So my 2 cents since I suggested the overview...by no means all encapsulating and certainly untested. I would normally write these out on a sheet of paper, draw lines for the relationships, pencil in the field data types and think about whether or not it supports my goals. You certainly could embellish this but given that it's kind of a hobby and not a corporate thing as I first thought, I tried to balance simplicity with function. In case it's not known, PK is primary key (I'd use autonumber field) and FK is the foreign key value, which of course is the PK from the parent table. I might even leave out the equipment table since this isn't about corporate or personally owned assets. Again, not vetted....
tblCustomer
CustPk - autonumber PK
FName
LName
Phone
etc - attributes of the customer only
tblEquipment
EquipIdPk
EquipType
Make
Model
Serial
etc
tblJobs
JobIdPK
CustIDFk
EquipmentIdFk
Notes (operating complaint or customer service request)
tblParts
PartIdPK
JobIdFk
Qty
PartNum
Description
Cost
Price
tblJobLabour
LabourIdPk
JobIdFk
LbrHours
LbrRate
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.