Tolerances and GD&T
Make critical dimensions, datums and final-condition requirements clear before a tolerance becomes a production commitment.
Identify What Must Fit
Highlight the interfaces that control assembly, movement, sealing or tool function. Explain the consequence of variation where it is not obvious from the drawing. This helps focus the review on the characteristics that matter to your part, rather than treating every dimension as equally critical.
Keep the Drawing System Clear
Identify the drawing standard and edition that govern the requirements, where specified. ASME Y14.5 and ISO GPS requirements should not be mixed through undocumented assumptions. Keep the drawing notes, model and inspection expectations consistent, and raise conflicts before approval.
Explain the Datum Scheme
The datum references help define how geometric relationships are evaluated. Provide the mating context or functional setup where necessary, especially for plates, locating features, sliders or replacement inserts. A measured value is useful only when the evaluation matches the agreed requirement.
Review Capability by Feature
Tolerance feasibility depends on the feature, size, geometry, material condition, process route and inspection method. Request confirmation for the actual drawing. A tight tolerance achieved on one short feature does not establish the same capability on every surface of another part.
Define the Acceptance State
State whether each affected requirement applies before or after heat treatment, coating or polishing.
Identify protected surfaces, final fits and any allowed process allowance.
These decisions belong in the agreed manufacturing basis rather than an assumption made after parts have been finished.
Keep Deviations Visible
A proposed tolerance change is a request, not approval. Record the affected feature, reason and proposed requirement, and obtain the necessary design authorization before changing the production basis. Preserve the approved revision and acceptance criteria for subsequent orders.
Frequently Asked Questions
What is your standard machining tolerance?
Request a tolerance review for the actual drawing. A blanket number does not describe every feature, material and geometry, and should not replace a written quotation basis.
Should I supply a 2D drawing with a 3D model?
Provide both when the drawing contains tolerances, datums, finish or other requirements that are not fully represented in the model.
Does a general tolerance cover every feature?
Review the drawing notes and any individual requirements together. Special features or explicitly specified requirements may need separate interpretation.
Can a sample replace missing tolerance information?
A sample may support review, but it does not necessarily define the intended limits. This is especially important for worn replacement parts.
Can we inspect using the same setup?
For sensitive features, agree the datum establishment, support and measurement condition before production or initial approval.
Can the same tolerance apply to all three businesses?
Not automatically. Machined assembly parts, die components and mold components have different functional and inspection requirements.
Can you work from either ASME or ISO-based drawings?
Identify the required standard and edition and request confirmation during review. Do not assume that conventions can be substituted without checking the actual requirements.
How are coating-affected fits handled?
Identify the final fit and the state in which it is accepted. Masking, allowance or additional work must be agreed in the manufacturing scope.
How do I request a tolerance change?
Identify the drawing revision and affected feature, state the proposed change and obtain the necessary written design approval before implementation.
What should I highlight for a fast technical review?
Identify critical fits, geometric relationships, final-condition requirements and any feature for which the measurement method needs agreement.
Discuss Your Requirements
Share your part type, current drawing revision and the question you need to resolve. Include the quantity and delivery destination when a quotation is required.