Adding a Second Source for Machined Parts
China plus one is a strategy that sounds like a decision and is really a project. The decision takes an afternoon. The project takes two quarters, and most of it is unglamorous: choosing the right part, running two sources in parallel long enough to trust the new one and resisting the urge to move everything at once.
Here is the sequence that keeps the existing supply running while a second source becomes real.
Why the second source is usually not about price
Buyers who move because the quote is lower tend to move back. The reasons that stick are structural:
- Tariff and origin exposure. A change in duty rates or origin rules can break landed cost overnight, and it applies to a country, not to a supplier.
- Concentration risk. One supplier, one region, one port. A shutdown anywhere in that chain stops your line.
- Capacity that is not yours. When your supplier’s biggest customer takes a large order, your delivery date is the one that moves.
- Leverage. A supplier that knows it is the only source prices accordingly at renewal.
Write down which of these applies to you before you start. It decides which part you move and what “success” means at the end.
Pick the part that teaches you the most and hurts the least
The instinct is to move the highest spend part first, because the saving looks biggest. That is the part that should move last.
Good first candidate:
- Stable drawing, no revision planned
- Repeating quantity, so the new shop runs it more than once
- Common material, bought locally at both sources
- Real but survivable volume, with a few weeks of stock behind it
- Tolerances that are honest rather than copied from a template
Bad first candidate: a new design under a launch deadline, a single prototype, a part with a certification attached to the current supplier or the part that keeps your biggest customer running.
You are buying information with this order. Pay a fair price for it.
Run both, do not switch
The mistake that turns a sourcing project into a firefight is treating the second source as a replacement before it has proved anything. The sequence that works:
- Quote in parallel. Same drawing revision, same quantity, same shipping term, same document list. Without that, you are not comparing.
- First article from the new source while the existing source keeps shipping. Review it properly. A first article inspection is the cheapest insurance in this whole process.
- A real batch, not a sample run. The owner watches a sample. Production is what you are buying.
- Two or three consecutive deliveries. Consistency is the thing you are testing, and it only shows up over repeats.
- Then split the volume and keep it split.
Through all of that, the existing supplier keeps its share. You are adding capacity, not staging an exit.
What to measure, on both sides
Keep the scorecard short enough that you actually fill it in.
| Measure | How to record it |
|---|---|
| Landed cost per part | Not unit price. See the landed cost method |
| On time delivery | Against the date confirmed on the purchase order, not the date you hoped for |
| First pass yield | Parts accepted without rework or concession, as a percentage |
| Response time | Hours to a technical answer, tracked for a month |
| Change handling | What happened the first time you revised the drawing |
Run it for both sources over the same period. The numbers usually surprise people in both directions.
Where Vietnam fits, honestly
Vietnam is one of several plus one destinations, and it is not automatically the right one for your part. It tends to fit when:
- The material is a common grade that local stockists hold
- The quantity is a batch rather than a prototype or a very high volume automated run
- You can plan lead time in weeks rather than days
- Nothing about the part is export controlled
It tends not to fit when the part needs an exotic alloy, a specialised secondary process with a thin local supply base or a certification regime that takes years to build. Those are the cases where the honest answer is to look elsewhere, and a supplier that tells you so is doing you a favour. The self check on the home page runs through this in six questions.
The mistakes that cost the most
Moving everything at once. You lose the reference point that tells you whether the new source is good.
Comparing an EXW quote to a DAP quote. Different numbers, different scope. Fix the Incoterm before you compare anything.
Skipping the origin question. A second source in a different country changes your duty position and your paperwork. Sort out the certificate of origin before the first shipment, not after it has sailed.
Treating the new shop as a supplier from day one. For the first three orders it is a candidate. Inspect like it.
If you have a part that fits the profile above, send the drawing and we will pass it to up to three machine shops in Vietnam that already run that material and quantity. You compare their quotes against your current source yourself.
Frequently asked questions
Should I tell my current supplier I am dual sourcing?
Usually yes, once the second source has passed a first article. Suppliers find out anyway, and finding out from a competitor is worse than hearing it from you. Framing it as capacity insurance rather than a price play keeps the relationship intact.
How much volume should the second source get?
Enough that the line stays warm and the price stays honest, which in practice means a repeating share rather than an occasional order. A source that runs your part twice a year has forgotten it by the third time. Set the split on how much disruption you could absorb, not on a target percentage.
Does dual sourcing always cost more?
Per piece, often yes, because you split volume across two setups and two tooling sets. Against a stockout, a tariff change or a supplier walking away from a low margin part, it is usually cheaper. Price it as insurance, not as procurement.
Need a quote for a part like this?
Send the drawing. We shortlist up to 3 machine shops in Vietnam, manage the order if you want us to and reply within 24 business hours.
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