... chair is close to being symmetrical, but a "L1" bridge chair is a long way off. With square-on timbering only half the chairs are skewed, but some of them significantly. With equalized timbering, the skewing is less but some skewing applies to nearly all of the chairs. To illustrate that, here I have intentionally exaggerated the lack of symmetry. You can see that the gauge-face intersection with the centre-line of the chair does not coincide with the centre-line of the timber: 2_180233_350000000.png I know it is only a small difference, but the human brain being what is, even a small offset from being central within the timber width is very noticeable. And in most prototype cases, wrong. However, as you can see, I think I have got it working. regards, Martin. posted: 20 Jan 2016 23:42 from: Martin Wynne Hi Andy, Another progress report. 2_201814_250000000.png 2_201814_490000000.png A few notes about this. Initially this is going to be restricted to the REA bullhead designs for ...