QuotedPartCost guides · Updated 2026-10-30
How much should I charge extra for tight tolerances?
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At ten pieces, this plate is $57.75 each with a ±0.005-inch general tolerance, versus $73.52 at ±0.001 and $84.57 at ±0.0005 under the explicit extra-operation allowances. Charge for the route and acceptance risk rather than adding the same percentage to every tight dimension.
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Keep geometry constant while changing the requirement
The reference is a 4 × 3 × 0.75-inch 6061 plate from 0.875-inch stock, with two quarter-inch holes and a 2 × 1 × 0.25-inch pocket. It is deliberately simple enough to isolate tolerance. Each variant uses the same material, feature dimensions, quantity and work-center rates. The general tolerance note changes, along with the manually stated finish and inspection allowances.
The middle case adds fifteen finishing setup minutes and three finishing minutes per part at $95/hour, plus twenty inspection setup minutes and two measuring minutes per part at $75/hour. The tightest adds the same fixed setup allowances but six finishing and five measuring minutes. These are hypothetical routing choices, not an automatic guarantee that a machine can hold the requested band.
| Tolerance | Run min/part | Base sell/part | Illustrative reject reserve | With reserve/part |
|---|---|---|---|---|
| ±0.005 in | 8.00 | $57.75 | 0% | $57.75 |
| ±0.001 in | 13.00 | $73.52 | 2% | $75.02 |
| ±0.0005 in | 19.00 | $84.57 | 5% | $89.02 |
Separate size, position and measurement access
A pocket width measured with an accessible gauge is a different problem from a position tolerance tied to several datums. Flatness after unclamping, thin walls and temperature can create acceptance work not described by a single plus/minus number. Ask which feature is functional and how the customer will inspect it before selecting the process.
A grind, hone, lap or dedicated workholding is not included in these milled-plate variants. Add the actual operation if the feature requires it. A tolerance requirement can also make stock condition and roughing sequence important; paying for another finishing pass does not automatically correct material movement after the part leaves the vise.
Yield is an assumption that should have evidence
The reserve column demonstrates zero, two and five percent anticipated rejection. Those values are illustrative, not measured shop scrap rates. The final column divides the base selling price by accepted yield. It is a simple reserve model, not a full simulation of parts rejected at different stages; it should not replace a job-specific analysis of where money is lost.
Do not add a rejection reserve if the same risk is already included in a separate contingency or inflated cycle. When a repeat job has reliable yield history, use that record. When there is no history, show the assumption internally and explain any first-article or process-development charge to the buyer.
The cheapest useful change is often narrowing the requirement to functional features. A blanket tight general tolerance can force unnecessary measurements on noncritical faces. Request an approved drawing change rather than quietly applying a looser shop default, then rerun the estimate with the revised scope.
Tolerance scenario inputs
- • 6061 plate4 ×3 ×0.75 in, raw0.875 in; twoØ0.25 holes; pocket2 ×1 ×0.25 in, R0.125. Ten parts.
- • Base generated route plus described finishing/inspection allowances at$95/$75h. 30% markup, no automatic rules, $65 line floor.
- • Reject reserves0/2/5% are hypothetical. Final reserve arithmetic=engine selling price/(1-reserve). No grinding, controlled-room charge, certs, tax or freight.
| Tolerance | Run min/part | Base sell/part | Illustrative reject reserve | With reserve/part |
|---|---|---|---|---|
| ±0.005 in | 8.00 | $57.75 | 0% | $57.75 |
| ±0.001 in | 13.00 | $73.52 | 2% | $75.02 |
| ±0.0005 in | 19.00 | $84.57 | 5% | $89.02 |
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