Legacy drawings may use T1–T4 or H-class language, but the label alone is not an acceptance table. Copy the nominal dimensions and numerical limits from the approved drawing and invoked standard edition, and assess any EN 10305 alternative as a formal substitution.
What does DIN 2391 cover beyond material grades?
A DIN 2391 callout must be read with its edition, product scope, material designation, delivery condition, dimensions, tolerances, testing, and documents. Do not reconstruct missing requirements from a supplier summary.
Start with the exact standard and edition named by the controlled drawing. Record the product form, material designation, delivery condition, dimensions, tolerances, surface condition, tests, and inspection-document requirements as separate fields.
A T-class or H-class label seen on a legacy drawing may depend on another table or dimensional system. Confirm the nominal size and actual upper and lower deviations rather than relying on a percentage or application mapping from this page.
Delivery-condition terms describe manufacturing history but do not by themselves establish weldability, formability, machining stability, bore finish, pressure suitability, or application. Those decisions belong to the approved material and process plan.
When a supplier proposes EN 10305 material against a DIN 2391 drawing, compare scope, grade properties, condition, dimensions, tolerances, testing, and documents line by line. An MTC and similar grade name do not automatically approve the substitution.
How do OD tolerance classes T1 through T4 differ in practice?
T1 through T4 are drawing and standard references for outside-diameter control. Confirm the applicable edition, ordered size, and millimetre limits on the approved drawing before using any class label.
The OD tolerance class determines how tightly the outside diameter is controlled, but a class name alone is not a complete purchase specification. Copy the class and numerical limit from the invoked standard or approved drawing for the ordered size.
Do not infer an application, price, or availability from a T1, T2, T3, or T4 label. Those commercial and engineering decisions depend on the drawing, mating parts, finishing route, offered mill capability, and current written quotation.
Where a legacy drawing uses DIN terminology and a supplier offers an EN 10305 alternative, compare the actual millimetre limits and obtain technical approval. Similar-looking class labels are not permission to substitute.
State the measurement method, acceptance limit, and inspection-document requirement on the RFQ when outside diameter is functional. The supplier should confirm the offered class and limits in writing.
What wall thickness tolerance applies to DIN 2391 precision tubes?
Wall thickness, outside diameter, finished bore, ovality, and straightness are separate acceptance fields. Copy each required limit from the approved drawing and invoked standard edition; do not infer a wall tolerance from an OD or bore class label.
A percentage, plus/minus value, or minimum finished wall belongs on the drawing or purchase specification. This page does not assign a generic value to an as-drawn, honed, H8, or H9 product.
The ordered condition and machining route can change which dimensions are functional and when they are measured. State whether acceptance applies before or after honing, skiving, machining, heat treatment, or coating.
For a cylinder barrel, list nominal OD, nominal ID or wall, minimum finished wall, permitted ovality, straightness, surface finish, and the required measurement report as separate fields. The designer and seal specification control the acceptance window.
Do not let a supplier replace one missing limit with a familiar class combination. Any proposed alternative should show the actual numerical limits and receive technical approval before the PO changes.
When should a buyer specify bore class E, H8, or H9?
Use the bore tolerance and finish named on the approved drawing. H8 and H9 are ISO tolerance-zone designations, not automatic application choices, and an as-drawn tube should not be treated as a finished sealing bore without explicit acceptance criteria.
A finished-bore designation must be read with its nominal diameter because the permitted deviation is size-dependent. Copy the actual limit from the invoked ISO table or approved drawing rather than using an approximate range from a supplier page.
State the manufacturing condition separately from the final-bore tolerance. As-drawn, honed, skived and roller-burnished, or buyer-machined describe different routes and cannot be substituted merely because a final class label looks similar.
For sealing duty, the cylinder designer and seal supplier should confirm diameter, surface finish, geometry, pressure, temperature, fluid, and wear requirements. Procurement then places those accepted values on the RFQ.
When an alternative H-class or finishing route is offered, require a dimensional comparison and technical approval. Price or lead-time preference is not an engineering acceptance criterion.
Which tolerance class combination suits different applications?
Copy the OD class, bore class, and delivery condition from the drawing. Do not treat T3+H8, T2+H9, or T4+NBK as universal application rules from this page.
For a hydraulic cylinder barrel, the drawing may control the finished bore, OD mounting surfaces, minimum wall, straightness, and finish independently. Copy those values; do not default to a T-class and H-class pair.
For driveshaft, CV-joint, bearing, guide, or piston-rod work, identify the functional surfaces, subsequent forging or machining, mating-component fits, and inspection stage. The application name alone does not select T1, T2, T3, T4, E, H8, or H9.
For pressure-containing parts, material, heat treatment, minimum finished wall, end construction, welding, fatigue, inspection, and the governing design code are part of the acceptance basis. A tight dimensional class does not establish pressure suitability.
Ask the engineering owner to approve a tolerance stack for the complete assembly. The RFQ should reproduce that controlled stack and require the offered numerical limits, not let a supplier choose from a generic application table.
What is the relationship between DIN 2391 and EN 10305 tolerance classes?
DIN 2391 and EN 10305 references must be compared by edition, product scope, grade, delivery condition, dimension, and numerical tolerance. Do not use a universal T1-to-E, T2-to-E1, T3-to-E2, or T4-to-E3 mapping from this page.
Legacy drawings and current quotations may use different standard references. Treat that as a controlled substitution question, not proof that the scope, grade, condition, or acceptance limits are equivalent.
Build a line-by-line comparison using the editions invoked by the drawing and offer. Check product type, steel designation, delivery condition, OD, ID or wall, tolerances, straightness, surface condition, testing, and inspection documents.
For procurement clarity, copy the approved standard, grade, tolerance class, delivery condition, and required inspection-document type. Treat any DIN-to-EN alternative as a formal technical substitution requiring approval, not as automatic equivalence wording.
Buyers should reject RFQ responses that cite only the old standard without confirming tolerance equivalence. A response reading "DIN 2391 ST52 BK" without tolerance class specification is incomplete. The correct response includes both the standard and the tolerance class together.
What does RP Sales normally stock, and what substitutions should buyers avoid?
Confirm on the written quotation which OD class, grade, delivery condition, and bore class are actually offered. Do not treat T3 / ST52 / BK+S / H8 as live stock, and do not substitute class names without comparing the millimetre limits on the drawing.
Availability is lot-specific. Confirm OD class, wall tolerance, grade, and delivery condition on the written quotation. Do not treat T3, ±10% wall, ST52/E355, or BK+S as a live stock combination.
Do not substitute a looser OD class for a named hydraulic class without comparing the millimetre limits on the drawing. Confirm the offered class on the written quotation.
Do not over-specify or relax a tolerance class from an application label. Ask engineering for the functional dimensions and limits, then require the quotation to confirm capability, price, and timing for that exact requirement.
When the ID is functional, a size string such as "100 x 90 tube" is incomplete. State the approved finished-bore dimension, tolerance, manufacturing condition, surface finish, geometry, and inspection method. Do not assume H8, H9, or an as-drawn condition from the word “hydraulic.”