The short answer
On CNC fixture and tooling RFQs, a **dovetail** and a **T-slot** are not interchangeable workholding features. Dovetails locate and clamp along angled flanks; T-slots accept T-nuts along a tee cavity. Silence on **which feature, which standard size, and which tolerance band** is what widens many [quote-new.php](https://3dwk.com/quote-new.php) **rates.v1.1** estimate bands—not the plate size alone.
This guide is for buyers packaging steel fixture plates where notes say “add clamping slot” without a style. Illustrations use an **Example part** only—not a customer tombstone. Related notes: [how workholding changes CNC quote](https://3dwk.com/resources/how-workholding-changes-cnc-quote), [soft jaws vs vise CNC production lots](https://3dwk.com/resources/soft-jaws-vs-vise-cnc-production-lots), [tool steel A2 D2 O1 CNC fixtures](https://3dwk.com/resources/tool-steel-a2-d2-o1-cnc-fixtures); here we focus on **dovetail vs T-slot labeling**.
What each feature means for quoting
Dovetails need correct included angle, depth, and flank finish; cutters and inspection differ from a T-slot tee. T-slots need throat width, tee width/depth, and often a standard series callout. Process pages for tooling steel ([CNC 3-axis Steel 1018 tooling](https://3dwk.com/en/cnc-3axis/steel-1018/tooling.html), [CNC 3-axis Steel 1018 robotics](https://3dwk.com/en/cnc-3axis/steel-1018/robotics.html), [CNC 3-axis Steel 1018](https://3dwk.com/en/cnc-3axis/steel-1018.html)) assume clear slot geometry when plates mix locating and clamping duties.
Do not bury “slot for clamps” in a cloud. Put **DOVETAIL 60° × DEPTH X / FLANK Ra** or **T-SLOT PER [size series] — THROAT × TEE** on the PDF and RFQ text. Background: [DFM checklist before an online CNC quote](https://3dwk.com/resources/dfm-checklist-before-online-cnc-quote), [datum schemes for multi-setup CNC parts](https://3dwk.com/resources/datum-schemes-for-multi-setup-cnc-parts).
Standards, gauges and mating hardware
When a T-slot must accept a purchased T-nut series, cite the series or attach a gauge sketch. When a dovetail must mate to an existing jaw or clamp block, attach the mating angle and a go/no-go intent rather than “fit existing.” Soft 1018 prototype plates still benefit from that clarity so later tool-steel copies do not reinvent the feature. Fixture buyers who leave mating hardware unnamed force estimators into **needs_manual** even when the outer plate envelope is simple.
Also name whether multiple parallel slots must be coplanar or matched in width—matched banks change inspection packaging under **rates.v1.1** estimates.
Cutter access, heat treat and grind
Deep dovetails may need form cutters or multiple passes; T-slots may need specialized T-slot cutters. If the plate heat-treats after rough CNC, leave grind/skim stock and say so—see [when to specify heat treat after CNC](https://3dwk.com/resources/when-to-specify-heat-treat-after-cnc) and [heat treating steel after CNC machining](https://3dwk.com/resources/heat-treating-steel-after-cnc-machining). Soft 1018 prototypes still need size notes so soft-jaw or vise setups can be planned—see [how workholding changes CNC quote](https://3dwk.com/resources/how-workholding-changes-cnc-quote).
Bar $/kg planning bands (estimates only): Steel 1018 is modest under **rates.v1.1**; feature geometry and post-HT skims drive the band more than the steel line.
Plate thickness and edge distance
Thin plates with deep T-slots risk breakthrough; dovetails near edges need wall stock called out. Put minimum wall and edge distance on the PDF when the feature sits close to plate borders. Robotics/tooling steel pages for 1018 still assume the slot geometry is dimensioned—silent “as required for clamps” is what triggers manual review.
Locating vs clamping duty
Say whether the feature locates the workpiece, clamps it, or both. Mixing a precision dovetail locate with a coarse T-slot clamp on one silent “slot” note invites the wrong toolpath family.
Tolerance and inspection traps
Calling “dovetail to fit” without angle/depth/gauge method forces manual review. Put functional size on flanks or tee and leave non-critical plate envelope at ISO 2768-m. Related: [GD&T callouts that raise CNC quote bands](https://3dwk.com/resources/gdandt-callouts-that-raise-cnc-quote-bands), [what needs_manual means](https://3dwk.com/resources/what-needs-manual-means-preliminary-quote).
Illustration 1 shows an **Example part** plate with labeled dovetail flanks versus a T-slot tee on the same envelope.
Example part walkthrough
**Example part:** Steel 1018 fixture plate ~200×150×25 mm, one central clamping feature, edge dowel holes, ISO 2768-m general. With STEP + **T-SLOT 14 mm SERIES — THROAT/TEE PER TABLE; LENGTH 120 mm CENTERED**, expect a usable automatic planning band on [quote-new.php](https://3dwk.com/quote-new.php). Same geometry with “dovetail or T-slot OK for clamps” often lands **needs_manual**—without inventing any customer tooling PO.
Illustration 2 contrasts a vague slot RFQ versus a labeled dovetail/T-slot pack and the clearer estimate path.
What widens bands fastest
Unlabeled mix of dovetail and T-slot, missing angle or tee sizes, HT-after-CNC without skim stock, and 100% gauge of every flank without a method. Quantity breaks help unit minutes but do not erase feature ambiguity—see [how quantity breaks change CNC unit cost](https://3dwk.com/resources/how-quantity-breaks-change-cnc-unit-cost) and [prototype vs production CNC quotes](https://3dwk.com/resources/prototype-vs-production-cnc-quotes).
What to do next
Pick **dovetail** or **T-slot**, add size/angle/depth, note HT/skim if any, then upload on [quote-new.php](https://3dwk.com/quote-new.php). Service pages: [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.
Common questions
Is a dovetail always tighter than a T-slot?
Not inherently—it depends on the tolerance pack. Locating dovetails are often held tighter; clamping T-slots may be looser. State the duty.
Can I write “slot compatible with our clamps”?
Only if you attach a size standard or gauge drawing. Otherwise estimators guess.
Does tool steel change the advice?
Yes for wear and HT sequence—see [tool steel A2 D2 O1 CNC fixtures](https://3dwk.com/resources/tool-steel-a2-d2-o1-cnc-fixtures)—but feature labeling still comes first on 1018 prototypes.
Should soft jaws copy the same feature?
If jaws mate to the dovetail/T-slot, name that interface—see [soft jaws vs vise CNC production lots](https://3dwk.com/resources/soft-jaws-vs-vise-cnc-production-lots).