
first thumb - a basic chunk of 4140 steel with a new ring gear
not that interesting but it what I start with

again not that interesting but again the start of the machining

this thumb is starting to look like a flywheel - with the counter bore for the crank mounting
and the ring gear mounts machined ready to turn around and machine the front face

front face machined with the face counter bored and tapered for the bolt heads
the outside dia is also finished - time to turn it to the back again

material is carved out of the back to reduce weight - I weighed it at this stage and it went
4.75 Kg ( 10 1/2 pound ) of cause there is another 1 Kg in the ring gear ( 2.2 pound ) still to be fitted

next part of the job is on the mill - so as you can see I run a cutter from the outside edge to where the fiction plate surface finishes these 12 cuts remove about .7 Kg ( 1 1/2 pound )
from the out side edge

the last jobs to do are drill and tap to bolt up the presure plate with of cause the dowels
fit the ring gear and have it balanced
I'll post pics of the finish item soon