Switching Machine Shops Without a Production Gap Starts With a Parallel Run
Keep the outgoing shop running until the new shop has passed a first article and a short parallel run on live orders. Move work only when written cutover criteria are met, so a failed trial costs a delay on one part number instead of a stoppage.
A staged switch takes more attention up front and far less risk than a hard cutover. This guide covers the transfer package, the pilot parts, the parallel run, and the cutover rules, and it assumes the decision to move has been made. The steps hold whether the new shop offers broad precision CNC machining services or a single specialty process.
Choosing the new shop is a separate job, covered in our guide to evaluating a precision machine shop before you source. If no candidate exists yet, companies can contact a local MEP Center to start NIST’s supplier scouting program, which searches for domestic manufacturers nationwide. NIST puts typical turnaround at 30 to 45 days, so scouting suits a planned move, not an urgent one.
What belongs in the transfer package?
The new shop can only match what it can see. A complete package keeps the quote and the first lot from resting on guesses. The table lists what to gather and why each item matters.
| Item | Why it matters | What to send |
|---|---|---|
| Drawing at the current revision | The new shop cuts to the print it receives, and revision levels drift between shops | Released print with revision level, plus any open engineering changes |
| Specifications and callouts | Material, finish, and process notes decide purchasing and routing | Full note block, referenced specifications, and any approved substitutions |
| Outgoing shop’s inspection data | Gives the new shop a baseline for how each feature measured | Recent inspection reports, gaging details, and any special measurement methods |
| Fixture and tooling status | Decides whether setups must be rebuilt from scratch | List of fixtures, gages, and special tooling, with who owns each |
| Order schedule and forecast | Sets what must keep flowing while the move happens | Open orders, release dates, and expected quantities |
Missing or outdated drawings can stall a transfer before it starts. When the print no longer matches the part in service, the part itself becomes the source document, and reverse engineering can rebuild a usable drawing from it before any quote is issued.
Which part numbers should move first?
Start with parts that carry the least risk and teach the most. A good pilot shares its material and operations with other parts in the same family, so a clean result on one predicts how the rest will go. A part with a long, clean inspection history at the outgoing shop is also useful, because it gives you a baseline to compare against.
Avoid starting with the part that has a single source and no safety stock. If the trial goes badly, that part has no fallback. Pick one or two pilot part numbers, not a whole product line, and leave the critical ones until the first results are in.
A first article on transfer proves the new shop before volume does
Treat the first lot as a new program, even when the part has run for years elsewhere. First article inspection checks the new shop’s parts against every dimension and note on the print, and the outgoing shop’s inspection data shows how the same features measured before.
Where the two disagree, settle it before releasing more work. Differences in how the part is held, which features serve as datums, or how a feature is measured can each make a good part look bad, or the reverse. Resolving the disagreement at this stage costs a conversation. Resolving it after volume has moved costs far more.
How do you run both shops at once?
The outgoing shop keeps its open orders and current releases. The new shop takes the pilot part numbers on fresh orders. New releases then shift to the new shop in stages, one part family at a time, as each family clears the cutover criteria. One person on the buying side owns the order schedule for both shops, so nothing is released twice or dropped between them.
Agree the cutover rules in writing before the first order moves, so the decision does not depend on how anyone feels about the trial. These criteria work for most part families:
- The first article is accepted with no open dimensional issues
- Delivered lots match the print on every critical feature
- Pilot orders ship on the agreed schedule
- Documentation arrives in the format your receiving process needs
- Your team has a named contact at the new shop for changes and questions
If any criterion fails, the part stays with the outgoing shop while the cause is fixed. That is the value of the parallel run: a failed criterion becomes a note in the file, not a missed shipment.
How long should the parallel run last?
There is no fixed length. The run ends when the cutover criteria have been met across more than one lot, and not before. Parts with tighter tolerances, harder materials, or more lot-to-lot variation need more lots to show a pattern, while a simple part with a stable process may clear in fewer. Set the number of lots in the cutover rules instead of deciding case by case, and extend the run for any part family that shows a miss.
Buffer stock covers the gap while the new shop proves out
The first lots from a new shop often take longer than later ones, and any miss during the trial needs time to correct. Build stock from the outgoing shop before shifting releases, sized to the longest delay you can absorb. Arrangements such as vendor managed inventory, where a supplier holds stock against a forecast, can carry some of that load.
Keep the buffer in place until the new shop has delivered on schedule for the agreed number of lots. Releasing it early turns the first late shipment into a production stoppage.
What about tooling, ownership, and contract terms?
Fixtures, gages, and special tooling may belong to you or to the outgoing shop, and that decides whether they can move and what moving them costs. Ownership, notice periods, and any limits on moving work depend on the agreement between you and the outgoing shop, so review those terms with your contracts or legal team before you tell the outgoing shop about the move.
If the situation is already urgent because the outgoing shop has stopped shipping, a staged plan may not fit the time you have. The guide to getting rush machining when your supplier falls through covers that case. Once the immediate shortage is covered, the steps on this page still apply to the permanent move.
Send FM Machine Co. the Drawing and the Transfer Package
A transfer starts with documents, not a phone call. Drawings at the current revision, the callouts, and the outgoing shop’s inspection data give a new shop what it needs to quote and plan a pilot. These FM Machine Co. pages cover the services a transfer typically touches.
- Precision CNC machining services for the parts being moved
- Machined parts inspection for first article checks and lot verification
- Reverse engineering for parts with missing or outdated drawings
If you are planning to switch machine shops without stopping production, contact us with your drawings and the current shop’s inspection data.