Single sourcing
Buying a part from one supplier by choice, even though others could make it. Not the same as sole sourcing, where only one supplier can.
Also called: Mono-sourcing, Single-source supply
Single sourcing is a decision. Several suppliers could make the part, and you pick one. Usually for good reasons: the volume is too small to split, the tool costs €80,000 and you only want to pay for one, or the supplier has earned it on quality.
The word gets confused with sole sourcing, which is a constraint rather than a choice. If only one company in the world holds the patent, or the drawing names a single manufacturer’s part number, you are sole-sourced whether you like it or not.
The risk
The risk of single sourcing is not the supplier going bankrupt, though that happens. It is the slow drift. With no alternative quoted in years, the price follows the supplier’s increases, and the knowledge of how the part is really made sits on their side of the fence.
A common pattern: 60 to 70% of a manufacturer’s direct references are single-sourced, and most of those were never decided as such. Someone nominated a supplier for a prototype in 2014, and nobody reopened it.
Managing it
Splitting every part between two suppliers is rarely worth it. What works better is knowing, for each single-sourced part, whether a second source could exist: who else has the process, the capacity and the tonnage, and what a switch would cost. That turns a dependency into an option, which is what you need at the next price review.