Hi Clive
Yes, one wrong number in the calculations and the pitch spacing was wrong. An MDF prototype would have been a good idea. By the way I can’t open the pictures on my phone as it needs an app or something.
I ‘invested’ time writing a spreadsheet that works out the key geometry for any HTD 5 gear size you want. Watch me never need it again !

Hi pratt77
Thanks. Sounds interesting. Remember you don’t need anything as ambitious as my machine to make small parts. Whatever you build just leave yourself plenty of time as these projects eat up the months !