Yet Another Bolt Mod

[an_achronism]

That better not be a pube.
THE PROBLEM

I grabbed a 1990 Model M recently which has some pretty bad issues with a lot of keys:

• Some of them actuate prematurely, such that the key registers just before the spring fully buckles, which sometimes causes double keypresses (or, worse, "stuck" keypresses that keep repeating even after the key has physically reset)
• Some don't buckle properly, but changing the keycap stem makes them work fine (stops working again when I put the original stem back on)
• Some don't buckle properly, or rather they do buckle but feel soft and mushy as hell
• The right Shift key also had the worst binding I've ever seen, it just stayed down every time you pressed it

TROUBLESHOOTING

I started by giving it a thorough but careful clean without pulling the assembly apart, because it had almost every rivet intact, surprisingly enough. I was hoping I'd be able to save it without wrecking that, but it seems not.

I managed to more or less sort the right Shift with a combination of thoroughly cleaning the stabiliser and very carefully putting pressure on the key's "leg" to reposition it by a fraction of a millimetre, which seems to have done the trick.

The keys that weren't buckling unless I swapped out their keycap stems seemed to have slightly screwed up spring-holder "nubs" inside them, so I guess they weren't holding the top of the spring in the right position. No biggie, but weird, 'cause presumably they were always like that and it's a manufacturing screw-up, which surprises me!

As for the keys that were actuating early and double-pressing / getting stuck, It doesn't seem like any amount of fiddling with springs and so on is helping, but there was clearly still dirt that I couldn't clean off very easily so I began to wonder if maybe there could be corrosion somewhere internally that I couldn't see/fix without pulling the assembly apart. So, with much sadness, I clipped all the plastic rivets off (some dropped off basically the moment I touched them, so it seems they were about ready to fall off anyway, at least) and pulled the assembly apart.

I'm almost annoyed to discover that there is no corrosion or any other kind of damage/dirt whatsoever that I can see on the membrane within the assembly, but at least that's ruled out. The rubber mat that the flippers push into did have quite a lot of muck on it though, so I suppose it might simply have been that dirt was stuck underneath some of the flippers and that was causing the premature actuation on some keys, I don't know.



I also notice that several springs were rotated slightly wrong, such that the end of the coil was to the side instead of the top of the switch assembly (as almost all of them were) which I suppose might be part of it as well...


There is quite a lot of corrosion on the part of the membrane that was outside of the main assembly (the tabs that go into the controller PCB), but I don't know if that would necessarily explain the behaviour I was seeing:


I suppose in theory it could be that the keys with the intermittent stuck actuation issue might all be correlated in the matrix, in which case it could be that the trace they use on the membrane tab is the same one and has been affected by the corrosion. If necessary, I might replace the membrane entirely, but I'm going to do my best to clean off the corrosion first (as it stands, I've run out of cotton buds, hahah).

If nothing else, this at least let me clean everything much more thoroughly (I actually blasted the barrel plate under the shower head, it was so filthy). So there's that.





HARDWARE

This will be the first time I've done a bolt mod, so I've been trying to grab as much info on it as I can find. I'm finding that people seem to do it slightly differently, and I recall finding at least one reference to using locking nuts to prevent them popping off and creating a short, but I can't seem to find that again and from what I can see it looks like most people don't bother and just use ordinary M2 hex nuts. As it stands, I'm considering using these machine screws, these washers, and deez nuts, which I could theoretically pair with jam nuts (ow) to discourage them from falling off. However, that might not have enough space in the assembly (or on the screw) to work, so I might be better to use nylon locking nuts instead.


Any advice from the more experienced bolt modders amongst you?

[fohat]

If you can wait 3 weeks you can get Chinese hardware on ebay for a pittance. "Quality" is not really important since you are replacing common cheap plastic with steel so your new "strength" will be orders of magnitude greater in any case.

At the front (space bar side) there is very little clearance between the internal assembly and the case, so it can be a difficult squeeze. I usually don't even try to use washers in the first row or 2, even though I prefer to use them whenever possible. Once you start curving up from the bottom there will be plenty of room for fancy double-nutting and whatnot, but why?

Also, don't make the mistake of over-tightening your nuts just because you can. You only need to keep the layers in place relative to each other.

[an_achronism]

If you can wait 3 weeks you can get Chinese hardware on ebay for a pittance. "Quality" is not really important since you are replacing common cheap plastic with steel so your new "strength" will be orders of magnitude greater in any case.

I don't think I can, mostly because I have the spring switch assemblies lying on a sheet of cardboard in the living room... I did find fittings on Banggood though, and they are indeed cheaper than the linked ones.

At the front (space bar side) there is very little clearance between the internal assembly and the case, so it can be a difficult squeeze. I usually don't even try to use washers in the first row or 2, even though I prefer to use them whenever possible.

I've even seen some guides saying not to bother putting bolts in the bottom row at all, so that checks out.

Once you start curving up from the bottom there will be plenty of room for fancy double-nutting and whatnot, but why?

As I said:

to prevent them popping off and creating a short

Also, don't make the mistake of over-tightening your nuts just because you can. You only need to keep the layers in place relative to each other.

Aye, even with only 3 rivets missing I could see that there was still actually some give in the assembly: if I squeezed it with my fingers, the barrel plate moved a bit. I did that before disassembly to check roughly how firm the fit actually was. I've seen mention of problems caused by over-tightening.

Thanks!


Here's something specific I've been wondering, by the way. Every guide I've seen seems to put the screws in from the top, with the bolts on the underside, against the metal backplate. Is this for good reason beyond just trying to make it look tidier underneath the keys? I'm wondering if it might actually be slightly easier to fit the screw heads into that bottom row than trying to fit the bolts there. Plus, you could theoretically see if any of them were loosening without opening the case, and be able to adjust them to some extent without opening it as well. But depending on clearance, I suppose the ends of the screws might end up hitting keycaps when you press them, in which case that would presumably be why everybody seems to do it the other way. Anybody tried flipping the orientation of the screws around so they're more or less upside down, going through the assembly from the underside and out the top?

[fohat]

I've even seen some guides saying not to bother putting bolts in the bottom row at all, so that checks out.

There is the "first row" roughly under the space bar, but there are a few screws below that, practically at the edge. These are problematic because there are "fins" of plastic that get in the way regardless. The ideal way to fix those is to run the screw up from the bottom without worrying with a nut (with a 1/16" drill bit and M2 screws, the threads cut their way in with little effort) or, even better, get half a dozen even smaller self-tapping screws for that area. Since the space bar has considerable leverage and it is likely to get pounded, I would not ignore the bottom edge.

I always install the screws from the top down because it makes adjusting the nuts far easier if you plan on "tuning" the compression. Also, it does look much better.

[Obin]

There is the "first row" roughly under the space bar, but there are a few screws below that, practically at the edge. These are problematic because there are "fins" of plastic that get in the way regardless.

My solution to the bottom row is (carefully) pushing 5mm bolts down through the fins with a soldering iron until they are at the level of the lower plastic ledge. 5mm bolts work out nicely if I don't put any washers on the bottom. There is no contact between the nuts and the bottom case.

[an_achronism]

Update: went for a handful of self-tapping 6.5 mm screws for the bottom which I'll probably put in only after I've done everything else and tested the switches, in case I have to disassemble to troubleshoot. Once I'm happy it's all fine, I'll put those in, retest, and close it up. Just waiting for the hardware to arrive, then I need to steal a drill off my dad because I've somehow reached the age of 30 without needing or owning a drill, then I'll get to work properly.

[fohat]

without needing or owning a drill

Personally, I think that a Dremel is much easier and more accurate. Use both hands, put on your Dad's reading glasses and get in there very close.

Presumably you have read about being careful to preserve the alignment crescents on either side of the holes you will be drilling, and how to prepare the cut-off stumps of the rivets such as shaving them flat and dimpling them to keep the drill bit from walking.

[an_achronism]

Personally, I think that a Dremel is much easier and more accurate. Use both hands, put on your Dad's reading glasses and get in there very close.

Presumably you have read about being careful to preserve the alignment crescents on either side of the holes you will be drilling, and how to prepare the cut-off stumps of the rivets such as shaving them flat and dimpling them to keep the drill bit from walking.

I've honestly never used a Dremel but I didn't necessarily think they would be any more or less "accurate" as long as using right bit size etc. But yes, I've already made wee pilot dips to help guide the drill bit and I will be extremely careful to keep the alignment nubs so the backplate lines up properly and the bolts don't go through squint. Honestly the main issue with a Dremel is I've just spent all my money on Model Fs and Ms and others so I don't really have cash for a proper Dremel hahah.

[anthonymak]

swelling of the rubber mat causes premature actuation. replace the mat if possible if not, remove it.

[fohat]

replace the mat if possible

I don't recommend removing it, but I would surely recommend Unicomp's new thin white latex mats over the original thick black rubber ones.

Unfortunately that is much easier and cheaper for us in the US than for international customers.

[an_achronism]

If that's true though, then it is presumably possible that I'm right about it being caused by dirt under the flippers, right? As in, either way, it would decrease the amount of distance the flipper has to travel to cause a PCB activation.

In any case, I have cleaned and dried the mat carefully, but I can do anything much more until I have a drill/Dremel and the hardware. The hex nuts were out of stock so I'm going to have to wait a while. I'm impatient, hahah.

[an_achronism]

The hardware arrived earlier than expected but I still have a barrier to get past before I can do this. It's getting on my tits because I have about a dozen keyboard projects to do (and numerous unrelated and definitely more important tasks to spend time on) and the M is kind of lying in bits all over the place right now but the only thing that's really in the way now is lack of a drill/rotary tool.

I keep seeing that a Dremel or similar is the best bet, but I would have to buy one, and they appear to be expensive and not come with the right drill bit I'd need for a bolt mod. A drill, however, I can get for "free", though because of COVID probably have to pay to post it here. Would you reckon I should just use a drill or buy a Dremel or Dremel clone? If the latter, can anybody recommend one?

I have clipped down the plastic posts as neatly as I reckon is doable but don't have a rotary thing to actually *sand* them down with; I'm guessing that's not 100% necessary but would make it slightly easier.

[fohat]

a Dremel or similar is the best bet, but I would have to buy one, and they appear to be expensive and not come with the right drill bit

Cheap Chinese rotary tools on ebay are only about $15, but you would have to wait for delivery. They are invaluable for all manner of craft projects and household repairs.

I find that a 1/16" bit is perfect for an M2 screw - it is just slightly undersized and the screw makes a nice tight fit for itself.

[an_achronism]

a Dremel or similar is the best bet, but I would have to buy one, and they appear to be expensive and not come with the right drill bit

Cheap Chinese rotary tools on ebay are only about $15, but you would have to wait for delivery. They are invaluable for all manner of craft projects and household repairs.

I find that a 1/16" bit is perfect for an M2 screw - it is just slightly undersized and the screw makes a nice tight fit for itself.

That's the trouble, knowing where to look for a tool that has a 1/16" bit. I'm in the UK, and we don't use imperial measurements for things like that. Closest I know of is 2 mm but that actually *is* M2 afaik so wouldn't give the slightly-too-tight effect I want.

And there are loads of slightly dodgy looking knockoff Dremels on Amazon UK etc. but I dunno whether to trust any of 'em, honestly.

[fohat]

A knock-off is usually inferior, but does it matter? How many times will you use it in the next decade or 2 or 3?

I have 2 "Dremels", 1 made in the 1980s (Craftsman brand, single speed) and 1 made in the 1990s (Dremel brand, multiple speed). The Craftsman is more powerful and better in almost every way. Both are metal, undoubtedly anything you buy today will be plastic.

I use the multi-speed Dremel on the slowest setting and wish that there was a setting below "Low" ....

A 1.5mm bit would probably work fine but 1/16" is slightly over 1.5mm and probably slightly easier to work with.

[Polecat]

A knock-off is usually inferior, but does it matter? How many times will you use it in the next decade or 2 or 3?

I have 2 "Dremels", 1 made in the 1980s (Craftsman brand, single speed) and 1 made in the 1990s (Dremel brand, multiple speed). The Craftsman is more powerful and better in almost every way. Both are metal, undoubtedly anything you buy today will be plastic.

I use the multi-speed Dremel on the slowest setting and wish that there was a setting below "Low" ....

A 1.5mm bit would probably work fine but 1/16" is slightly over 1.5mm and probably slightly easier to work with.

I have one of those metal single speed Dremels. I use it with an ancient speed control box made for an electric drill or other brush-type motor power tool, zero to full speed, works like a champ!

[an_achronism]

Mission accomplished!







Keys no longer actuating early or sticking/repeating when they shouldn't. I suspect my theory that dirt on the rubber mat was causing that may have been correct. Missing caps added, cleaned and cleaned and cleaned again (ultimately resorted to dishwasher for the chassis but not the barrel plate in case it affected the inside of the barrels negatively), bolt modded to get it back together.

Things I learned:

1. Probably don't put bolts in the second-to-bottom row, which had been mentioned elsewhere (including in this thread) but I decided to take a chance on because the case on this particular M was too slack and I thought it might tighten it up. It has, but it's a tad bulgey. Feels more solid, but you can see the sides of the case bulging out a bit if you look closely.

2. If a spring and flipper assembly becomes misaligned, it will be a gigantic pain in the hole, so repeatedly test for this during the bolt modding process by tilting the board up and down to check all of the spring assemblies move up and down as they should. If any move at a funny diagonal angle instead of up and down, or if they just stay stuck pointing straight up, they're misaligned. Depending on how far in you notice this, it's possible that you might be able to fix it without a full disassembly: loosen some of the bolts in the surrounding area and then lift up the barrel plate gently (gently! don't crack the damn thing) then poke the flipper with tweezers or a toothpick or something to shove it out of the barrel plate (I found they sometimes get stuck a couple of mm out of position and wedge into the wrong bit of the barrel plate). You can then carefully lift the spring with tweezers and rotate it ever so slightly and pull it up into the correct slot in the barrel plate, which you'll be able to feel although you can't see it happening. Let go of the lifted plate and it'll pin it in place like the others. If it's badly misaligned, you might not get away with that, though. I got everything hunky dory on my first try except numpad 9 got stuck at a slight angle, but the tweezer trick worked.

3. It is incredibly finicky to get the first few bolts in but after that it's reasonably straightforward, just tedious. Screw modding would be easier, but is somewhat more risky to revert if you have to reopen the assembly again (e.g. to fix misaligned flippers).

[Muirium]

Nice job, brah, but you forgot about those Windows keys…

[an_achronism]

Nice job, brah, but you forgot about those Windows keys…

P.S. I'm selling this artisan keycap, PM. PayPal only, $80 ea.

[Muirium]

Aw man. That thing’s sweet! Love the artisan touch. Don’t you take dogecoin?

[an_achronism]

Tried flipping the bottom row of bolts around the opposite way so they're coming up through the assembly instead of pointing downwards toward the back. The head of a bolt is quite a bit shorter than an anti-vibration washer and hex nut, so it now fits in the case better, though I think the next row up is also causing some tightness so it still has a bit of pressure on it. I don't think it'll be as much of a problem though. Didn't want to leave it the way it was before, mostly in case it strained the case. I don't think this is going to be enough to cause an issue now.

[fohat]

the next row up is also causing some tightness

Dremel, burr tip.

[an_achronism]

Dremel, burr tip.

I'm not following. On what specifically?

[Muirium]

Cut the bolts excess threads off, I think. Make ‘em fit whether they like it or not!

[an_achronism]

Cut the bolts excess threads off, I think. Make ‘em fit whether they like it or not!

Ah, but there are no excess threads. The bolts don't extend beyond the hex nuts. So no. Hahaha.

[Muirium]

Fair enough. Is it still too tight? Maybe the case is next!

[an_achronism]

Fair enough. Is it still too tight? Maybe the case is next!

I'm sure I could just flip the next row of bolts around as well. If the bolts go bottom-to-top, then the bolt head is taking up less room underneath the assembly than the washer and nut otherwise would have if it were in the top-to-bottom orientation. But it's probably fine as is to be honest.

[fohat]

Dremel, burr tip.

On what specifically?

Sorry, numerous people have suggested scooping little craters out of the lower case shell. I have done it a time or 2, but generally M2x8 screws and nuts without washers have not caused problems for me.

I just realized that if you are replacing the original thick black rubber with the new thin white latex, you might have lost a millimeter or so and the effect is to "lengthen" the screw.

[an_achronism]

Sorry, numerous people have suggested scooping little craters out of the lower case shell. I have done it a time or 2, but generally M2x8 screws and nuts without washers have not caused problems for me.

Ah, I see. I'd rather not alter the case destructively, so I'll probably either flip another row of bolts or just call it fine as it is. I don't think it's likely to be an actual problem, it's just somewhat tight. As long as it's not properly bulging it's hopefully OK.

I just realized that if you are replacing the original thick black rubber with the new thin white latex, you might have lost a millimeter or so and the effect is to "lengthen" the screw.

I haven't, cleaning the original mat did the trick. It's not the length of the bolts causing the problem, it's the stacked thickness of the washer and hex nut. Flipped, the bolt head isn't as tall.

[fohat]

I'd rather not alter the case destructively

the stacked thickness of the washer and hex nut

Worrying about invisibly "altering" the case of a keyboard as common as a used mid-generation Model M "destructively" seems a bit fanatical to me. Possibly if it was a very very early specimen with the "bar code" label in pristine condition I might consider avoiding altering the bottom shell, but even then no one would ever know until they opened it.

But while I admit that I have a strong "collector gene" I try to be realistic about what is collectible and what is a tool to be optimized for actual use. If I put my keyboard collection up for sale, I would probably hear a lot of complaints about my modifications. You don't like an ANSI mod on a Model F "Unsaver"? Go jump in the lake.

The washer certainly needs to be left off when it creates interference on those lower rows.