Leave a practical cutting path
Check the direction of entry, pocket depth, cutter reach and holder clearance. A feature that is visible in CAD can still be blocked by a wall, boss or fixture.
CNC Design Guidelines for Machinable Parts
Practical DFM rules for walls, holes, fillets, and drawings — so your CAD is ready for quoting and machining.
When this guide applies
Use these CNC design guidelines to check tool access, walls, holes and threads, then prepare a controlled drawing package for DFM. Identify functional features, material and finish, and connect critical requirements to the intended inspection scope before requesting a quote.
Start with what the part must do: support a load, locate an assembly, carry motion or seal an interface. Mark the features that protect those functions. The checklist below helps you explain that intent while reviewing how a cutter, fixture and measuring tool can reach the part.
For broader engineering reference, view the Jaquent CNC Design Engineering Guide, Rev E (PDF) or download the PDF. The handbook is a separate versioned reference; confirm project requirements through the controlled drawing and DFM review.
Tool access, pockets and workholding
Choose internal radii around the toolpath
Milled internal corners retain a cutter radius. A small radius in a deep pocket can require a slender tool and longer reach; discuss a larger radius or local relief where the mating part permits it.
Keep chamfers and corner radii distinct
An edge chamfer breaks an edge or helps assembly. It does not remove the cutter radius along an internal pocket corner. Mark a functionally necessary sharp internal corner for process review.
Reserve stable locating and clamping surfaces
Show which faces must remain functional or cosmetic and which areas may support the part during machining. Consider how datums and inspection access survive later operations.
Walls, ribs and material stiffness
| Feature or material | What to review | What to share for DFM |
|---|---|---|
| Tall walls or long unsupported spans | Wall thickness together with height, span, tool forces and clamping. | Identify flexible regions; discuss shorter spans, ribs or support where function permits. |
| Aluminum walls and floors | Local stiffness and movement during stock removal and unclamping. | Grade and temper, stock form if constrained, functional faces and final measurement state. |
| Stainless and carbon steel walls | Material condition, cutting load and whether later heat treatment changes the requirement. | Exact grade and condition, heat-treatment sequence and the surfaces that control assembly. |
| Engineering plastics | Grade, temperature/moisture effects, clamping and free-state movement. | Material specification, wall height/span and agreed support or restraint during inspection. |
Note
Thickness alone does not define a guaranteed machining limit. Review the whole feature before accepting a thin wall. Where geometry may change, use smooth transitions and discuss ribs or extra support without obstructing the assembly or cutting path.
Hole diameter and depth
| Hole type | Define on the drawing | Review before release |
|---|---|---|
| Through hole | Diameter, location, entry/exit faces and edge condition. | Breakthrough access, exit burr removal and nearby thin features. |
| Blind drilled hole | Required full-diameter depth and any functional bottom requirement. | Drill-point space, chip evacuation and the distinction between usable depth and total drilled depth. |
| Precision bore or seat | Fit or size limits, required form/location and acceptance state. | Finishing allowance and a measurement approach that supports the required characteristic. |
| Deep or intersecting hole | Diameter, usable depth, intersections and deburring requirements. | Depth-to-diameter ratio, tool reach, chip removal and access to verify internal intersections. |
Note
Define what the hole must accommodate before selecting a drilling or finishing route. A blind hole does not have a universal diameter increment or bottom fillet. Show whether a flat bottom, full-diameter depth or clearance for a mating component is functional; agree the method through DFM.
Threads and inserts
State the thread designation, nominal size, pitch or threads per inch, tolerance class / fit and handedness. For a blind threaded hole, distinguish usable full-thread depth, runout or relief, and total drilled depth, including room for the tool and chips. An assembled screw needs usable engagement and bottom clearance.
For inserts, supply the insert specification and required installed condition. Identify whether the thread is accepted before or after finishing, whether it is masked, and which gauge or other inspection requirement must be included in the quote.
Inch dimensions, UNC/UNF threads and ASME Y14.5 requirements need project-specific DFM and inspection-plan confirmation. State the drawing standard and edition rather than relying on the CAD unit setting alone.
Illustrative blind-thread handoff: If the assembly needs 10 mm of usable full thread, show its start relative to the entry face and record that minimum separately from the maximum permitted drilled depth and minimum remaining bottom wall. Ask DFM to reconcile those requirements with entry chamfer, tap lead or thread-milling clearance, drill-point space and screw bottom clearance. This example gives no recommended extra drilling depth or guaranteed engagement strength.
Functional features, datums and inspection inputs
Use consistent feature names or balloon IDs across the model, drawing and requested inspection records. Identify fits, mounting relationships, sealing faces, burr-sensitive edges and required surface texture. Specify the general tolerance and individually controlled features with the appropriate datum references where needed. See functional tolerances and GD&T.
Teaching example: a mounting bracket
For a bracket that rests on a base, uses a side face for orientation and a selected hole for location, explain those three functions before adding geometric controls. Check whether the support face can be held without damaging it, whether the hole is reachable and whether later operations preserve the locating features. This is a synthetic design example, not a customer part or a machining result. The tolerance guide handles the requirement choices; inspection scope and required reports covers evaluation and records.
If a bore, thread or sealing face must be accepted after coating or heat treatment, mark that state and its masking or allowance requirements. Agree changes with the drawing owner and return accepted DFM changes to the controlled revision. See surface finishes and fit allowances.
Recommended drawing formats
STEP model and marked PDF
Use a STEP (.step / .stp) model for geometry and a PDF drawing for controlled requirements. Match the part number, revision and units; mark the features that need particular attention.
Resolve differences before production
State the agreed precedence of model, drawing and PO information. Ask for clarification if geometry or notes disagree; an accepted DFM change belongs in the controlled package.
Alternative engineering files
Direct uploads also accept .igs, .x_t, .prt and .sldprt, plus .zip / .rar archives. For .iges, DWG, DXF or .sldasm, export suitable STEP/PDF or contact Jaquent to confirm delivery and dependencies. An accepted archive does not confirm its contents can be read.
Keep the RFQ practical
Attach up to 5 files totaling 25 MiB. The checklist describes useful review inputs; attachments, material and quantity remain optional form fields.
What to include in your machining RFQ
| Information | Why it helps | If it is unclear |
|---|---|---|
| STEP + marked PDF; part number and revision | Keeps geometry and controlled requirements together. | Which files represent the current revision, and what takes precedence if they differ? |
| Units, drawing standards and editions | Makes dimensions and callouts interpretable. | Are any inch, UNC/UNF or ASME requirements included for project-specific review? |
| Material grade and condition | Supports stock, process and movement review. | Which grade, temper, heat treatment and material records are required? |
| Quantity, batch intent and target delivery | Supports the route, capacity and quotation. | Is this a prototype, pilot batch or repeat order, and what date is needed? |
| Functional features, individual limits and applicable datums | Focuses DFM and inspection on the required relationships. | Which interfaces determine fit, location, motion or sealing? |
| Finish, masking and acceptance state | Connects the final-use condition with manufacturing. | Which features are accepted after finishing, and who checks them? |
| Coverage and required records | Lets the quote include the requested checks and documents. | Which named features need every-part checks or agreed sampling, and which reports or customer forms must be quoted? |
Note
Recommended preparation inputs for engineering and purchasing. Submit what you have and identify open questions; the RFQ requires a project summary, name, company and email, while attachments and technical details are optional. The list does not authorize a supplier to change the controlled CAD or drawing.
Plan one critical feature
| Planning field | Your input |
|---|---|
| Feature ID | ________________ |
| Drawing / revision | ________________ |
| Function and requirement | ________________ |
| Datums (where applicable) | ________________ |
| Acceptance stage / state | ________________ |
| Proposed inspection method | ________________ |
| Coverage | ________________ |
| Required record | ________________ |
Note
Use one entry for a selected feature. Leave the method as proposed until DFM / the inspection plan confirms it. Agree every-part or sampled coverage and the required record separately; a first-article form does not define ongoing production coverage. This blank planning item contains no measurements or acceptance verdict.
Drawing preparation questions
Is a STEP model enough for a quote?
A STEP model communicates geometry. A marked PDF helps communicate controlled dimensions, general tolerances, material, finish, revision and critical features. Share what is available and identify open requirements for DFM review.
Should I use one minimum wall thickness for every material?
Review thickness together with height, free span, material, clamping and acceptance state. Mark flexible features so a support strategy or geometry change can be discussed for that part.
What should I specify for a blind threaded hole?
Give the thread designation, size, pitch, class / fit, handedness and usable full-thread depth. Distinguish thread runout or relief from total drilled depth, and identify finishing and inspection needs.
Where do I send the design package?
Use STEP (.step / .stp) and a marked PDF drawing when available. Direct uploads accept .stp, .step, .igs, .x_t, .prt, .sldprt, .pdf, .zip and .rar. For .iges, DWG, DXF or .sldasm, export suitable STEP/PDF or contact Jaquent to confirm delivery and dependencies. Archives count toward the limits; acceptance does not confirm readability. Attach up to 5 files totaling 25 MiB. Attachments, material and quantity remain optional form inputs.
Request a Quote. With a complete RFQ, we typically respond within one business day; complex multi-process projects may take 1–2 business days.
Ready to start your CNC project?
Share CAD, a controlled drawing and your open design questions for a DFM review and quotation.