Updated: September 16, 2026 · Topic: how to measure custom rubber seal profile
Quick Answer
For a custom rubber seal, provide a clean perpendicular cross-section with overall width and height, every wall thickness, channel or flange size, bulb diameter, lip length and critical tolerances. Add material, hardness, color, length, joining method, application photos and annual quantity. A physical sample is useful, but dimensions and the mating-part geometry are still needed for reliable tooling review. Do not scale dimensions from a photo alone; confirm every quotation-critical dimension on the physical sample or a controlled drawing.
Measurement Checklist for a Custom Extruded Seal
| Dimension or input | What to record | Measurement note |
|---|---|---|
| Overall profile envelope | Maximum width and maximum height | Measure the relaxed cross-section, not a compressed installation |
| Walls, webs and lips | Each wall thickness, lip length and lip angle where functional | Mark which values are critical rather than applying tight tolerances everywhere |
| Bulb or sponge section | Outside width/height, wall and internal void position | Do not crush soft sponge with excessive measuring force |
| Channel or gripping section | Inside width/depth, opening, leg length and metal-carrier location | Also measure the mating flange thickness and edge condition |
| Mounting features | Adhesive width/location, slots, holes, clips or joints | Show the installation direction and contact surface |
| Assembly condition | Working gap, target contact, movement and available space | Record minimum and maximum values at several locations |
Key Selection Factors
| Factor | What to check | Why it matters |
|---|---|---|
| Cross-section | Overall width/height, walls, lips, bulbs and channels | Defines extrusion geometry |
| Mating part | Flange thickness, channel width and contact surface | Confirms fit and compression |
| Material | EPDM, silicone, PVC, TPE/TPV or required performance | Guides compound selection |
| Commercial data | Cut length or coil, quantity, packing and target timing | Supports accurate quotation |
How to Prepare and Measure the Sample
- Relax the sample: use an uncompressed, unstretched and undamaged section; do not measure it while installed around a corner.
- Make the section square: cut or photograph perpendicular to the profile length. Include one image with a ruler for scale, but use written dimensions for quotation.
- Measure gently: use a suitable caliper for solid sections. For soft sponge, avoid squeezing the profile because measuring force can reduce the reading.
- Measure the assembly: record the mating flange, groove, channel and working gap at several positions, including minimum and maximum values.
- Control the drawing: state millimetres or inches, drawing revision, critical dimensions and the intended installation direction.
- Validate before production: if new tooling is needed, review and approve the drawing first, then trial a produced sample on the actual assembly before bulk production release.
How Should Tolerances Be Specified?
ISO 3302-1:2014 specifies dimensional-tolerance classes and conformity methods for moulded, extruded and calendared solid rubber products. The standard is a useful reference for solid rubber extrusions, but the applicable class, measurement method and function-critical dimensions must still be agreed on the drawing. It does not replace assembly fit testing, and a soft sponge or composite profile may need a project-specific method.
Use tighter tolerances only where the dimension controls retention, compression, sealing contact or assembly clearance. Identify the datum or reference feature and the condition in which the part is measured.
Common Specification Mistakes
- Photographing the profile at an angle instead of square-on
- Measuring a compressed, stretched or damaged sample
- Leaving critical tolerances undefined
- Omitting the mating flange and working gap
RFQ Package: Minimum Information to Send
| Category | Information to include |
|---|---|
| Geometry | Dimensioned cross-section, units, revision, critical tolerances and installation direction |
| Mating assembly | Flange/groove/channel dimensions, working gap, movement and application photos |
| Material and service | Preferred material or required performance, hardness/density if known, color, temperature, fluids and weather exposure |
| Secondary operations | Adhesive, flocking, carrier, joining, holes, cut length or coil length |
| Commercial scope | Prototype quantity, first order, annual demand, packaging, destination and requested timing |
| Reference part, if replacing an existing seal | Uncompressed physical sample and existing part number when available |
A complete package allows the manufacturer to separate confirmed requirements from assumptions before tooling and sampling. Reference-part details apply when an existing seal is being replaced.
Related Onaseal Solution
Review custom rubber extrusion profile options, see Custom Rubber Extrusion Service, or send your drawing and target quantity for sample availability and engineering review.
Frequently Asked Questions
Can you quote from a photo only?
A photo helps identify the profile, but a dimensioned cross-section or physical sample is normally needed for an accurate custom quote.
What file formats can I send?
Common PDF, JPG and CAD drawings are useful. Include units and mark critical dimensions clearly.
Do I need to specify rubber hardness?
If known, include it. If unknown, describe the application and send a sample so the engineering team can recommend a starting point.