Q: How should we classify spare parts suppliers and vendors
A: My suggestion is that you classify suppliers/vendors of spare parts on a combination of spare part criticality and vendor exclusivity. So, if you have a critical spare part from a vendor that is the sole supplier of that part then they will be a critical supplier and you need to nurture that relationship (or find another supplier). At the other end of the scale, if you have a non-critical part from a vendor but where the part can be supplied by many vendors then they will not be a critical supplier. In this case you can reasonably ‘shop around’ for better pricing and delivery.
If you draw this up as a 2×2 matrix you will see that there are four possibilities.