A well-written rubber gasket RFQ saves time, reduces samples and prevents the most common cause of rework: missing dimensions. This guide shows how to specify rubber gasket dimensions, material, hardness, tolerances and flange details so the supplier can quote accurately the first time.
Minimum Information for Any Gasket RFQ
At minimum, include these eight items:
- Inner diameter (ID) and outer diameter (OD) — or the gasket outline if it is not a simple ring.
- Thickness — the uncompressed gasket thickness, not the groove depth.
- Material — EPDM, NBR, VMQ silicone, CR neoprene, FKM or PTFE.
- Hardness — Shore A durometer, e.g. 70 Shore A.
- Quantity — per order and annual estimate.
- Application — fluid, temperature and pressure.
- Cut method or tolerance — die-cut, flashcut, waterjet, laser, or molded.
- Drawing format — DXF, PDF or STEP.
Missing any one of these usually forces the supplier to ask follow-up questions, delaying the quote by one or more days.
Gasket Profile Types
Ring gasket
A simple flat ring with an ID and OD. Used on raised-face flanges where the gasket sits inside the bolt circle and seals against the raised flange face.
- Dimensions needed: ID, OD, thickness
- Bolt holes: not required in the gasket (bolts pass outside the OD)
- Common standards: ASME B16.21 ring gaskets for raised-face flanges
Full-face gasket
A flat gasket that extends to the outer edge of the flange and includes bolt holes. Used on flat-face flanges, cast iron flanges, and plastic flanges where the gasket helps align the bolts and distribute bolt load.
- Dimensions needed: ID, OD, thickness, bolt circle diameter (BCD), bolt hole diameter, number of bolt holes
- Bolt hole pattern must match the flange exactly
- Common standards: ASME B16.21 full-face gaskets
Custom profile gasket
Any gasket with a non-circular outline, cutouts, notches, ribs, lips, or bonded metal inserts. Common in equipment covers, valve bodies, pumps, and filters.
- Dimensions needed: complete 2D outline, thickness, all cutouts, locating features, tolerances
- Preferred file: DXF with a single closed polyline per gasket
Gasket Drawing Best Practices
A good gasket drawing shows ID, OD, thickness, bolt-hole locations (for full-face flanges), and any cutouts or notches. If the gasket matches a flange standard such as ASME B16.21, state the nominal pipe size and pressure class rather than drawing every dimension from scratch.
For custom profiles, send a DXF file with a single closed polyline per gasket. Remove dimensions and title blocks from the cutting layer to avoid translation errors.
Drawing checklist
| Feature | Required? | Notes |
|---|---|---|
| ID and OD | Yes | For ring and full-face gaskets |
| Thickness | Yes | Uncompressed thickness |
| Bolt circle diameter (BCD) | For full-face | Centerline of bolt holes |
| Bolt hole diameter | For full-face | Usually bolt diameter + 1.5–3 mm clearance |
| Number of bolt holes | For full-face | Must match flange |
| Material callout | Yes | Include grade if known |
| Hardness | Yes | Shore A durometer |
| Tolerance | Recommended | Default to cut-method tolerance if not specified |
| Surface finish | Optional | Usually not critical for rubber gaskets |
| Special features | If applicable | Ribs, lips, adhesive backing, metal inserts |
Gasket Tolerance Guidelines
Tolerances depend on cut method:
| Cut Method | Typical Tolerance | Best For | Notes |
|---|---|---|---|
| Die-cut | ±0.1–0.2 mm | High-volume production | Tooling required; tightest tolerance |
| Flashcut (CNC knife) | ±0.1–0.3 mm | Prototypes and low volumes | No hard tooling; good for soft materials |
| Waterjet | ±0.2–0.5 mm | Thick or hard materials | Can cut stacked sheets; wider kerf |
| Laser | ±0.1–0.3 mm | Thin sheets and fine details | Heat-affected edge on some materials |
| Molded | ±0.2–0.5 mm | Complex 3D profiles | Tooling required; best for high volume |
Tighter tolerances increase cost. Specify only what the joint actually needs. For most static flanges, ±0.3 mm is adequate.
Material Selection Guide
Match the material to the media first, then choose hardness.
| Material | Best For | Avoid | Typical Hardness | Temperature Range |
|---|---|---|---|---|
| EPDM | Water, steam, glycol, ketones, weathering | Petroleum oils, fuels, solvents | 50–80 Shore A | −50°C to +150°C |
| NBR | Petroleum oil, hydraulic fluid, diesel, aliphatic fuels | Ozone, ketones, esters, aromatics | 40–90 Shore A | −40°C to +120°C |
| HNBR | Oil, fuel, sour gas, high-temp oil service | Ketones, strong acids | 70–90 Shore A | −30°C to +150°C |
| FKM | High-temp oil, fuel, aromatics, acids | Steam, hot water, ketones, amines | 50–90 Shore A | −20°C to +200°C |
| VMQ (silicone) | Food, medical, dry heat, wide temp swings | Petroleum oils, high-pressure hydraulics | 30–80 Shore A | −60°C to +230°C |
| CR (neoprene) | Refrigerants, weathering, moderate oil | Aromatic fuels, strong oxidizers | 50–80 Shore A | −40°C to +120°C |
| PTFE | Aggressive chemicals, high temp, cryogenics | Dynamic service without energization | N/A (thermoplastic) | −200°C to +260°C |
For food-contact gaskets, specify FDA-compliant grades. For potable water, specify NSF 61 or WRAS compliance as required.
Hardness Selection
A 70 Shore A compound is the default for most industrial flanges. Use softer grades for rough surfaces and harder grades for high pressure or small extrusion gaps.
| Hardness | Typical Use |
|---|---|
| 40–50 Shore A | Low bolt load, rough surfaces, fragile flanges |
| 60–70 Shore A | General-purpose static flanges |
| 70 Shore A | Default for most industrial gaskets |
| 80–90 Shore A | High pressure, small extrusion gaps, reinforced materials |
For high-pressure applications, harder gaskets resist blowout but require smoother flange surfaces and higher bolt load to seal.
Flange Class and Bolt Pattern
For pipe flange gaskets, include the flange standard (ASME B16.21, DIN EN 12560), nominal pipe size and pressure class. For full-face gaskets, the bolt-hole pattern must match the flange exactly. For ring gaskets, only the ID/OD and thickness matter as long as the OD clears the bolts and the ID covers the bore.
Common flange gasket standards
| Standard | Region | Gasket Type |
|---|---|---|
| ASME B16.21 | North America | Non-metallic flat gaskets for pipe flanges |
| DIN EN 12560 | Europe | Flange gaskets for PN-designated flanges |
| JIS B 2404 | Japan | Rubber gaskets for pipe flanges |
| BS 3063 | UK | Dimensions for circular gaskets |
When quoting a standard flange gasket, provide:
- Nominal pipe size (NPS or DN)
- Pressure class (e.g., ASME Class 150, PN16)
- Flange facing type (raised face, flat face, tongue-and-groove)
- Material and hardness
Bolt torque
Bolt torque is not needed for quoting, but it is useful for design review. Torque depends on gasket material, thickness, flange size, and required compressive stress. Typical target compressive stress for rubber gaskets:
- Soft rubber (50 Shore A): 1–3 MPa
- Medium rubber (70 Shore A): 3–6 MPa
- Hard rubber (90 Shore A): 6–10 MPa
If you are unsure, our engineers can recommend torque based on gasket material, thickness and flange size.
Common RFQ Mistakes
- Sending a photo without dimensions.
- Confusing groove depth with gasket thickness.
- Omitting the fluid or temperature.
- Requesting die-cut tolerances on a waterjet prototype.
- Reusing an old drawing that no longer matches the flange.
- Specifying a material that is incompatible with the media.
- Forgetting to include bolt-hole pattern for full-face gaskets.
Gasket Sizing for Common Flange Types
Raised-face flange
Use a ring gasket. The OD should be slightly smaller than the bolt circle diameter so the gasket does not interfere with the bolts. The ID should match or slightly exceed the pipe bore to avoid flow restriction.
Flat-face flange
Use a full-face gasket. The gasket extends beyond the bolt circle and includes bolt holes. This distributes bolt load across the flange and prevents the gasket from shifting during assembly.
Tongue-and-groove flange
The gasket is trapped in a groove and compressed by a matching tongue. Dimensions must match the groove exactly. Specify groove width, depth, and diameter so the supplier can confirm fit.
Prototyping and Sampling
For prototype quantities (1–10 pieces), waterjet or flashcut is usually fastest and avoids tooling cost. For production volumes above ~500 pieces, die-cutting becomes cost-effective. Molded gaskets are economical only at high volumes with complex profiles.
| Volume | Recommended Method | Typical Lead Time |
|---|---|---|
| 1–10 | Waterjet / flashcut | 3–7 days |
| 10–500 | Flashcut / small die | 5–10 days |
| 500–10,000 | Die-cut | 10–20 days (includes tooling) |
| 10,000+ | Die-cut or molded | 15–30 days |
Submitting the RFQ
Upload your drawing and specification to our custom rubber gasket quote page or use the general request a quote form. We respond within 24 hours with material recommendation, cut method, tooling cost and lead time.
FAQ
Q1: What is the most common information missing from a gasket RFQ?
The operating fluid and temperature. Without them, the supplier cannot confirm material compatibility, which is the leading cause of gasket failure.
Q2: Can I quote a gasket from a physical sample instead of a drawing?
Yes. Mail the sample or send high-resolution photos with a ruler for scale. We can reverse-engineer ID, OD and thickness, but material identification may require testing if it is not marked.
Q3: What tolerance should I specify for a prototype gasket?
Use waterjet or flashcut tolerances of ±0.2–0.5 mm for prototypes. Die-cut tolerances are only achievable after tooling is made.
Q4: How do I know if I need a full-face or ring gasket?
Full-face gaskets suit flat-face flanges and softer materials like cast iron or plastic. Ring gaskets suit raised-face steel flanges. Match the gasket profile to the flange facing.
Q5: Should I include bolt torque in the RFQ?
Bolt torque is not needed for quoting, but it is useful for design review. If you are unsure, our engineers can recommend torque based on gasket material, thickness and flange size.
Q6: What file format is best for gasket drawings?
DXF is preferred for 2D cutting because it defines the exact path the cutter follows. PDF is acceptable for review but not for programming cutting equipment. STEP or IGES are needed for 3D molded profiles.
Q7: How do I choose gasket thickness?
Gasket thickness should match the flange gap in the assembled condition. Common thicknesses are 1.5 mm, 2 mm, 3 mm, and 5 mm. Thicker gaskets conform better to rough flanges but require higher bolt load. Thinner gaskets provide better blowout resistance but need smoother flanges.
Q8: Can rubber gaskets be used with hydrocarbon fuels?
NBR and FKM are the standard choices for fuel service. EPDM, VMQ, and CR are generally not compatible with hydrocarbon fuels. For aromatics or high temperatures, specify FKM.
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