How to create a Pie Chart using the same column but varying filters?

I want to create a simple pie chart that COUNTS (PART NUMBER) and the legend will show category by Mechanical, Hydraulic, and Electrical.

Problem is when I add "COUNTOF PART NUMBER" field to the "Values" and add "Department" to "Filters on this visual" I can only pick one item. Like I need to add "COUNTOF PART NUMBER" field to the "Values" 3 times, and have each repetitive count filter differnetly (i.e., Mechanical, electrical, hydraulic).

I've been running in circles for hours trying to create an entirely new table or new calcualted colum/field, but I just can't figure this out. Please help!