Engineering Guide
OUJI reviews tolerances according to part function, material, feature size, geometry, manufacturing sequence, finishing, quantity, and inspection requirements.
The values on this page are general guidance. Final capability is confirmed through drawing review before quotation and production.
General Guidance
A tighter tolerance is not automatically better. The correct tolerance supports fit, function, movement, sealing, alignment, or assembly without adding unnecessary manufacturing and inspection risk.
±0.10 mm unless otherwise specified and agreed
Non-critical lengths, widths, profiles, and standard machined features
A practical starting point for many custom machined parts
Around ±0.05 mm for suitable features after review
Assembly dimensions, hole spacing, controlled diameters, and interfaces
May need more controlled setup, tooling, and inspection
Down to ±0.01 mm for suitable features and processes
Critical fits, bearing locations, sealing features, and functional datums
Requires review of geometry, material, size, quantity, process, and inspection
Subject to project-specific feasibility review
Specialized precision interfaces and finishing-dependent features
May require added operations, controlled conditions, or specialist resources
These values are not blanket guarantees. A short turned diameter, thin wall, deep cavity, long shaft, large plate, and multi-setup feature do not carry the same manufacturing risk.
Engineering Factors
Achievable tolerance is a combined result of design, process, material, workholding, inspection, and production quantity.
Thin walls, deep cavities, long features, narrow slots, and complex datum relationships increase deformation and setup risk.
The same numerical tolerance has a different manufacturing meaning on a 10 mm feature and a 500 mm feature.
Metals and engineering plastics respond differently to heat, cutting force, residual stress, and clamping.
Every repositioning can add alignment error. Multi-setup relationships require clear datum planning.
Producing one acceptable part and maintaining the result across a batch are different manufacturing challenges.
Anodizing, plating, coating, heat treatment, and precision finishing may change final size or geometry.
Process Differences
Machining and sheet-metal dimensions should not be evaluated using the same assumptions. Choose a process for the main review points.
CNC Milling
Multiple setups, tool reach, deep pockets, thin walls, and datum transfers can influence milled-part accuracy.
CNC Turning
Controlled diameters depend on part length, wall thickness, material, tool wear, clamping, and secondary operations.
Sheet Metal
Thickness, bend allowance, springback, welding, coating, and assembly requirements influence sheet-metal accuracy.
Measurable Requirements
The inspection method should match the feature, tolerance, access, quantity, and required report. CMM inspection is one option, not an automatic requirement for every dimension.
View OUJI Quality AssuranceCaliper, micrometer, or height gauge
Micrometer, bore gauge, or pin gauge
Plug gauge, ring gauge, or agreed functional check
Height gauge, fixture, or CMM when required
Surface plate, indicator, fixture, or CMM
CMM or purpose-specific inspection when agreed
Roughness tester using the stated parameter and location
Before Quotation
OUJI coordinates manufacturability review, suitable manufacturing resources, finishing requirements, and inspection expectations before production is released.
Confirm what affects fit, movement, sealing, positioning, or assembly.
Review geometry, material, setup, quantity, finishing, and deformation.
Agree how the requirement will be accessed, measured, sampled, and reported.
Identify added setup, tooling, inspection, finishing, or third-party work.
Confirm drawing revision, accepted limits, inspection scope, and special conditions.
Tolerance questions should be resolved before production, not after the parts are completed.
Common Questions
These answers are practical starting points. The approved drawing and agreed inspection method remain the basis for production.
A general tolerance of ±0.10 mm may be used as an initial reference for many standard machined dimensions unless otherwise specified and agreed. Final capability depends on feature geometry, size, material, process, quantity, finishing, and inspection requirements.
A tolerance down to ±0.01 mm may be achievable for suitable features and processes after engineering review. It is not a default tolerance for every dimension, geometry, material, or production quantity.
Requirements tighter than ±0.01 mm need detailed review of geometry, material, process sequence, workholding, temperature, finishing, quantity, and inspection method. Specialized finishing or third-party inspection may be required.
No. The applicable general tolerance standard and class must be confirmed through the drawing, quotation, and engineering review. Customer notes and individually specified tolerances take priority.
No. Inspection scope depends on drawing complexity, tolerance, quantity, application, and customer requirements. Critical characteristics are identified during review. Full-dimensional inspection can be arranged when specifically requested and agreed.
Anodizing, plating, heat treatment, powder coating, grinding, and polishing may change final dimensions or surface condition. Critical features should be identified as pre-finish or post-finish requirements before production.
Engineering Review
Upload your drawing and identify what affects fit, movement, sealing, alignment, or assembly. OUJI will review manufacturing risk, finishing effects, and inspection requirements before production.
2D drawing, 3D model, revision, material, quantity, and finished condition.
Identify the mating component and the dimensions or relationships that protect function.
State the required measurement method, sampling plan, report, certificate, or approval process.
Clear tolerance priorities reduce manufacturing uncertainty without compromising part function.
