IBM Model M Screw, Nut and Bolt Mod

[DDD80]

Late question in a great thread, but I wonder if anyone has tried to countersink the screws?

I have not tried, and I think i will use pan headed bolts instead. But it would probably look even better if I could countersink the metal plate in order for the countersank-headed-screws to be absolutely flush with the surface (like on wood).

Will this be possible or is it just too difficult, especially since the holes in the metal plate are not always circular.

[digital_matthew]

Between the thinness of the sheet metal and the curvature of the backplate I'm not really sure it would be worth it. Now if somebody could do the flush riveting like they use on airplanes that would be something. For what it's worth I use panhead bolts too, but the heads are on the plastic side of the barrel plate.

[DDD80]

Yes, I agree. I mostly countersink in wood and that is quite simple, as long as it is flat. The rivets would look really nice, but I think it would be even more difficult to adjust the tension. I guess it is also easier to adjust the tension with bolts and nuts rather than screws, but that is just a feeling.

But in your case, isn't the head thinner than the washer and the nut? Or why do you install the bolts in that direction?

[digital_matthew]

For no other reason than I find the nuts easier to work with when I don't have to deal with the barrels themselves. Also the panheads have a smaller diameter than the washers, so there's less chance of the barrel plate cracking when they are tightened.

[DDD80]

Ok, that seems logic. I havn't opened my case yet, but according to videos on YT there seems to be a bit space around the drilled hole on the plastic side, so my plan is still to have the nuts and washer on that side.

[fohat]

there seems to be a bit space around the drilled hole on the plastic side, so my plan is still to have the nuts and washer on that side.

I have always done the opposite, because I "tune" the pressure by hand-tightening the nuts with the socket in my fingers, and that would seem to be much easier on the back (metal) side. Fine adjustments are much easier with the socket than with a screwdriver.

I also recommend tightening them to just barely "finger tight" rather than torquing them down hard.

[DDD80]

there seems to be a bit space around the drilled hole on the plastic side, so my plan is still to have the nuts and washer on that side.

I have always done the opposite, because I "tune" the pressure by hand-tightening the nuts with the socket in my fingers, and that would seem to be much easier on the back (metal) side. Fine adjustments are much easier with the socket than with a screwdriver.

I also recommend tightening them to just barely "finger tight" rather than torquing them down hard.

Ok, I think I will have to try myself when I get inside the case.

But do you not have the problem with the nuts + washer making contact with the inner side of the case? As far as I have understood (at least in this thread) that is the cause for using flat headed bolts/screws, since the head is flatter than the nuts + washer.

[fohat]

nuts + washer making contact with the inner side of the case?

My experience has been that you can't use washers on the bottom row, but the others have enough clearance. You could also use a Dremel to grind out small divots where there is contact, since it is probably only a millimeter or less.

And as for that partial row at the bottom edge which many people simply ignore, you can always use tiny self-tapping screws if you are obsessive about it.

And always remember that you are replacing (rather crudely) melted plastic posts with steel machine screws, so you have far more strength than is actually required.

[DDD80]

Finally, I'm done. It took a little while to get the hardware, but now it is completed.

As those who had the washer and nut on the metal side used 8 mm screws, I thought that 12 mm would be good. And for a while it looked good. However, I realised that some keys could not be pressed all the way down, because the bottom of the keycap hit the top of the screw. At first I tried to shorten the screws, but that took some time with the Dremel and it felt as the screws might get too hot and melt the plastic (?). Therefore I decided to put a washer on the metal side as well. This meant that the order became screw, washer, metal plate, rubber mat, plastic circuit x 3, barrel frame, washer and nut. With this solution the screw got seated better, since the predrilled holes were a bit big for the head of av 2 mm screw.

At least it looked good, and I reached the golden ratio (almost at least) that the visible part of the screw should be equal to the height of the washer and the nut.

For the lowest row I had some problems too, because the drilled holes came up some millimeter on the wrong side. So in order to make it a decent connection, I took some washers and cut them in half and used that as a support. Not the best soultion, but good enough. For this row I did not use washers on the metal side, since the space was minimal.

See pictures for some examples (this post typed on the board itself).

IMG_3774.jpg (1.63 MiB) Viewed 6623 times

IMG_3773.jpg (1.6 MiB) Viewed 6623 times

IMG_3772.jpg (1.36 MiB) Viewed 6623 times

The lowest row.

IMG_3767.jpg (1.34 MiB) Viewed 6623 times

[DDD80]

there seems to be a bit space around the drilled hole on the plastic side, so my plan is still to have the nuts and washer on that side.

I have always done the opposite, because I "tune" the pressure by hand-tightening the nuts with the socket in my fingers, and that would seem to be much easier on the back (metal) side. Fine adjustments are much easier with the socket than with a screwdriver.

I also recommend tightening them to just barely "finger tight" rather than torquing them down hard.

I suppose it is impossible to answer, but how hard is hard? I have used the keyboard a couple of days now, and sometimes some keys get "stucked", i. e. the key is not pressed down, but the letter (often a, s or d) keeps typing on the screen. I guess that is because of the tension?! If it is so, should I remove all the screws and start over again, or is it enough to just release some of the screws?

Also, I didnät clean the circuit sheets before assembly, and maybe I should have done that as well.

[fohat]

but how hard is hard?

enough to just release some of the screws?

clean the circuit sheets before assembly

You have replaced thin rods of plastic with steel machine parts - and you only need to keep components in their proper positions, not add tension (and/or compression). Just because you have the ability to crank screws down hard does not mean that you need to do it.

A thorough cleaning of all the interior components is one of the important reasons that I dis-assemble and re-assemble keyboards.

[DDD80]

but how hard is hard?

enough to just release some of the screws?

clean the circuit sheets before assembly

You have replaced thin rods of plastic with steel machine parts - and you only need to keep components in their proper positions, not add tension (and/or compression). Just because you have the ability to crank screws down hard does not mean that you need to do it.

A thorough cleaning of all the interior components is one of the important reasons that I dis-assemble and re-assemble keyboards.

Ok, then I suppose I take it apart again, clean the plastic sheets, and re-assemble.

Do you have any particular method for cleaning the plastic circuit sheets?

[fohat]

Do you have any particular method for cleaning the plastic circuit sheets?

Unless you are having problems you may not need to clean the internals. Otherwise, remember that you are cleaning circuit traces printed on mylar, so if a light wipe with water and a towel or sponge works, that may be enough. Mostly what gets down that far is spilled drinks, and those may be little more than sugar water. Be careful with any solvents that could erode the printed circuit.

As for the machine screws, I recommend that you "tighten" them as little as possible. They are only holding the layers in place with minimal pressure being distributed.

[DDD80]

Do you have any particular method for cleaning the plastic circuit sheets?

Unless you are having problems you may not need to clean the internals. Otherwise, remember that you are cleaning circuit traces printed on mylar, so if a light wipe with water and a towel or sponge works, that may be enough. Mostly what gets down that far is spilled drinks, and those may be little more than sugar water. Be careful with any solvents that could erode the printed circuit.

As for the machine screws, I recommend that you "tighten" them as little as possible. They are only holding the layers in place with minimal pressure being distributed.

I don't think I have problems in general, it is just some keys that cause the problems. But I will try to untighten the screws and see what happends. Hopefully that will be enough.

[DDD80]

Do you have any particular method for cleaning the plastic circuit sheets?

Unless you are having problems you may not need to clean the internals. Otherwise, remember that you are cleaning circuit traces printed on mylar, so if a light wipe with water and a towel or sponge works, that may be enough. Mostly what gets down that far is spilled drinks, and those may be little more than sugar water. Be careful with any solvents that could erode the printed circuit.

As for the machine screws, I recommend that you "tighten" them as little as possible. They are only holding the layers in place with minimal pressure being distributed.

Now I have used it for a couple of weeks and there are still some problems with some of the keys. However, there were not any problems before I installed it in the case. Could it be that since I have washers and head (although flat) on the metal side, these interfere with the bottom of the case and therefore increases tension "from below"?

I have tried to loosen some of the nuts from the other side, without taking it out from the case. My idea was to push the screws down a bit to release tension, but it is impossible to do that, which may be because the screw heads are already against the case.

[fohat]

there were not any problems before I installed it in the case.

There can be problems down at the bottom where the internal assembly gets close to the inside of the case. I have used slightly shorter screws down there, and usually leave out washers in the bottom row. And I have not done it, personally, but you can Dremel out small divots to accommodate the protrusions.

[DDD80]

there were not any problems before I installed it in the case.

There can be problems down at the bottom where the internal assembly gets close to the inside of the case. I have used slightly shorter screws down there, and usually leave out washers in the bottom row. And I have not done it, personally, but you can Dremel out small divots to accommodate the protrusions.

Thanks again!

I have still some problems, but nothing really important. But I wonder on ething: is there a pattern which keys that are working and those that are not? I have tried to loosen some screws, especially those that are near the keys that causes problems (for example, pressing e once turns inte eeeeeeeeeeeeeeee, a becomes aaaaaaaaaaaaaa and so forth), but I cannot see that it helps. Can it be that the pressure is too high on other parts of the membrane than just close to the specific key?

I guess these are kind of tricky questions.

[fohat]

the pressure is too high on other parts of the membrane

That would be my guess. Were you careful with the "crescents" at the hole sites? I understand that they are part of the alignment process.

[DDD80]

That would be my guess. Were you careful with the "crescents" at the hole sites? I understand that they are part of the alignment process.

Yes, at least I thought I was, so I think all of them were unharmed as I removed the plastic rivets. However, now I have began to substitute the washers from under the metal plate. It is time-consuming, but I disassemble the case, remove five screws, remove the washer and then put the screw back again, and assemble the case. So far it seems to work, since the problem has not yet accured again. Then it is the next problems that the screws are too long, at least those that are in the middle of the keys (and thats why I used the washers in the first place), but if everything works I can either buy shorter screws or just let it be. It obviously works with half the screws so far.

[DDD80]

Finally things are getting a bit better. I have tried different methods in order to avoid theeeeeeeeeeeeeeeeeese errooooooooooors, but nothing really worked until I saw in this thread that it is really important the the tension is evenly distributed between all the screws. So I took all apart (again, and again) and adjusted all the screws so that they feel like they are torqued equally, and so for it seemed to do the trick.

Otherwise I had planned to totally cut of the crescents and use a washer or other kind of spacer of the same height as the crescents (which I saw another user had done in the thread) but so far this has not been neccessary.