The solution provided a design challenge in that ten highly accurate drill holes, of just 1.52 mm in diameter, on the ballscrew nuts were needed. The problem is that metal expands and contracts during the hardening process, resulting in slight changes in position and size of the all-important holes. These changes are very difficult to predict, but, after successive cycles of measuring and vacuum hardening to 59-63 HRC, Eichenberger’s developers succeeded in adjusting the drill holes to the required size and with an impressive tolerance of just ± 0.015mm.
While the mechanism proves to operate more accurately and smoothly, it is unlikely to be applied to aircraft seats more widely due to its complex nature and higher costs.