... S4 has supposedly prototypical clearances, and even there people seem to use the 30mm tool. My personal approach is to use the triangular tool and use the C&L gauges when I know I want a particular widening in pointwork. 3591_071503_160000000.png The blue line in the graph shows what the 30mm tool does. It gives nowhere near the prototypical widening at 4'9", but can be used down to a radius of less than 500mm before it's giving too much widening. Below is a spreadsheet that gives the same information as the graph 3591_071503_500000000.png 3591_071509_260000000.png Hopefully Martin will correct anything he considers erroneous. Attachment: attach_3172_3809_snip_GW.JPG 93 Last edited on 7 Nov 2020 20:17 by Julian Roberts posted: 7 Nov 2020 23:49 from: Rob Manchester Hi Julian, Thanks again for your post. I quite like 3 point gauges as you can put a weight on the top of each which keeps them stable when laying track but I agree that it makes sense to have a 'maximum' value for widening and revert to the type in your last photo once the maximum value ...