We have tools sharpened and this is how we do it -
Create a part number for the service - we use "RESHARPEN" as the part#, "N" as the part type and a class that applies to our expense account "EXP"
Then we enter a PO for RESHARPEN with a single line item price for the entire lot - 25 parts @ $100 lot charge
 
Line 1  - RESHARPEN - qty 25  price 100 lot
second line description - misc shop tools
 
If there are parts that I need to track - like when we get things calibrated - we created a part number called CALIBRATION and I put each parts Serial Number and description in the description lines of the PO, so that I have a record of what went out and our Reciever can be sure that we get all the parts back.
Hope that helps
Debra