Cost of Internal Jobs

In our company, we have established product groups such as "Internal-
Machining" or "Internal-Composities", to capture the costs of doing
internal jobs. Currently, all "Sales", "WIP", and "COS" (Labor,
burden, etc.)for the chosen product group are directed to one
manufacturing overhead account, such as 02-6800-01 for "Internal-
Machining" or 02-6800-06 for "Internal-Composites", that hits the
department in which the bulk of the labor is performed.

The problems comes in when one department is performing work for
another department and the overhead expense is charged to the
department doing the work rather than the depart for which the work
is done. Also, we are not sure how burden costs should be handled.

Any ideas are welcome. Thanks.