QuotedPartCost guides · Updated 2026-10-30
How much do Ra 32 and Ra 16 surface finishes add to machining cost?
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At ten plates, the ordinary milling scenario is $51.47 each, the planned 32-microinch Ra route is $63.99 and the 16-microinch grinding route is $74.66. Those differences buy stated operations and measurements. A roughness number alone does not determine either cycle time or a guaranteed finishing process.
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Read the units and the surface boundary first
The reference is a 4 × 3 × 0.5-inch 1018 plate with two quarter-inch holes, a ±0.005-inch general tolerance and one specified twelve-square-inch face. We compare 125, 32 and 16 microinches Ra on that face. In metric terms, 32 microinches is approximately 0.81 micrometer and 16 is approximately 0.41. A bare 'Ra 16' note needs its units resolved before quoting.
Keyence describes Ra as average profile roughness and distinguishes it from other roughness parameters. It also explains that process, tool condition and cutting parameters affect the result. Ra does not specify flatness, parallelism, waviness or a dimensional fit. Ask for the drawing's measurement method and surface extent rather than assuming one callout covers every aspect of the face.
| Face requirement and planned route | Qty | Setup min/lot | Run min/part at qty | Stock | Setup | Machine/labor | Outside | Markup + floor | Sell/part |
|---|---|---|---|---|---|---|---|---|---|
| 125 µin Ra: ordinary milled face | 1 | 137.5 | 8.90 | $16.98 | $209.04 | $12.69 | $0.00 | $71.61 | $310.32 |
| 125 µin Ra: ordinary milled face | 10 | 137.5 | 8.90 | $5.99 | $20.90 | $12.70 | $0.00 | $11.88 | $51.47 |
| 125 µin Ra: ordinary milled face | 100 | 137.5 | 8.90 | $3.71 | $2.09 | $12.70 | $0.00 | $5.55 | $24.05 |
| 32 µin Ra: controlled finish pass | 1 | 162.5 | 12.90 | $16.98 | $245.29 | $18.69 | $0.00 | $84.29 | $365.25 |
| 32 µin Ra: controlled finish pass | 10 | 162.5 | 12.90 | $5.99 | $24.53 | $18.70 | $0.00 | $14.77 | $63.99 |
| 32 µin Ra: controlled finish pass | 100 | 162.5 | 12.90 | $3.71 | $2.45 | $18.71 | $0.00 | $7.46 | $32.33 |
| 16 µin Ra: planned surface grind | 1 | 177.5 | 16.90 | $16.98 | $267.38 | $24.68 | $0.00 | $92.71 | $401.75 |
| 16 µin Ra: planned surface grind | 10 | 177.5 | 16.90 | $5.99 | $26.74 | $24.70 | $0.00 | $17.23 | $74.66 |
| 16 µin Ra: planned surface grind | 100 | 177.5 | 16.90 | $3.71 | $2.67 | $24.71 | $0.00 | $9.33 | $40.42 |
Choose a route, then price its extra work
The 32-microinch scenario adds fifteen VMC setup minutes and three minutes per plate for controlled finishing at $95/hour, followed by ten inspection setup minutes and one minute per plate at $75/hour. These are explicit estimator allowances. They do not prove that a particular cutter and steel condition will meet the requirement without a trial.
The 16-microinch route instead adds an example surface-grinding center at $95/hour, twenty-five setup minutes and six minutes per part. Post-grind roughness and dimensional checks add fifteen setup minutes and two minutes per plate at inspection. This center is an example input, separate from the catalog's cylindrical grinder. The part receives the base conservative milling route before grinding; no claimed milling-time credit has been taken.
| Operation | Rate/h | Setup min/lot | Run min/part | Other lot | Other/part |
|---|---|---|---|---|---|
| CAM programming, 6 toolpaths | $95.00 | 49 | 0 | $0.00 | $0.00 |
| Mill, 2 setups | $95.00 | 67.5 | 6.5 | $0.00 | $0.00 |
| Deburr | $55.00 | 5 | 1.8 | $0.00 | $0.00 |
| Inspect | $75.00 | 16 | 0.6 | $0.00 | $0.00 |
| Grind one specified face | $95.00 | 25 | 6 | $0.00 | $0.00 |
| Roughness and post-grind dimensions | $75.00 | 15 | 2 | $0.00 | $0.00 |
A fine finish should apply where function requires it
The grinding estimate covers one accessible face. It excludes heat treatment, special magnetic or mechanical fixturing, lapping, coating and dedicated gauge purchase. A thin, interrupted or inaccessible surface may need a different holding method. Grinding also requires an agreed stock allowance and datum sequence before the drawing can be released to production.
Each case uses the same $2.46/lb small-lot and $1.40/lb volume steel inputs, $95 programming and milling, $55 bench work and $75 inspection. Prices include 30% markup and a $65 line minimum. The material rates are catalog assumptions, not live vendor offers. Quantity-adjusted operation minutes appear in the estimate.
If only a seal land needs the finer finish, have the designer mark that region rather than applying it globally. Changing the note without approval is not a valid cost reduction. Compare the cost of the accepted surface, its inspection and any post-treatment rework together; an inexpensive pass that cannot be verified is not a complete finishing quote.
Face-finishing inputs
- • 1018 plate4 ×3 ×0.5 in, raw0.625 in, twoØ0.25 holes; ±0.005 in. Only one12 in² face changes:125/32/16 µin Ra; quantities1/10/100.
- • 32µin: VMC15 setup+3 run min; inspect10+1. 16µin: example surface grind25+6 at$95/h; inspect15+2 at$75/h. Added times are hypothetical process allowances, not finish guarantees.
- • Same base material and generated route; 30% markup, $65 minimum, no rules; quantity learning active. No heat treat, special fixtures, dedicated gauge, flatness guarantee, tax or freight.
| Face requirement and planned route | Qty | Setup min/lot | Run min/part at qty | Stock | Setup | Machine/labor | Outside | Markup + floor | Sell/part |
|---|---|---|---|---|---|---|---|---|---|
| 125 µin Ra: ordinary milled face | 1 | 137.5 | 8.90 | $16.98 | $209.04 | $12.69 | $0.00 | $71.61 | $310.32 |
| 125 µin Ra: ordinary milled face | 10 | 137.5 | 8.90 | $5.99 | $20.90 | $12.70 | $0.00 | $11.88 | $51.47 |
| 125 µin Ra: ordinary milled face | 100 | 137.5 | 8.90 | $3.71 | $2.09 | $12.70 | $0.00 | $5.55 | $24.05 |
| 32 µin Ra: controlled finish pass | 1 | 162.5 | 12.90 | $16.98 | $245.29 | $18.69 | $0.00 | $84.29 | $365.25 |
| 32 µin Ra: controlled finish pass | 10 | 162.5 | 12.90 | $5.99 | $24.53 | $18.70 | $0.00 | $14.77 | $63.99 |
| 32 µin Ra: controlled finish pass | 100 | 162.5 | 12.90 | $3.71 | $2.45 | $18.71 | $0.00 | $7.46 | $32.33 |
| 16 µin Ra: planned surface grind | 1 | 177.5 | 16.90 | $16.98 | $267.38 | $24.68 | $0.00 | $92.71 | $401.75 |
| 16 µin Ra: planned surface grind | 10 | 177.5 | 16.90 | $5.99 | $26.74 | $24.70 | $0.00 | $17.23 | $74.66 |
| 16 µin Ra: planned surface grind | 100 | 177.5 | 16.90 | $3.71 | $2.67 | $24.71 | $0.00 | $9.33 | $40.42 |
Sources and limits
Claims are dated where they can change. Product calculations are examples from the stated inputs, not a promise about a customer's quote. Competitor wording is attributed to the source shown.
- Keyence distinguishes Ra from other roughness parameters and explains that process and tooling affect achieved surface finish. — source (checked 2026-10-30)
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