Welcome to ModelEngineMaker !If you have problems registering or logging in, please use the contact menu option to request assistance.
Hi JimThe two countersink screws should be drilled for clearance for #4-40, and the hole showing between them should be drilled and tapped for #6-32 thread.Don't drill the hole between them through into the groove either - it should be a blind hole. Basically, looking at the base, all the blind holes from the top must be threaded for #3-48, the three blind holes from the bottom must be threaded #6-32, and all the through-holes should be drilled at clearance size for #4-40.M3 metric screws are a great replacement for the #4-40 American threads on most parts of Elmer's engines. If you do use different fasteners than the American ones specified, make a note on your plans to that effect next to mating parts - so that you can keep track of which holes must be what sizes.Kind regards, Arnold
Yes it is the crank pin. I would look to go up to 5mm rather than down to 4mm. If you are worried about the amount of metal left either side of the pin you could reduce the diameter of the curve on the top and bottom (hand file rather than turn).Jo