XT key sizes

[y11971alex]

I was trying to make an 83-key XT keyboard layout diagram on http://www.keyboard-layout-editor.com/ late last evening, but I came across several problems when I was trying to align the backspace key.

1. If a normal alphanumeric block was 15 keys long, then backspace needs to be 2 keys long, since the top row has only 14 keys.
2. The second row has tab (3/2) and a slightly enlarged right bracket (5/4?), but they need to line up with the third row to make room for the return key, which is 2 keys tall and 1 key long (since it aligns with the PrtSc key), meaning that Ctrl needs to be 7/4 keys, instead of 2 full keys long.
3. If the alphanumeric block is 15 keys on the XT, then the right bracket needs to be 3/2 instead of 5/4, since the size of tab is fixed by the offset of Q. 
4.This means that the alphanumeric block is only 14 and 3/4 keys long on the XT, and the backspace is only 7/4 long, not 2.
5. But I don't seem to find a measurable difference on the actual backspace key and the 0/insert key, which I know for sure is 2 keys long.

 

[E TwentyNine]

Backspace is the same width as Ctrl, 7/4 sounds about right.

Caps Lock, 0/Ins, ./Del, Num Lock and Scroll Lock are all two keys wide.

[khirin]

Using my vernier caliper, the back space key is 32.5mm and the 0/insert key is 37mm while a normal key is 18mm.

Says the space between any two keys is 1mm, the 0/insert (and also the alt, the three lock keys) is about 2 keys long (18+18+1 = 37). 

Therefore, the back space (and also the ctrl key)  should be 32.5/37 ~  1.75  or 7/4 key 

[fohat.digs]

Perhaps I am misunderstanding the purpose of the question, but the operative driver is the location of the barrels (aka chimneys) underneath.

If you can't get caps with properly located stems relative to whatever barrel locations are already fixed, what does it matter exactly how big the caps are?

[y11971alex]

Perhaps I am misunderstanding the purpose of the question, but the operative driver is the location of the barrels (aka chimneys) underneath.

If you can't get caps with properly located stems relative to whatever barrel locations are already fixed, what does it matter exactly how big the caps are?

I'm just trying the draw a diagram for the XT keyboard, since a photo (of the XT) is usually too large to post as an image in some fora.