The short answer
For CNC machined 17-4PH, specify the heat-treat condition (H900, H1025, or other), which features need tight fits versus ISO 2768-m general tolerances, and whether passivation or other finishes apply after aging. Buyers who only write “17-4 stainless, tight” get ambiguous quotes and rework. Callouts that name condition, datums, and functional tolerances let shops quote machine time and secondary ops honestly.
This guide is for engineers and purchasing teams writing RFQs for precipitation-hardening stainless. Ranges below reflect typical shop practice plus 3DWK quote-engine **rates.v1.1 estimate bands** (material and machining multipliers)—not a locked factory quote. Upload STEP + drawing on [quote-new.php](https://3dwk.com/quote-new.php) for a preliminary range.
Why 17-4PH needs clearer RFQs than 304/316
17-4PH (UNS S17400) is usually bought as solution-annealed bar or plate, then aged to H900, H1025 or similar after rough or finish machining. Strength, hardness and dimensional stability shift with that aging step. Unlike 304/316, you cannot assume “stainless as machined” covers the final condition. Related alloy context: [stainless 304 vs 316 vs 17-4PH](https://3dwk.com/resources/stainless-304-vs-316-vs-17-4ph) and [heat treating steel after CNC](https://3dwk.com/resources/heat-treating-steel-after-cnc-machining).
Machinability is also tougher than aluminum or soft stainless. **rates.v1.1** applies a CNC machine-time factor of about **×1.4** versus baseline aluminum-class rates, with bar stock around **$9/kg (estimate)**. Heat treat H900/H1025 is modeled as about **+$60/batch (estimate)** when the line is auto-priced. Treat those as planning bands until a factory calibrates them.
What buyers should specify on the drawing
1. **Material + condition intent:** “17-4PH, machine annealed, age to H900” or “supply H1150 bar, machine finish.” State whether aging happens before finish machining of critical fits.
2. **Datums and functional fits:** Mounting faces, pin holes, sealing diameters—use GD&T or bilateral limits where assembly cares. Elsewhere ISO 2768-m (or your house general tolerance) is enough. See [GD&T basics for buyers](https://3dwk.com/resources/gdt-basics-for-buyers).
3. **Threads and holes:** Call standard tapped sizes; note if thread after aging (tap may need adjustment). Reaming/boring guidance: [reaming vs boring](https://3dwk.com/resources/reaming-vs-boring-cnc-hole-size).
4. **Surface:** As-machined Ra, or Ra 1.6 / 0.8 only where sealing or sliding needs it ([surface roughness Ra](https://3dwk.com/resources/surface-roughness-ra-for-machined-parts)).
5. **Finish after aging:** Passivation is common; electropolish is a separate ask ([passivation vs electropolishing](https://3dwk.com/resources/passivation-vs-electropolishing-stainless)).
6. **Quantity, certs, inspection:** Mill certs, hardness check after aging, FAIR if required ([FAI reports](https://3dwk.com/resources/first-article-inspection-reports)).
Illustration 1 shows a practical tolerance stack: general vs functional vs post-age criticals.
Example part (not a customer case)
**Example part:** a 17-4PH sensor mount roughly 80×50×20 mm with four M4 mounts, one Ø8 H7 bore for a locating pin, and a sealing face flat to 0.05 mm. Annotate as Example part in RFQ notes so nobody mistakes it for a live order photo.
Illustrative **rates.v1.1** planning band for a similar one-off CNC line (material + machine time + H900 batch share, ± about 12% public range display): often lands in a few hundred USD depending on setups and finish—not a promise. Lines that grow complex can trip manual review. Confirm on [quote-new.php](https://3dwk.com/quote-new.php).
Tolerance strategy that keeps cost down
- Hold tight only on mates; leave pockets and non-functional edges on general tolerance ([CNC pockets, thin walls](https://3dwk.com/resources/cnc-pockets-thin-walls-undercuts)).
- Decide whether critical bores are finished **after** aging (better size control, more ops) or before (risk of age movement).
- Avoid stacking ±0.01 mm everywhere—shops will either inflate price or ask for clarification ([CNC cost drivers](https://3dwk.com/resources/cnc-machining-cost-drivers-buyer-guide)).
- Edge breaks: call a default chamfer/deburr instead of silent sharp edges ([edge break callouts](https://3dwk.com/resources/edge-break-chamfer-deburr-callouts-cnc)).
Illustration 2 contrasts a vague RFQ with a condition + datum + fit RFQ and how quote confidence changes.
Lead time and process notes
Calendar time still tracks stock, aging furnace batching, finish and inspection—not only cycle minutes ([CNC lead time guide](https://3dwk.com/resources/cnc-machining-lead-time-buyer-guide)). **rates.v1.1** CNC standard lead bands are roughly **7–12 days** planning guidance; aging adds furnace queue. Expedite is a separate uplift conversation.
If geometry forces many angled faces, say so—process may move toward 3+2 ([3-axis vs 5-axis for buyers](https://3dwk.com/resources/3-axis-vs-5-axis-cnc-for-buyers) when live, or five-axis housing tips).
Common mistakes
- Writing “17-4PH” with no H-condition.
- Tightening every dimension after a failed fit instead of fixing datums.
- Ignoring that passivation does not fix size; it is chemistry, not machining.
- Expecting wrought 316 quotes to transfer 1:1 to aged 17-4PH machine time.
What to do next
Export STEP + PDF with condition, datums and functional tolerances. Upload on [quote-new.php](https://3dwk.com/quote-new.php). Related: [CNC machining service](https://3dwk.com/cnc-machining-service.php), stainless comparison, heat treat after CNC, GD&T basics, cost drivers.
Inspection language that matches the tolerances
If you tighten a bore to H7 and a face to 0.02 mm flatness, say how you will accept the part: CMM, gauge pins, or optical ([CMM vs optical](https://3dwk.com/resources/cmm-vs-optical-measurement-machined-parts)). Orphan tight tolerances without a measurement plan create disputes. For first articles, reference your FAIR expectations once ([FAI reports](https://3dwk.com/resources/first-article-inspection-reports)).
Buyers sometimes copy aerospace-looking blocks into commercial drawings. That inflates cost without adding function. Prefer a short note: “Functional fits as dimensioned; other features ISO 2768-m; age to H900 after rough; finish Ø8 H7 and sealing face after age.”
Stock and blanking notes worth one RFQ line
Tell the shop if the blank must be cut from plate versus turned from bar, or if grain direction matters for a fatigue-critical arm. 17-4PH plate and bar can differ in availability. If you already have remnant material, say so—lead time collapses when stock is customer-supplied ([lead time guide](https://3dwk.com/resources/cnc-machining-lead-time-buyer-guide)).
Comparing to 304/316 quotes
A prior 316 quote is a weak predictor for aged 17-4PH. Hardness after H900 changes tooling and feeds; the **×1.4** time factor in **rates.v1.1** is a planning reminder, not a full cutting study. Passivation callouts also differ in practice from “bright stainless cosmetics.” Keep the stainless comparison article open while you edit the drawing, then price the real alloy on the quote page.
Checklist before you hit upload
- Condition and sequence written
- Datums visible on PDF
- Only functional limits tightened
- Finish after age named
- Qty and inspection level set
- Example-part demos labeled if the file is only a study
Then open [quote-new.php](https://3dwk.com/quote-new.php). If the engine returns a range, read min/mid/max as planning; if **needs_manual**, attach the heat-treat note and wait for engineering—both are success paths.
Common questions
Do I always need H900?
No. H900 is common for high strength; H1025/H1150 trade strength for toughness or stability. Match the condition to the design requirement, then put it on the drawing.
Can shops hold ±0.01 mm on every feature in 17-4PH?
Usually not economically. Reserve fine limits for fits; use general tolerances elsewhere.
Does heat treat always happen after CNC?
Often rough machine → age → finish criticals, or age bar then machine. State the sequence you need for size-critical features.
Will the online quote always show a number for 17-4PH?
**rates.v1.1** can show an estimate band when geometry parses; complex or high lines may return **needs_manual**. That is expected—not a dead quote.