A second source is insurance, and like any insurance it is worth buying only for risks that would actually hurt. The components that justify it are the ones that would stop production, have a long replacement lead time, and currently come from one place — usually a short list, and usually known to the people who maintain the machines.
7 min read · Last reviewed 28 September 2026 · All resources
Many organisations believe they are dependent on a supplier when they are actually dependent on that supplier's drawing. Without documentation, changing source means starting from a sample — under time pressure, at the worst moment.
Securing an approved drawing you own converts supplier dependency into a purchasing decision. That is frequently the highest-value step, and it can be taken without changing supplier at all.
A second source qualified only on paper is not a second source. It needs to have made the part, to your drawing, and to have had those parts inspected and ideally used.
That means placing a real order, which has a cost. It is the cost of the insurance, and a second source that has never produced the part is worth considerably less than the effort of arranging it suggested.
Second sourcing does not require concealment. Most suppliers understand why a customer dual-sources a critical item, and being open about it usually preserves the relationship better than being discovered.
It also lets your primary supplier respond — sometimes with better stock holding or lead times, which may address the original risk more cheaply.
A source qualified three years ago and not used since is an assumption, not a capability. Equipment changes, people leave, and the drawing may have moved on.
A periodic order — even a small one — keeps the route proven and the relationship current, which is what you are actually paying for.
FAQ
The questions engineers and buyers ask before sending a drawing. If yours is not here, ask it directly — you will get an engineer's answer, not a brochure.
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No. For parts that are readily available, or whose absence is merely inconvenient, stock or a good relationship with one supplier is usually cheaper and simpler.
Most will not for a genuinely critical item, particularly if you explain the reasoning. A supplier who objects strongly to any second source is itself worth noting.
You can, by having the part reverse engineered — but that is work best done calmly in advance rather than during an outage. Getting the drawing first is the better sequence.
Both work to the same approved drawing revision, and both parts are inspected against it. Where a characteristic is not on the drawing, the two will eventually differ.
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