Model M scratchy keys

[timbetty]

Hello everybody,
I got myself a new IBM Model M 51G8572 from '97, which was never used.
The originial packaging had some scratches but was never even opened.
Some of the keys feel slightly scratchy ('k', ' ' ', 'End'), do they need some time to break in?
I don't want to rush into lubeing them with ptfe spray if it isn't absolutely necessary...

The springs are seated correctly and no rivets are broken.
I have not much experience, I only have had a Unicomp Model M for some time which I bold moded some weeks ago.

So, has someone experienced this before?

[Kurk]

Hard to judge from a distance. If I press some keys on some Model Ms here very slowly I can feel plastic sliding against plastic. Not really scratchy I would say. On the other hand, I have never used a new-in-box Model M so it may indeed need some time to break in.

[quantalume]

Welcome to the community! I have seen this occasionally. It usually happens with Unicomp key stems, however. I would suggest swapping key stems between a scratchy and non-scratchy position. This way you can determine if it is the stem or barrel that is at fault. Maybe a little light filing of the stem or barrel is in order. I have a lot of extra stems on hand and would be happy to send you a few if that is what it turns out to be.

[Hypersphere]

I have a Model M with the same model number and year. Mine was made by IBM in Scotland, and it is one of the smoothest Model M keyboards in my collection. There were some 51G8572 models that were made by Lexmark, but I do not have one of these for comparison. Is yours from Lexmark or from IBM in Scotland?

In general, I find that my IBM Model F XT keyboards feel smoother than my Model M boards. I have never tried lubing anything on an IBM board except the stabilizer wire on one of my XTs, and I am not sure if this was really necessary or if it made any difference in the feel or sound of the keyboard.

[timbetty]

Welcome to the community! I have seen this occasionally. It usually happens with Unicomp key stems, however. I would suggest swapping key stems between a scratchy and non-scratchy position. This way you can determine if it is the stem or barrel that is at fault. Maybe a little light filing of the stem or barrel is in order.

First of all, thank you. I don't feel really new to the community since I'm lurking since 2011 and registered a couple of month ago. So I wasn't really expecting a welcome after all that time.

I swaped the '1' and the '.' key from the number pad, the '1' was very scratchy and the '.' felt normal, but after the swap both feel a little scratchy, but the '1' key feels better, but still not fine, so it is probably the sum of the barrel and the stem?
What do you mean by filing?

The keyboard was made in Scotland by IBM and over all it is a extremely nice keyboard.

[quantalume]

I swaped the '1' and the '.' key from the number pad, the '1' was very scratchy and the '.' felt normal, but after the swap both feel a little scratchy, but the '1' key feels better, but still not fine, so it is probably the sum of the barrel and the stem?
What do you mean by filing?

I mean use a fine file or piece of sandpaper to take a small amount of material, on the order of 0.1mm, from the areas producing the friction, likely the retention "ears" illustrated below.


Edit: After splitting apart another Model M today, I took a look at the inside of the barrels, and it is definitely not the retention ears that would be causing the friction. They only contact the barrel plate at the very top end of their travel. It is most likely some other part of the stem rubbing.

It's possible the surfaces responsible for the friction will wear away over time, so another option is to just wait and see.

[timbetty]

I swaped the '1' and the '.' key from the number pad, the '1' was very scratchy and the '.' felt normal, but after the swap both feel a little scratchy, but the '1' key feels better, but still not fine, so it is probably the sum of the barrel and the stem?
What do you mean by filing?

I mean use a fine file or piece of sandpaper to take a small amount of material, on the order of 0.1mm, from the areas producing the friction, likely the retention "ears" illustrated below.

stem.jpg

It's possible the surfaces responsible for the friction will wear away over time, so another option is to just wait and see.

Thanks very much.
Since I'm currently writing my thesis on that keyboard, which involves a lot of programming and writing, I think I will waite a month.
If those keys are still scratchy by that time I will try the method you proposed.

[M'er Forever]

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