CNC Machining & Injection Molding — DFM/Moldflow Support, CMM Inspection, Prototype to Production Solutions.
Swiss CNC Tolerance Review
Suitable turned features may use ±0.01 mm as a practical review baseline. Selected critical outside diameters may be reviewed to ±0.005 mm, but this does not apply automatically to the complete part.
Define each CTQ by datum, material condition, finish stage and inspection method.
Send a controlled 2D drawing and matching 3D model.
Direct Tolerance Answer
No single tolerance applies to an entire Swiss-turned part. Review every CTQ by geometry, material, datum, process stage and measurement method.
A practical starting point for suitable turned diameters after feature-level drawing review.
Selected outside-diameter CTQs may be reviewed to this level when support, tooling, thermal stability and inspection capability align.
This level usually requires grinding or another controlled finishing process—not Swiss turning alone.
Tolerance Review Matrix
Review each feature as a separate CTQ where function requires it. Use these ranges only to begin drawing review; final requirements depend on geometry, material, support, process stage and inspection access.
| Feature | Review Starting Point | Main Variables | Verification |
|---|---|---|---|
| Controlled turned OD | Around ±0.01 mm; selected CTQs to ±0.005 mm after review. | Material, support, wear, temperature | Micrometer, laser or comparative gauge |
| Step / shoulder length | Approximately ±0.02–0.05 mm | Tool path, cutoff, datum origin | Optical comparator or CMM |
| Runout | Down to 0.01 mm TIR after datum review | L/D, bar straightness, measurement support | Indicator, fixture or CMM |
| Cross-hole position | Approximately ±0.02–0.05 mm | Indexing, breakthrough, burr control | Optical, CMM or pin method |
| Small bore | Review separately; no blanket range | Depth, chips, wall stiffness, access | Plug, air, optical or CMM |
| Threads | Define class and functional acceptance | Wear, plating, thread start | Go/No-Go or functional gauge |
| Surface finish | Ra 0.8–1.6 µm may be typical; Ra 0.4 µm requires review | Alloy, feed, tool radius, finishing | Profilometer |
Process Conditions
A drawing tolerance is realistic only when the full process controls variation. Geometry, bar stock and production conditions can make the same dimension behave differently.
Keep cutting close to effective guide-bushing support. Longer spans increase bending, chatter and taper.
Cutting force deflects small sections; tool wear shifts diameter and finish across a batch.
Straightness, roundness, diameter consistency and surface condition affect guide-bushing stability.
Work hardening, chip formation and residual stress change heat, tool load and distortion.
Machine warm-up, coolant stability and inspection temperature can shift measured size.
Geometric Control Logic
These controls answer different functional questions. A diameter can meet its size limit while the axis runs out, and a correctly sized cross-hole can still be misplaced.
Limits a stated diameter, length or bore. It does not control the feature’s relationship to a datum or another feature.
Controls surface variation as the part rotates about a defined datum axis. Specify circular or total runout and the measurement setup.
Locates a hole, slot, axis or center plane from specified datums. Feature size and positional acceptance are evaluated separately.
CTQ Measurement Plan
A CTQ is actionable only when its datum, access, measurement direction and inspection stage are defined. Select the method for functional risk—not equipment preference.
Micrometer for accessible diameters; laser or comparative gauging when required by the control plan.
Pin or plug gauges for function; air, optical or CMM methods when measured data are required.
Indicator, dedicated fixture or CMM referenced to the drawing-defined datum axis.
Optical system, CMM or pin-based method from specified datums.
Go/No-Go or functional gauges for class, fit and plating allowance.
Profilometer with the specified cutoff, direction and inspection stage.
Production Capability
One conforming part proves only a single result. Production capability requires a controlled process that remains stable across tools, time, operators and accepted lots.
Verify setup, datum interpretation and measurement conditions before releasing the run.
Record ballooned characteristics, CTQs, agreed methods and acceptance results.
Set inspection frequency from functional risk, process history and expected drift.
Trend offsets and CTQs; define correction or tool-change limits before nonconformance.
Calculate Cp or Cpk only after measurement-system validation, stable conditions and sufficient production data.
Process Boundary
Swiss turning can establish datums and near-net geometry, but selected CTQs may require a controlled finishing operation after turning or treatment.
Grinding may be required when turning variation leaves too little process margin for a selected CTQ diameter.
Bearing, sealing or sliding surfaces may require grinding, honing or polishing, depending on geometry and function.
Heat treatment, plating or coating can shift size, roundness and finish. Define the condition used for final acceptance.
Tolerance-Ready RFQ
A complete RFQ lets engineering review tolerances against the planned manufacturing and verification route. Missing datums, process stage or inspection details can make pricing provisional.
Show tolerances, GD&T, notes and revision status.
Provide nominal geometry and feature-access context.
State grade, temper, hardness and stock restrictions.
List order size, annual volume, lot size and delivery schedule.
Identify the axes and faces that establish acceptance.
Separate critical features from general dimensions.
Define heat treatment, coating and final-size responsibility.
Specify first-off or FAI, sampling frequency, reports and gauges.
Tolerance FAQ
Concise answers to common Swiss CNC tolerance questions. Final acceptance depends on the controlled drawing, feature relationships, process stage and agreed measurement conditions.
No. Selected CTQs may be reviewed to ±0.005 mm, but capability depends on geometry, material, support, tooling, thermal stability, datums and the approved inspection method.
Do not assume it. Selected features may require grinding or controlled finishing, particularly after heat treatment or when very low roughness and stable geometry are required.
No. One setup reduces datum-transfer risk, but support, spindle condition, cutting force, feature sequence and measurement alignment still affect runout and coaxial relationships. Define the datum, control and acceptance method.
State the acceptance stage on the drawing. Heat treatment and coating can change size, form and surface condition; define the machining allowance and final inspection responsibility.
Match the method to the CTQ and feature access. Options include micrometers, optical systems, CMMs, profilometers, functional gauges and appropriate air or laser gauging.
Drawing-Based Engineering Review
Send the controlled 2D drawing and 3D CAD with material, quantity and named CTQs. We will confirm the machining route, inspection method and any required secondary finishing before quotation or production.
Confidential drawings and CAD files accepted.