Product Overview
Reliable custom rubber parts for industrial applications
Quick Answer
This square rubber flat gasket is designed for static sealing, cushioning, dust protection and surface isolation in covers, housings, panels, flanges and machinery assemblies. Length, width, thickness, hole pattern, material, Shore A hardness, color, tolerance and packaging can be customized according to the drawing or physical sample.
A square rubber flat gasket is a flat elastomer sealing component used between compatible mating surfaces in covers, housings, panels, flanges and machinery assemblies. It helps reduce leakage, vibration transfer, dust entry and surface damage under controlled compression. Dimensions, thickness, rubber compound, Shore A hardness, hole pattern and tolerance can be customized according to the drawing or sample.
Product Overview
The square rubber flat gasket is designed for static sealing and cushioning between flat or lightly compressed surfaces. Its square shape makes it suitable for equipment covers, inspection plates, electrical enclosures, pump housings, valve bodies, mounting pads and non-circular flange interfaces. Depending on the application, the gasket can be supplied as a solid square pad, a square gasket with a central opening, or a square gasket with bolt holes. The flat profile helps distribute compression across the sealing area and can compensate for minor surface irregularities. Material selection depends on temperature, contact media, pressure, outdoor exposure, compression set and dimensional tolerance requirements.
| Attribute | Value |
|---|---|
| Part Name | Square Rubber Flat Gasket with Center Bore |
| Also Known As | Square Face Seal Gasket / 4-Bolt Square Port Gasket / Square Flange Seal / Rectangular Equipment Gasket |
| Shape | Square with radiused corners; circular center bore; 4 bolt holes at corners |
| Materials Available | NBR, EPDM, HNBR, FKM (Viton®), VMQ (Silicone), CR (Neoprene), NR, Butyl |
| Color | Black (standard); other colors by compound |
| Hardness Range | Shore A 40–80 (standard: 60A or 70A) |
| Size Range | 30×30 mm to 200×200 mm standard; custom larger sizes on request |
| Center Bore Range | 10 mm to 120 mm (matched to port bore) |
| Thickness | 1.5 mm, 2.0 mm, 3.0 mm, 4.5 mm, 6.0 mm standard |
| Temperature Range | -60°C to +250°C (compound-dependent) |
| Pressure Rating | Up to 400 bar (compound, thickness, and bolt pattern dependent) |
| Fabrication | Die-cut, water-jet cut, compression moulded |
| Certifications | RoHS, REACH; FDA (VMQ/EPDM); WRAS (EPDM) |
Key Features
- Square flat gasket structure for static sealing, cushioning and surface protection.
- Suitable for covers, housings, panels, flanges, enclosures and machinery interfaces.
- Can be supplied as solid, center-cut, bolt-hole or custom-shaped gasket designs.
- Dimensions, thickness, hole pattern and edge profile can be customized to drawing.
- Material selection can be reviewed for water, oil, air, dust, weather or chemical exposure.
- Shore A hardness can be selected according to compression and sealing requirements.
- Die cutting, water-jet cutting or rubber molding can be used according to quantity and tolerance.
- Samples, inspection requirements and custom packaging are available upon request.
Product Specifications
| Specification | Details |
|---|---|
| Product Name | Square Rubber Flat Gasket |
| Material | EPDM, NBR, CR, Silicone, FKM, NR, SBR or application-specific rubber compound |
| Hardness | Available upon request |
| Color | Black or custom color, depending on the selected compound |
| Manufacturing Process | Die cutting, water-jet cutting, compression molding or injection molding, depending on gasket structure and quantity |
| Application | Static sealing, cushioning, dust protection, vibration isolation and surface protection between compatible flat interfaces |
| Customization | Length, width, thickness, central opening, hole diameter, hole spacing, material, Shore A hardness, color, surface finish, dimensional tolerance, packaging and inspection requirements can be reviewed according to the drawing. |
| MOQ | Contact us for details |
| Tooling | Tooling cost depends on the drawing and product structure |
| Sample Availability | Available upon request |
| Lead Time | Available upon request |
| Compliance Options | RoHS, REACH, FDA and other material documentation options are available upon request for applicable compounds. |
Material Selection Guide
NBR — Nitrile Butadiene Rubber (Primary Compound for Hydraulic & Oil Service)
NBR is the standard compound for square gaskets in hydraulic valve block and manifold applications — the largest application market for this gasket type. NBR’s outstanding resistance to mineral hydraulic oil, petroleum-based lubricants, fuel, and greases makes it the default specification for any square-port connection in an oil-wetted or hydraulic system. Carbon-black reinforced NBR in 60A–70A hardness provides the combination of oil swell resistance, dimensional stability under sustained compression, and mechanical strength required for high-cycle hydraulic service.
- Mineral hydraulic oil, lubricating oil, gear oil
- Diesel, petrol, kerosene fuel systems
- Natural gas (dry) equipment connections
- General industrial oil-contact service
- Temperature: -40°C to +100°C |
- Hardness: Shore A 55–75
EPDM — Ethylene Propylene Diene Monomer (Water, Steam & Outdoor Service)
EPDM square gaskets are the standard choice for water-service equipment, HVAC system components, and any application where outdoor weathering or UV exposure is a factor. EPDM does not degrade, crack, or harden in outdoor atmospheric exposure — a critical advantage for equipment installed externally. WRAS-approved EPDM compound is available for potable water compliance.
- Cold water, hot water, steam service
- HVAC chilled water and heating equipment
- Outdoor and UV-exposed installations
- Water treatment equipment flanges
- Temperature: -50°C to +150°C |
- Hardness: Shore A 55–70
HNBR — Hydrogenated Nitrile Butadiene Rubber (Hot Oil & Elevated Temperature)
HNBR extends the temperature ceiling of NBR from +100°C to +150°C while maintaining equivalent oil resistance, making it the specified compound for hot oil equipment connections, high-temperature hydraulic systems, and oilfield equipment operating above NBR’s temperature limit.
- Hot oil, transmission fluid, engine coolant circuits
- High-temperature hydraulic systems
- Oilfield and refinery equipment
- Temperature: -40°C to +150°C |
- Hardness: Shore A 60–75
FKM — Fluoroelastomer (Viton®) (Chemical Resistance & High Temperature)
FKM square gaskets are specified wherever the media aggressiveness or operating temperature exceeds the capability of NBR or EPDM. FKM resists concentrated acids, aromatic solvents, chlorinated solvents, aggressive fuels, and high-temperature process fluids — the broadest chemical resistance spectrum of any standard elastomeric gasket material.
- Chemical process equipment connections
- Aggressive fuel and solvent systems
- High-temperature oil service above +150°C
- Aerospace and defense hydraulic systems
- Temperature: -20°C to +200°C
- Hardness: Shore A 60–80
VMQ — Silicone Rubber (Food, Pharma & Extreme Temperature)
VMQ silicone square gaskets operate from -60°C to +250°C and are the only compound that remains elastic and functional at cryogenic temperatures. FDA-grade VMQ is mandatory for food, beverage, and pharmaceutical process equipment connections.
- Food and beverage processing equipment
- Pharmaceutical and biotech systems
- Autoclave and steam sterilization connections
- Cryogenic and extreme-temperature applications
- Temperature: -60°C to +250°C
- Hardness: Shore A 40–70
CR — Chloroprene (Neoprene) (Marine & Moderate Oil + Weather Resistance)
CR provides the combination of moderate oil resistance and outstanding outdoor weathering resistance not available from either EPDM (poor oil resistance) or NBR (poor weathering resistance), making it the choice for marine equipment, outdoor installations, and mixed oil-and-weather exposure applications.
- Marine and offshore equipment connections
- Outdoor plant and equipment
- Refrigerant service (moderate)
- Temperature: -40°C to +120°C
- Hardness: Shore A 50–70
Compound Selection Matrix
| Media | Temp Range | Best Compound |
|---|---|---|
| Mineral oil, hydraulic oil, diesel | ≤ +100°C | NBR |
| Hot oil, oilfield fluids | ≤ +150°C | HNBR |
| Aggressive chemicals, solvents | ≤ +200°C | FKM |
| Water, steam, HVAC, outdoor | ≤ +150°C | EPDM |
| Food, pharma, FDA contact | -60°C to +250°C | FDA VMQ |
| Gas pipeline, low permeability | ≤ +130°C | Butyl (IIR) |
| Marine, moderate oil + UV | ≤ +120°C | CR |
Standard Size Series
| Size Code | Outer (L×W) | Center Bore | Bolt Hole Dia. | Thickness | Typical Port Size |
|---|---|---|---|---|---|
| SQ-30 | 30 × 30 mm | 12 mm | 5 mm | 2.0 mm | DN10 / 3/8″ |
| SQ-40 | 40 × 40 mm | 20 mm | 6 mm | 2.0 mm | DN15 / 1/2″ |
| SQ-50 | 50 × 50 mm | 26 mm | 7 mm | 2.0 mm | DN20 / 3/4″ |
| SQ-60 | 60 × 60 mm | 33 mm | 8 mm | 3.0 mm | DN25 / 1″ |
| SQ-70 | 70 × 70 mm | 40 mm | 8 mm | 3.0 mm | DN32 / 1¼” |
| SQ-80 | 80 × 80 mm | 48 mm | 10 mm | 3.0 mm | DN40 / 1½” |
| SQ-95 | 95 × 95 mm | 58 mm | 10 mm | 3.0 mm | DN50 / 2″ |
| SQ-115 | 115 × 115 mm | 70 mm | 12 mm | 4.5 mm | DN65 / 2½” |
| SQ-130 | 130 × 130 mm | 85 mm | 12 mm | 4.5 mm | DN80 / 3″ |
| SQ-155 | 155 × 155 mm | 105 mm | 14 mm | 4.5 mm | DN100 / 4″ |
| SQ-185 | 185 × 185 mm | 130 mm | 14 mm | 6.0 mm | DN125 / 5″ |
| SQ-210 | 210 × 210 mm | 155 mm | 16 mm | 6.0 mm | DN150 / 6″ |
Thickness Selection Guide
| Thickness | Application |
|---|---|
| 1.5 mm | Precision-machined faces, high bolt load, instrument-scale ports |
| 2.0 mm | Small bore (SQ-30 to SQ-50), standard machined equipment faces |
| 3.0 mm | General industrial — most common for equipment flanges SQ-60 to SQ-115 |
| 4.5 mm | Larger bores, moderate surface finish, lower bolt load applications |
| 6.0 mm | Large equipment flanges, rough cast surfaces, vibration-exposed connections |
Fabrication Methods
Die-Cutting
The standard production method for high-volume orders in standard sizes. A matched hardened steel tool — outer square profile, center bore punch, and corner bolt hole punches — cuts the complete gasket profile from rubber sheet in a single press operation. Die-cutting delivers consistent dimensions and clean edges at the lowest per-piece cost for volumes above 500 pieces per size. Corner radii are incorporated into the tooling for smooth, stress-free corners.
Water-Jet Cutting
No tooling required. A CNC-controlled water-jet cuts any square, rectangular, or custom profile directly from rubber sheet guided by a DXF file. Water-jet cutting is the production method for non-standard sizes, prototype gaskets, urgent replacement parts for legacy equipment, and first-article samples before committing to die tooling. Typical lead time 3–5 working days from dimension file receipt.
Compression Moulding
For applications requiring the tightest dimensional tolerances, controlled compound properties, FDA compliance, or design features (such as integrated sealing beads or locating features) not achievable by cutting from sheet, compression moulding in a hardened precision tool delivers superior performance. Lead time 4–6 weeks for tooling plus first article, then standard production from stock tooling.
Primary Application Markets
Hydraulic Manifold Blocks & Valve Bodies
The highest-volume application for square rubber gaskets worldwide. Hydraulic manifold blocks — machined from solid aluminum or ductile iron — have square ported faces on all six sides where hydraulic valves, actuators, transducers, and pipe connections bolt directly to the manifold. Each bolted connection requires a square rubber gasket sized precisely to the port bore and bolt circle. NBR 70A is the near-universal compound specification for hydraulic manifold port sealing. The gasket must resist continuous mineral hydraulic oil immersion, maintain dimensional stability under sustained bolt pre-load, and provide reliable sealing up to the system proof pressure.
Pneumatic Cylinder End Caps
Pneumatic cylinders have square or rectangular aluminum end caps bolted to the cylinder bore. The end cap gasket seals the pneumatic circuit at each end of the cylinder, preventing compressed air leakage. NBR and EPDM are both used — NBR where compressor oil contamination is present in the air supply; EPDM for clean dry air applications. The gasket must maintain sealing through millions of pneumatic actuation cycles without significant compression set.
Industrial Pump Square Flanges
Gear pumps, vane pumps, and positive displacement pumps frequently have square bolted end covers and port connections. Square rubber gaskets seal both the main end covers (containing the shaft seal region) and the inlet/outlet port connections. NBR is standard for oil-lubricated pumps; EPDM for water pumps; FKM for chemical-service pumps.
Industrial Equipment Inspection Covers & Access Ports
Gearboxes, hydraulic reservoirs, gear cases, and industrial process vessels have bolted square access covers and inspection ports. The gasket seals the cover against the machined face of the housing, preventing oil or fluid leakage. NBR for oil-wetted housings; EPDM for water or outdoor-exposed housings.
EDM (Electrical Discharge Machining) Work Tanks
EDM machine work tanks have multiple square and rectangular port connections for dielectric fluid circulation, filtration, and drainage. NBR rubber square gaskets seal these port connections against the dielectric fluid (petroleum-based or deionized water-based) used in the EDM process.
Custom OEM Equipment Interfaces
Any OEM equipment with square or rectangular bolted interfaces — medical devices, laboratory equipment, analytical instruments, semiconductor process equipment, food processing machinery — can be sealed with a custom square rubber gasket dimensioned precisely to the equipment interface drawing. VMQ (silicone) for food, medical, and high-temperature applications; FKM for chemical process equipment; EPDM for water-contact and outdoor-exposed equipment.
Quality & Compliance
| Test / Standard | Method | Specification |
|---|---|---|
| Hardness | ISO 48-4 / ASTM D2240 | Shore A ± 5 of specified value |
| Tensile Strength | ISO 37 / ASTM D412 | ≥ 7 MPa |
| Elongation at Break | ISO 37 | ≥ 200% |
| Compression Set | ISO 815 / ASTM D395B | ≤ 25% (22h @ 70°C) |
| Oil Resistance | ISO 1817 (IRM 903 oil, 70h @ 100°C) | ≤ +25% volume change (NBR) |
| Ozone Resistance | ISO 1431-1 | No cracking (EPDM, CR) |
| Heat Aging | ISO 188 / ASTM D573 (70h @ 100°C) | ≤ ±15% property change |
| FDA Compliance | 21 CFR 177.2600 | Available for VMQ and EPDM |
| WRAS Approval | Water Regulations Advisory Scheme | Available for EPDM compound |
| RoHS / REACH | EU 2011/65/EU, 1907/2006 | All standard compounds compliant |
| Dimensional | Per customer drawing or standard | 100% OD, ID, bolt holes, thickness |
| Material Certificate | EN 10204 Type 2.1 | Supplied on request |
Installation Best Practices
- Do not reuse compressed gaskets — once removed, compression set prevents restoration of original sealing contact stress
- Clean both mating faces — remove all residue from previous gasket, machining oils, and surface contamination; contamination prevents uniform compression
- Inspect mating faces — check for scratches, tool marks, and corrosion; minor irregularities are accommodated by rubber deformation, but deep damage requires face rework
- Align center bore with port bore — slide the gasket over locating pins or into position with center bore centered on the port
- Insert all bolts before torquing — hand-tighten all four bolts finger-tight before applying torque to prevent gasket shifting
- Tighten in diagonal cross sequence — bolt 1 (top-left) → bolt 3 (bottom-right) → bolt 2 (top-right) → bolt 4 (bottom-left); this maintains even compression across the gasket
- Apply torque in three passes — 30% → 70% → 100% of specified torque, repeating cross sequence each pass
- Final circular check pass — after three cross-sequence passes, make one final clockwise pass to equalize
- Re-torque after first pressurization — rubber relaxes under initial load; re-torque to target after first system pressurization and, where applicable, first thermal cycle
Customization Options
Custom square rubber flat gaskets can be produced from 2D drawings, CAD files, dimensional sketches or physical samples. Buyers can specify length, width, thickness, corner radius, center opening, bolt-hole pattern, edge finish, material, Shore A hardness, color and tolerance. Flat gaskets can often be die-cut or water-jet cut from rubber sheet. Molded gaskets can be reviewed when a raised lip, recessed section, groove-fit structure or tighter geometry control is required. Please provide operating temperature, contact media, pressure or compression conditions, application environment and estimated annual demand for material and process review.
FAQ
What is a square rubber flat gasket used for?
A square rubber flat gasket is used for static sealing, cushioning and surface protection between compatible flat interfaces. It can be installed in covers, housings, panels, enclosures, valve plates and machinery assemblies where a square gasket shape matches the mating surface.
Can the size and hole pattern be customized?
Yes. Length, width, thickness, central opening, bolt-hole diameter, hole quantity and hole spacing can be customized according to a drawing or physical sample. Critical tolerances should be confirmed before production, especially for enclosure sealing and bolted equipment interfaces.
How should buyers select the rubber material?
Material selection depends on the contact media, temperature, compression load and environment. EPDM can be reviewed for water and outdoor exposure. NBR is suitable for oil contact. CR provides balanced general-purpose performance. Silicone and FKM can be evaluated for higher temperature or demanding media.
Which manufacturing process is suitable for square rubber flat gaskets?
Die cutting is commonly used for flat sheet gaskets in standard or high-volume production. Water-jet cutting is useful for prototypes and non-standard shapes. Compression or injection molding can be reviewed when the gasket requires a molded lip, special profile or tighter structure control.
Is a square rubber flat gasket suitable for waterproof enclosure sealing?
It can be used for enclosure sealing when the gasket material, thickness, compression rate and housing design are suitable. Buyers should confirm the enclosure groove, clamping method, surface finish, expected water exposure and any required sealing standard before finalizing the gasket design.
Are samples available before bulk production?
Samples are available upon request. Sample planning depends on the material, size, thickness, hardness, tolerance and manufacturing process. Please provide a drawing, CAD file or physical sample so the square rubber flat gasket can be reviewed before batch production.
Request a Custom Quote
Send your square rubber flat gasket drawing, CAD file, dimensional sketch or physical sample for technical review. Please include the length, width, thickness, hole pattern, material, hardness, operating temperature, contact media, compression conditions, quantity and packaging requirements so we can prepare a practical quotation.
