Third-Party Inspection
Dimensional and geometrical inspection
Size, form, orientation, location and runout verified against the drawing with methods whose uncertainty suits the tolerance.
01What the service involves
Dimensional inspection verifies that a part's features conform to the drawing. Geometrical inspection extends this to form (flatness, roundness), orientation (parallelism, perpendicularity), location (position, concentricity) and runout, as defined by GD&T according to ISO GPS or ASME Y14.5.
QUALITAS TR performs dimensional inspection with hand instruments and gauges, witnesses and reviews CMM programmes and reports, and coordinates laser tracker or 3D scanning measurement for large or freeform parts. We also support reverse engineering measurement where drawings are missing.
02Why buyers need it
Dimensional nonconformities are the most common reason for rejection of machined, fabricated and cast parts. Many are not dimension errors but interpretation errors: wrong datum set-up, wrong treatment of material condition modifiers, or general tolerance misunderstanding.
Independent dimensional verification catches both, and confirms that the supplier's measurement method is fit for the tolerance.
03Typical applications
- Precision machined components
- Castings and forgings after machining
- Welded frames and structures
- Sheet metal assemblies
- Moulded plastic parts
- Large components requiring laser tracker measurement
04Methodology
Drawing analysis
Datums, feature control frames, modifiers and general tolerances identified; measurement plan prepared.
Method selection
Instrument chosen so that measurement uncertainty is small relative to tolerance.
Set-up check
Datum alignment and fixturing verified, especially for CMM measurement.
Measurement
Characteristics measured and recorded with actual values.
Evaluation
Results compared with limits; borderline results assessed considering uncertainty.
Process capability: Cp and Cpk
Specification 10.00 ±0.05 mm. Move the process mean and spread to see how capability changes.
Cp compares tolerance width with process spread; Cpk also accounts for centring.
05Applicable standards and references
ISO 1101 defines geometrical tolerancing symbols and their interpretation in the ISO GPS system. ISO 2768 defines general tolerances for linear and angular dimensions and for geometrical characteristics where drawings refer to it. Measurement system suitability is assessed using MSA principles.
06Deliverables
- Dimensional report with actual values
- Ballooned drawing
- CMM report review comments
- Out of tolerance list with deviations
- Measurement method and equipment record
07Customer benefits
- Correct interpretation of GD&T
- Confidence in supplier measurement results
- Fewer assembly problems at destination
- Objective data for concessions
- Early feedback on process capability
08How QUALITAS TR supports you
Dimensional inspection is a daily discipline for our engineers. Use the tolerance calculator to check limits and deviation for any toleranced dimension.
Frequently asked questions
Do you have your own CMM?
No. We witness and review CMM measurement at the supplier or coordinate measurement at independent metrology providers. Hand instruments and gauges for routine checks are our own and calibrated.
Can you measure large structures?
Yes, by coordinating laser tracker or photogrammetry measurement with specialist providers and reviewing results against the drawing.