sep 2019, 22:52

This looks to be very promising. Might be the new best way to keep our heirloom Model M going for generations. Of course the plastic barrel plate could always crack on it's own but of course always replaceable.

james.kim13

26 Sep 2019, 00:41

Muirium wrote:
25 Sep 2019, 22:39
Once you undo a screw, does it slide right back in when you reinstall it later? I imagine the melted plastic surface is a nicely matched corkscrew shape now. Hopefully all your screws are uniform enough you don’t have to match them perfectly to their respective holes!
Thanks for the warm welcome.

I drilled the hole slightly oversized (2.5mm for M2 screw). The melted plastic does not fill the hole as the insert is pushed into the hole. The M2 screw slides in and without threading into the plastic at all.

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