Tolerance belongs to a feature and a function
A tolerance is meaningful only when it is connected to the way a feature fits, aligns, seals or moves in the assembly. Applying one tight value to an entire part can add cost without improving function.
Hongtao Metal can review requirements up to ±0.01 mm where geometry, material, datum strategy and machining conditions allow. This is not a default tolerance for every part or feature.
What affects achievable tolerance
The drawing value is only one part of the manufacturing problem.
- Part size, wall thickness and stiffness
- Material stability and heat introduced during machining
- Access to the feature and the number of setups
- Datum selection and relationships between machined faces
- Tool reach, workholding and surface-finish requirement
- Inspection method and environmental conditions
How to specify critical dimensions clearly
Use a controlled 2D drawing to identify datums, fits, geometric tolerances, threads and surface-finish requirements. Distinguish assembly-critical dimensions from general dimensions.
Before production, agree which dimensions require recorded inspection and whether a first article, sampling report or material certificate is required.
Frequently asked questions
Can every CNC feature be held to ±0.01 mm?
No. Feasibility depends on the feature, geometry, material, setup, datum scheme and inspection method. The requirement must be reviewed from the drawing.
Should I put tight tolerances on all dimensions?
Usually not. Tighten only the features that control fit, alignment, sealing or motion, and use practical general tolerances elsewhere.
Does the 3D model replace the 2D drawing?
The model is valuable for geometry review, but the 2D drawing should control tolerances, datums, threads, material and acceptance criteria.
When should inspection records be requested?
State the required dimensions, sampling level and report format during quotation so the inspection plan can be included before production starts.