So, this amazing big cog clock was created for a friend who has fascination with cogs and mechanical stuff. The design is based on his ideas with some ideas from other clocks he had seen – the final agreed ‘design concept’ was three rough circles drawn on piece of scrap paper. OK, agreed, a more detailed concept was needed to be able to take this forward.
Based on images etc, I developed what I thought would be a good idea. My friend liked it too and so the fun could begin!
The blanks from which the cogs were cut were formed from 12 segments of beech. The aim was to have a diameter of around 600mm for the main cog and around 450mm for the side cogs; the main cog was going to be around 35mm thick. A series of rough sized segments were cut so that they could be machined on the CNC to get as close to a 30 degree angle as possible.
So after a little while, I had 12 machined segments and the moment of truth had arrived, how accurate was the cutting and would the 12 segments go together snugly? Winner! 12 segments glued with some Titebond II and not an open joint in sight. The glued blanks were clamped and given a good 24 hours for the glue to dry / cure.
And so the CNC-ing could begin in earnest. Most of the milling was done with a 6mm down cut bit (bought from Rennie Tools – a great range, good prices and super service) with a depth of cut of 2mm running at around 27mm/second.
