Thanks for all the input.
Nylacast link useful for the mechanical data. I have an old trade article on design of polymer gears so will pop the numbers in. Similar tensile but Oilon about half the impact and compressive strength of Tufnol. But other than noise assume that still useful to have a mechanical "fuse" in the system and not a problem if I make some spares.
Direct Plastics was were I was looking
45mm dia x 500 @£12.55 going to yield about 22 slices, where as 200×300 x 20 Tufnol @ £43
I have got a small scrap of Tufnol which squeezed one blank of each 30T and 25T will but will a couple of teeth the tips will be missing, but even if I just use the Oilon to prove the rack cutter, which my preferred gear cutting method.
Thanks