The short answer
Deep pockets widen CNC quote bands when depth-to-diameter (or stick-out) forces long tools, rest passes, or specialty holders. Call pocket depth, min inside radius, and whether floors must be flat so [quote-new.php](https://3dwk.com/quote-new.php) **rates.v1.1** estimates stay usable instead of **needs_manual**.
This guide is for buyers RFQing prismatic pockets. Illustrations are **Example part** only. Related: [CNC pockets, thin walls and undercuts](https://3dwk.com/resources/cnc-pockets-thin-walls-undercuts), [when to call out undercuts](https://3dwk.com/resources/when-to-call-out-undercuts-on-cnc-rfq) (publish sibling), [deep-hole drilling](https://3dwk.com/resources/deep-hole-drilling-gun-drilling-cnc).
Reach, L/D and chatter
A 40 mm deep pocket with a 6 mm end mill is a different risk than 12 mm deep with a 12 mm tool. Long stick-out reduces feed and finish quality. Soft materials (PA66 coeff ×0.8 under **rates.v1.1** estimates) deflect; 17-4PH (×1.4) and IN718/IN625 (×2.5) punish reach harder; CoCr (×2.2) likewise. Hot-alloy deep pockets frequently auto-route to **needs_manual** when the mid planning band exceeds configured USD thresholds (e.g. ~$2000 class rules).
Bar $/kg planning bands (estimates): PA66 ~5, 17-4PH ~9, IN718 ~55, IN625 ~60. Material share grows with stock height—see [how stock size changes a CNC quote](https://3dwk.com/resources/how-stock-size-changes-cnc-quote)—but reach time often dominates the mid.
What to put on the drawing
State max depth, min internal corner radius (or “sharp OK / EDM note”), floor flatness if functional, and draft if walls may taper for tool clearance. Prefer larger corner radii so stubbier tools work. If a floor boss sits at the bottom of a deep pocket, mark tool access.
Open deep pockets are **not** undercuts; shadowed lips are. Keep the labels distinct. Related: [DFM checklist](https://3dwk.com/resources/dfm-checklist-before-online-cnc-quote), [3-axis vs 5-axis](https://3dwk.com/resources/3-axis-vs-5-axis-cnc-for-buyers), [datum schemes for multi-setup](https://3dwk.com/resources/datum-schemes-for-multi-setup-cnc-parts).
Illustration 1 shows an **Example part** deep open pocket with radius and depth callouts versus a vague “deep pocket” cloud.
Floor finish, chip evacuation and coolant
Deep floors that need fine Ra may need rest finishing with a stubbier tool after roughing. Chip packing in closed pockets raises risk—add exit paths or say “break for chip clearance OK.” Through-pockets are kinder than blind caverns.
Example part walkthrough
**Example part:** 6061-T6 block ~100×80×50 mm with a 35 mm deep open pocket, 8 mm min corner radius, floor flatness 0.05 to Datum A (top), walls ISO 2768-m. PDF notes “3-axis OK, long-reach accepted” and no undercut lips. Expect a planning band on [quote-new.php](https://3dwk.com/quote-new.php). Same depth with 0.5 mm sharp corners, “Ra 0.4 floor,” and silent access often widens the band or **needs_manual**. Estimates only—Example part, not a customer mold base.
Illustration 2 contrasts a thin deep-pocket note versus a reach-ready RFQ block.
Hot alloys and auto-manual triggers
IN718/IN625 deep pockets combine high time coeffs (×2.5 estimates) with tool wear. If the mid crosses configured thresholds, **needs_manual** is expected even with clear geometry. 17-4PH H900/H1025 (~+$60/lot estimate when configured) after deep milling can move floors—call heat-treat sequence. Related: [what needs_manual means](https://3dwk.com/resources/what-needs-manual-means-preliminary-quote), [reading preliminary quotes](https://3dwk.com/resources/reading-preliminary-online-quote-min-mid-max).
Inspection density
100% CMM of every deep wall at qty 2 is a different inspection narrative than sampling floors only. Say what matters. Related: [CMM vs optical](https://3dwk.com/resources/cmm-vs-optical-measurement-machined-parts), [GD&T callouts that raise bands](https://3dwk.com/resources/gdandt-callouts-that-raise-cnc-quote-bands).
Rest machining and stepped tools
Shops often rough with a long tool then finish floors with a stubbier cutter after opening access. If your PDF forbids step-downs or temporary open features, say so—otherwise assume rest machining is OK. Closed honeycomb pockets without tool entry force EDM or redesign; mark that early.
Bosses rising from deep floors need side clearance for the tool shoulder. If a tall boss sits in a deep pocket with tiny floor fillets, expect chatter or **needs_manual**. Related: [designing bosses and ribs](https://3dwk.com/resources/designing-bosses-and-ribs-for-cnc-housings), [face milling vs peripheral milling](https://3dwk.com/resources/face-milling-vs-peripheral-milling-flatness).
Stock height and buy-to-fly
Deep pockets imply thick starting stock. Extra stock height raises material mass (bar $/kg estimates above) and roughing minutes. If a near-net casting or SLM blank is acceptable, say so on a parallel RFQ rather than forcing solid billet. Related: [how stock size changes a CNC quote](https://3dwk.com/resources/how-stock-size-changes-cnc-quote), [CNC vs die casting vs molding by volume](https://3dwk.com/resources/cnc-vs-die-casting-vs-injection-molding-by-volume).
Fixturing for deep cavities
Soft jaws that grab the outer envelope may crush thin outer walls while you clear a deep inner pocket—call preferred clamp faces. Vacuum fixtures help on large open faces but fail on small footprints. Multi-setup deep parts need datum schemes that survive flips—see [datum schemes for multi-setup CNC parts](https://3dwk.com/resources/datum-schemes-for-multi-setup-cnc-parts).
When qty rises, dedicated fixtures amortize; at qty 1–2, expect the mid to carry more programming and cautious feeds. Quantity breaks help but do not erase physics—see [how quantity breaks change CNC unit cost](https://3dwk.com/resources/how-quantity-breaks-change-cnc-unit-cost).
What to do next
Call depth, min radius, floor needs, then upload on [quote-new.php](https://3dwk.com/quote-new.php). Services: [CNC machining](https://3dwk.com/cnc-machining-service.php), [materials](https://3dwk.com/materials.php). Treat **rates.v1.1** min/mid/max as estimates, not invoices. If **needs_manual** appears, answer reach questions rather than inventing a firm price.
Common questions
Is there a single max depth for CNC pockets?
No. Tool diameter, material, and holder strategy set practical limits. State geometry; let the shop confirm.
Do larger corner radii always lower the mid?
Often they enable shorter tools and higher feed—yes for many prismatics. Tiny radii force long skinny tools.
Are deep pockets the same as deep holes?
No. Holes may use gun drill / peck cycles; pockets are milling reach problems. Use the deep-hole guide for bores.
Will 5-axis erase deep-pocket cost?
Indexed 3+2 can shorten stick-out sometimes, but continuous 5-axis is not a free lunch. Call whether indexing is acceptable.