I mentioned in the T400s sneak peek video that we had tightened up the tolerances between the keys to improve the overall system appearance and reduce the likelyhood of crumbs, or other debris, from slipping into the keyboard scissor mechanisms. We did not do this at the expense of changing the key pitch or altering the contoured portion of the key that you feel. It was of paramount importance that we did not change the typing feel with this enhancement. What we did was to increase the size of the skirt at the base of the key in order to make the gaps between the keys tighter. We also made the corner radii smaller for the same reason. The skirt is a technical term for the sidewall of the key that flares out towards the bottom of the key. The name makes a lot of sense when you think about the key cap shape. The previous ThinkPad keyboards had a nominal key gap dimension of .7mm. The T400s has a nominal gap of .4mm. A difference of .3mm may not sound like much but it makes a big difference.
Before moving forward with this change our Yamato engineering team did an extensive tolerance analysis and accelerated wear test to ensure we were on track with the change. We wanted to make certain the keys did not rub each other out of the box, or over time as the keyboard wears in. Yes, all keyboards wear in over time. People usually don't notice it since it happens so gradually. You can immediately see the overall visual impression that the tighter gaps make. Small design changes can have a big impact to the user experience. You won't feel this one, but you will be able to see it, and hopefully be less bothered by stray crumbs. Now back to eating my lunch while typing on my ThinkPad.