deskthority

While refurbishing the XT I have, I have started looking at later Model F boards. The XT uses very uncommon, center-stem stepped keys that are no longer manufactured, and a single barrel & pad per key, so it's not customizable... The later ones however seem much more flexible.

The problem remains that I have no idea how the backside of multi-wide keys sold at Unicomp "looks". As in, when splitting up larger keys, which combinations would fit and which wouldn't? Where is the stem on a 1.5u key, how can you split up a RShift, etc.? Is there some kind of online resource for this?

For keys that are 1.5u or less, the stem is centered. For 1.75u, it's centered on the left 1.5u part, with the extra step to the right (i.e., it is like a 1.5u key, and then an extra space of 0.25u). Any 2u has stems as though it were two separate 1u keys. The 2.25u left shift has stems as though it were a 1.25u and 1u key, and 2.75u right shift as though it were a 1u key and a 1.75u stepped key (as described above).

wcass can correct me - but :

1x BS keys are the only one that are center stemmed (.75" wide)
1.3x stem is offset by .0125" to the left (.9375" width)
1.5x stem is offset by .025" to the left (1.125" width)
2x is built of two 1x keys (1.5" width)
1.75x has the same stem position as 1.5x, with the extra width of the key to the right (1.3125" width)
2.25x Enter key has a 1x stem on the left, 1.3x stem on the right (1.6875" width)
2.25x Left Shift is inverted from the Enter key, 1.3x stem on the left, 1x stem on the right (1.6875" width)
2.75x Right Shift has a 1x stem on the left and 1.75x stem on the right (2.0625" width)
2x vertical Enter is just two 1x barrels in vertical config
2.75x Code key has a 1.5x stem on the left, then a 1x stem directly to its left, with some extra width to the right (2.0625" width)
ISO Enter is a 1.5x key on top and a 1.3x key underneath, right justified.

(Actually looking at my data, I need to re-check the right stem position for the 2.25x Enter key - it appears a couple thousandths off.)

Em... I'm a bit confused about 1.3. The math isn't working out... I always thought that was 1.25u... Or does IBM / Unicomp call them 1.3?

It can't really be 1.3, can it? The bottom of the ISO Enter is 1 key thinner than the ANSI Enter, which would be 2.25-1=1.25...

Unicomp calls them 1.3, everyone else calls them 1.25x.

It's a Bluegrass Country thing…

Forgot the spacebars...

7x Spacebar - first stem is 1x position on the left side of the bar, the other stem is centered 2.625" (5.25" width)
5.75x Spacebar - first stem is 1x position on the left side of the bar, the other stem is 2.25" to its right, center to center (4.3125" width)

Does someone know if Model M (Unicomp) 1.5u keys will fit on the Alt stem of a Model F AT? Looking at pics, it seems the stem of the Alt keys is offset to the RIGHT instead of the left...

Yes, they will fit just fine.

Yup. I've used them myself. And here's Snoopy's infamous black Kishsaver, using a set of Model M caps:



Don't rely on photos of Model Fs to guesstimate this sort of thing from where the case lines up. The whole mechanism can be adjusted from side to side inside the case, and is often off-centre when shot.