A Drawing Came In Missing Three Dimensions. We Added a 30% Risk Premium.
A drawing arrived last week with three dimensions missing. We didn't guess at the values. We added a 30% risk premium — and a note explaining exactly why. A quote is a promise, and we price the risk we can see rather than pretend it isn't there.
The Drawing
It was a straightforward machined block — until you looked for the locating features. Three dimensions that the assembly clearly depended on were simply absent: no callout, no note, nothing in the model to infer them from. Not a typo. A gap.
This happens more than buyers realise, especially with drawings that started life as a sketch and got promoted to a production print without a full review. The instinct of many shops is to fill the gap quietly: assume a reasonable value, quote low, and hope the part fits.
We don't do that. Here's what a missing dimension actually costs, and why we put it on the line item.
Two Options, Both Real
A missing dimension is never free. It forces one of two choices:
1. Stop and ask
The correct-looking move. But it stalls the quote, and once the job is booked it stalls the job. Every day of clarification is a day of lead time the customer didn't plan for. Reasonable for a one-off; painful across a production schedule.
2. Assume a value
Faster, but the risk is real: if the assumed value is wrong, the part doesn't fit, and the scrap and rework land on someone's account. In a production run that someone is usually the shop — and a 30% premium is the floor on what that exposure is worth.
Why We Price the Visible Risk
We added 30% to the quote and wrote one line: "Three dimensions not specified on drawing; premium covers interpretation and rework exposure. Send the values to remove it."
That does two honest things. It tells the customer the real cost of the gap, instead of burying it in a low number that will surface as a delay or a reject later. And it gives them an easy off-ramp: send the three numbers and the premium disappears.
Most shops quietly absorb this risk or quote the optimistic case. Both are a kind of lie — the first by omission, the second by pretending the drawing is complete. We'd rather show the premium than win an order on a number we know is wrong.
| Approach to a missing dimension | What the customer sees | Where the risk lands |
|---|---|---|
| Quote low, assume the best case | A cheap number | On the shop, at scrape time |
| Stop and ask before quoting | A delay, then a clean price | On the schedule |
| Transparent risk premium | The exposure, on the line item | Shared, and removable |
| Our choice | Premium shown, customer decides | |
How to Avoid the Premium Entirely
It's almost always preventable, and the fixes are cheap when applied early:
- Send the drawing before you freeze the design. A fifteen-minute review catches missing dimensions before they become a quote problem.
- Define a clear datum. Most "missing" dimensions are really undefined references. Lock the datum and the rest follows.
- Run a first article. Prove the process on part one, not part ten thousand. We describe exactly how in our quality and documentation process.
- Talk before PO. The cheapest, highest-leverage step in the whole job is a conversation about any unclear callout — before money changes hands.
For the symbols and reference frames that prevent these gaps, our GD&T notes for buyers and the tolerance chart are a good place to start.
A Quote Is a Promise
The lesson isn't "always send perfect drawings" — everyone slips. The lesson is that a low quote on an incomplete drawing isn't a bargain; it's a promise the shop can't keep, paid for later in delays or rejects. A transparent premium is the opposite: a number you can act on.
We publish our full approach to inspection and documentation so you can see exactly what you're buying — including what we'll show you before you pay a cent. Read our quality control page, then send the drawing. If three numbers are missing, we'll tell you, and the premium comes off the moment they arrive.
Incomplete Drawings
What happens if a CNC drawing is missing dimensions?
Why add a risk premium instead of just asking?
How do I avoid missing-dimension surprises on my quote?
Do you quote the risk you can't see?
Send the Drawing — We'll Flag the Gaps
If you're not sure a drawing is complete, send it anyway. We'll tell you what's missing before we quote, so the number you get is the number you pay — no premium, no surprise. Our full inspection and documentation process is here.