Guides / Choosing a Supplier

Second Sourcing a Critical Machined Part Without Doubling the Work

September 24, 2026

Second sourcing is easy to agree in principle and easy to postpone forever, because the first source is working. The question is not whether redundancy is good. It is which parts deserve the cost of a second qualification.

Which parts earn a second source

Rank your machined parts against three questions, and the list shortens fast.

1. What happens on the day it is late? A part that stops a line scores differently from one that sits in a drawer.
2. How long is the replacement path? A plate with a frozen drawing can be requoted in a week. A qualified chamber part with an outside finisher cannot.
3. How concentrated is the supply? If one shop, one finisher or one material supplier appears behind several of your parts, that is a single point of failure wearing three names.

The parts that score high on all three are usually a small group: a handful of jigs and change parts that gate production, plus anything with a long qualification behind it.

What a second source actually costs

• One extra qualification: first article, pilot lot, the review of both
• A split that raises unit price a little at each shop
• Engineering time to keep two sets of process notes current
• The discipline to keep both drawings identical, which is where most programmes quietly fail

Against that, the alternative cost is the day the line waits. Most buyers never calculate that number, which is why the conversation stalls.

Transfer the process, not just the drawing

A second source that receives only a STEP file and a PDF rediscovers every lesson the first shop already paid for. What should travel with the package:

• The ballooned drawing and the accepted first article report, so the new shop sees what was measured and how
• The process sequence that matters, for example weld then finish machine, or stress relieve before finishing
• The finish specification with masking, and which finisher the first shop uses if that is not exclusive
• The packing level and any handling restriction
• The list of concessions previously granted, so the new shop knows where the real tolerance sits

This is also the argument for writing that package properly the first time. The RFQ template and the drawing release checklist exist so a transfer is a copy rather than an archaeology project.

Keep them honest without playing them off

The failure mode of dual sourcing is a buyer who uses each quote to beat the other down. It works twice, then both shops start pricing defensively and your urgent work goes to the back of both queues.

What works better is a stated split, reviewed on delivery performance and quality rather than on price alone, with the rule written down. Shops respond to predictability, because it lets them plan capacity and a shop that can plan for you quotes better than one that cannot.

A realistic sequence

1. Pick one part that gates production and has a frozen drawing
2. Qualify the second shop on that part alone, with a paid pilot lot at the real quantity
3. Measure delivery, not only dimensions
4. Move a stated share of the volume, permanently
5. Use the same package for the next part rather than starting again

If you want a second source qualified against the same criteria as the first, send the RFQ and say it is a second source. We will match shops that are genuinely independent of the first one rather than the same finisher wearing a different name.

Frequently asked questions

More on choosing a supplier

• What an NDA Should Cover When Drawings Cross Borders
• Vietnam, Taiwan or Malaysia for Machined Semiconductor Parts
• What to Put in an RFQ so the Quotes Are Comparable
• Sourcing Semiconductor Parts in Vietnam: What to Check Before You Send a Drawing

All guides and the sourcing glossary.