IBM Model F XT vs AT key stem smoothness

[milk_stain]

After thoroughly enjoying the Model F AT I've had for a few years, I decided I'd get my hands on the XT model. Oddly enough, the key-feel was a little worse than the AT, and after taking off a keycap, I noticed the stems of the XT were rough in texture compared to the smooth AT stems, as shown here: https://imgur.com/a/BkUdwgc. This was apparent in all of the keys on the keyboard, even uncommonly used ones such as the Function keys.

This leads to a noticeable roughness when pressing the key slightly off center (not unlike scratchy cherry reds), though pressing dead center makes the roughness not noticeable. The AT keycaps do not feel scratchy at all even when pressed off-center, and this makes it feel quite a bit better than the XT that I have.

Can anyone confirm if the roughness is an inherent feature of XT keycaps compared to AT? Or is this simply differences in year/factory/amount of use? I also have a 1986 silver badge Model M and an IBM Wheelwriter with the same scratchy texture on the keycap stems, and similar scratchy keyfeel, but it does seem odd that the XT would be scratchier than the later AT...

[ddrfraser1]

Interesting. I wonder how this compares to other Ms and Fs.

[SneakyRobb]

Hi I wonder if these are keycaps from UK vs USA manufacture. Are you able to see if it says that on the back labels of the keyboards?

In general I've personally found IBM, sort of like ALPS, to often have slight variations across otherwise interchangeable parts. Often without any explanation. There are slightly different Model F capacitive flippers for instance with different shapes. If I recall correctly some users have even found the different shapes in the same single keyboard without any clear reason why that would be the case. I wonder if this is one of those situations.

Regardless neat and good of you to notice!

[milk_stain]

I uploaded pictures of the stickers here: https://imgur.com/a/03vkyL1

There's no obvious indication as to whether they're USA or UK, unless someone knows what the codes mean.

Kind of a shame my XT is on the scratchy side. It's still a great feeling keyboard, but knowing the smoothness of my AT exists ruins the experience somewhat.

[Fkazim]

I uploaded pictures of the stickers here: https://imgur.com/a/03vkyL1

There's no obvious indication as to whether they're USA or UK, unless someone knows what the codes mean.

Kind of a shame my XT is on the scratchy side. It's still a great feeling keyboard, but knowing the smoothness of my AT exists ruins the experience somewhat.

Both those Model F's are the US made ones. As all UK Model F's have a clear date of manufacture and also say Made In United Kingdom on the keyboards back label. Below is an image of the label on My UK IBM Model F XT. My UK made AT also has a similar style label as my XT.

Below is an image of the lablel on my XT

My IBM XT.jpg (120.91 KiB) Viewed 2569 times

[milk_stain]

Interesting..... I want to rule out wear being the issue since the tops of the XT caps are still nicely textured and in good condition. My wheelwriter on the other hand is pretty worn and the key tops are quite smooth now, but still has the rough stems.

I wonder if anyone else with an XT and AT (or other Models F) could comment on the stem smoothness, maybe we could find a pattern to this...

[daedalus]

Keep in mind as well that the XT and AT systems were produced in parallel between 1984 and 1987, and that PC/XT systems were produced in far more numbers (i.e. an order of magnitude more) than the AT systems. So I would expect that AT keyboards would have a similar build quality compared with the XT keyboards of the same vintage.

[milk_stain]

Interesting, if not US/UK differences, maybe it's a difference between US plants, or years in those plants (older Keycap molds getting less smooth over time?)

To make matters more complicated, I got a hold of another XT sample. This time the keycap stems were smooth like my AT and the legends were slightly thicker and fuzzier (like my AT) than the thin ones of the first XT.

The back plate of the second XT also had a similar sticker to my AT, which makes me think they were made in the same plant.

Here are pics of the second XT backplate and the two XT Keycaps side by side (left is thick legend smooth, right is thin legend rough). https://photos.app.goo.gl/iR7WH1Sa126XT18r8

I wonder if this means thick fuzzy legends = smoother keys. After all, my scratchy model M has thin, crisp legends. The mystery continues...