Quotation Validity: Why a Machining Quote Expires in 30 Days
A quote arrives with a line at the bottom that most buyers ignore: "valid 30 days." Six weeks later the buyer issues a PO and discovers the price has moved 4%, and the relationship starts with an argument about whether the shop is honoring its word or protecting its margin.
Neither side is behaving badly. A machining quote is a bet on four variables that the shop does not control, placed on a date when it has no idea when you will order. Understanding which variables and how much they move tells you when to accept a short window, when to ask for a longer one, and what a fair adjustment clause looks like.
What the number on the quote is built from
A machined part price is a stack. For an aluminum bracket in a 200-piece batch, material typically runs 35-55% of the piece price, machine time 25-35%, finishing 8-12%, programming and setup amortized 5-10%, inspection and packaging 3-5%, and margin 8-15%. The mix shifts with the part: a 12 kg hogged-out housing is material-heavy at 55-65%, while a 40 mm turned bushing with two operations is machine-heavy at 45%.
Only two of those lines are exposed to market movement in the short term — material and, through electricity and wages, machine time. The rest are fixed once the process is planned. That is why a shop can hold a price on a small turned part for 60 days and cannot hold one on a plate-heavy housing for 30.
The four inputs that actually move
Metal is the obvious one. Aluminum plate and bar are quoted off an index plus a conversion premium, and the conversion premium moves with mill utilization. When the index moves 6%, the material line moves 6% and the piece price moves 2-3%. Copper alloys and stainless are more volatile in percentage terms but often a smaller share of a machined part.
Currency is the one buyers forget. A Chinese shop quotes in USD but pays wages, power, and much of its tooling in RMB. A move from 7.10 to 6.85 on USD/CNY takes 3.5% off the RMB value of an unchanged dollar price. Shops absorb small moves and reprice at 2-3%.
Energy is regional and seasonal. Guangdong industrial power runs on a tiered schedule, and summer peak rates plus occasional curtailment orders can add 5-8% to the electricity component for a month or two. For a shop running 20 machines at 12 kW average draw, that is real money.
Labor is slow but one-directional. Skilled CNC setters in Shenzhen have seen wage growth in the mid single digits annually, and turnover costs — recruiting, training, scrap during ramp — land in the same bucket.
| Input | Share of piece price | Typical 6-month move | Effect on quote |
|---|---|---|---|
| Aluminum plate and bar | 35-55% | ±5-8% | 2-4% on piece price |
| Copper and brass stock | 20-40% | ±8-12% | 2-5% on piece price |
| USD/CNY | All lines | ±2-4% | 2-4% on piece price |
| Industrial electricity | 3-6% | ±5-8% seasonal | 0.3-0.5% on piece price |
| Skilled labor | 25-35% | +4-6% annual | 1-2% on piece price |
| Anodizing and plating | 8-12% | ±3-5% | 0.3-0.6% on piece price |
See also: How CNC Machining Price Per Part Falls From 1 to 1,000 and What Drives CNC Prototype Cost, Line by Line.
Asking for a validity window that means something
The default 30 days is not arbitrary. It matches the shop's ability to hold a material price with its mill and to keep a machine slot reserved in its planning board. If you need 90 days, ask for 90 days and expect one of three answers: a longer window at a 1-2% premium, a window tied to an index, or a firm price for 30 days with an adjustment mechanism after.
Ask the question in the RFQ, not after the quote. A line like "state your quotation validity and the basis for any adjustment" gets you a usable answer. Ask late and you get the standard 30 days by default.
Two things make a window more credible. First, a named reference price: "based on aluminum at CNY 20,400/t on the Shanghai spot market, 2026-09-30." Second, a stated reprice threshold — the shop will not reopen the price for a 1% index move, only above 3%. A quote with a reference price and a threshold is a quote you can plan a program around.
Writing a price adjustment clause
A workable clause has four parts: the index, the base value, the dead band, and the pass-through ratio.
Take aluminum. Index: the Shanghai spot price for 6061 plate, published weekly. Base: CNY 20,400/t on the quote date. Dead band: no adjustment while the index stays within ±3% of base. Pass-through: 100% of the movement beyond the band, applied to the material line only, not to the whole piece price.
The distinction between material line and piece price is where most of the money is. If material is 45% of the price and the index moves 10%, passing through on the whole price overcharges you by 5.5%. Insist on the material share being stated in the quote, so the arithmetic is checkable.
Add a review cadence — quarterly is usual for a 6-month program, monthly for anything longer — and a symmetric clause. Adjustments should work in both directions; a shop that only reprices upward is not indexing, it is repricing.
Hedging a six-month program
If you have a firm forecast, there are cheaper ways than accepting a 3% risk premium on every lot.
Buy the material forward. A shop can purchase six months of plate at a fixed price if you commit to the volume and pay for it — or pay a 15-20% deposit on the material. That removes the largest variable for both sides at the cost of inventory.
Fix the exchange rate with your bank on the USD amount. A forward contract on USD 300,000 for six months typically costs a fraction of a percent and removes the FX line entirely.
Batch the program. One 3,000-piece run scheduled over three months is easier to price than 500 pieces a month for six months, because the shop can buy material once and hold the price for the whole run. The trade-off is inventory on your side.
Finally, accept a shorter validity on fast-moving items and a longer one on stable ones. A shop quoting stainless 316 with a rising nickel market should offer 14 days, not 60. A shop quoting 6061 with flat indices can hold 90. The window should reflect the volatility of the bill of materials, not a house rule.
Our capabilities page lists the materials and processes we quote most often, and any quote you receive can carry a reference price and a threshold if you ask for them at RFQ stage.
Frequently asked questions
Why do machining quotes expire at all?
Because the shop has priced material, FX, and power at a point in time and cannot hold those inputs indefinitely. A 30-day window matches how long a mill price and a machine slot can realistically be reserved for an order that has not been placed.
Can I get a quote valid for six months?
Yes, usually in one of three forms: a fixed price with a 1-2% risk premium built in, a firm 30 days followed by an indexed adjustment, or a fixed price conditional on you committing volume or prepaying material. The first is simplest and the most expensive.
What is a reasonable dead band on a metal index?
±3% is standard for aluminum over a quarterly review. Below 3% the administrative cost of repricing exceeds the money at stake; above 5% the shop is carrying risk it did not price.
Should the adjustment apply to the whole price or just material?
Just the material line. If material is 45% of the piece price and you index the whole price, a 10% metal move overcharges you by roughly 5.5% of the piece price. Ask for the material share to be stated on the quote so the calculation is transparent.
Related reading
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