EMC tuning question.

I have a question about the relationship between DEFAULT_VELOCITY,
MAX_VELOCITY, DEFAULT_ACCELERATION and MAX_ACCELEATION. My system is
currently configured as follows:

DEFAULT_VELOCITY = 0.0167
MAX_VELOCITY = 0.2000
DEFAULT_ACCELERATON = 5.0
MAX_ACCELERATION = 5.0

On my Sherline 5400 mill with 20tpi lead screws this gives me reliable
rapids of 12ipm. I can increase MAX_VELOCITY up to 0.3000 which should give
me about 18ipm. This seems to require changes to he ACCELERATION parameters
but I can't come up with the appropriate numbers to get reliable operation.
What is the proper relation for the ACCELERATION parameters to the
MAX_VELOCITY parameter?

Thanks

John Guenther
'Ye Olde Pen Maker'
Sterling, Virginia