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Beveled Washers
A comprehensive engineering reference for structural engineers, piping engineers, procurement teams and site supervisors — covering the critical function of beveled washers in compensating for sloped bearing surfaces on I-beam and channel flanges, pipe flanges with tapered faces, and inclined structural connections. Covering standard bevel angles, AISC and ASME requirements, material grades, dimensional data and quality documentation for all structural and process piping beveled washer applications.
Beveled Washer Function, Bevel Geometry
& Engineering Principles
Structural I-Beam · Pipe Flange · Bending Stress
Why Beveled Washers Are Critical
A beveled washer (also called a taper washer or slope washer) is a washer with one flat face and one inclined face, with the inclination angle matched to the slope of the surface against which the bolt head or nut must bear. When a bolt or nut bears against an inclined surface without a compensating beveled washer, the bolt is subjected to bending stress in addition to the intended tensile preload stress. This bending stress can be significant: for a standard M24 A325 bolt bearing on an I-beam flange with a 1:14.5 taper without a beveled washer, the induced bending stress at the thread root can equal or exceed 30–50% of the tensile preload stress — dramatically reducing the effective fatigue life of the bolt and increasing the risk of bolt fracture under cyclic loading.
The two most common applications requiring beveled washers are: (1) Structural I-beam and H-section connections, where the inner face of the beam flange is tapered (typically 1:14.5 gradient, equivalent to approximately 5°) due to the rolling taper of the flange; and (2) ASME pipe flanges, where the raised face on some non-standard and lapjoint flanges has a tapered bearing face that requires a compensating bevel washer to achieve uniform bolt load distribution.
When a bolt is tightened against an inclined surface without a beveled washer, the bolt shank is forced to bend at the nut bearing face to accommodate the slope. The bending moment M = F × e, where F is the bolt preload and e is the eccentricity created by the slope (e = t_washer × tanθ, where θ is the inclination angle). For a 1:14.5 taper (θ ≈ 4°) and a nut bearing face thickness of 20 mm, e ≈ 1.4 mm. The resulting bending stress at the critical thread root section adds directly to the tensile preload stress and reduces the fatigue life of the bolt by a factor of 2–5× depending on the bolt grade and application. AISC specification and BS EN 14399 both require beveled washers wherever the surface slope at the bolt bearing face exceeds 1:20 (approximately 2.9°).
Beveled Washer Anatomy
Types of Beveled Washers
Standard Bevel Angles, Dimensional Data
& AISC / BS EN 14399 Requirements
AISC · BS EN 14399 · Eurocode 3 · DIN 434 / DIN 435
Standard Bevel Angles — Selection Guide
The two dominant bevel angles for industrial beveled washers are determined by the geometry of the mating structural or piping component:
- 1:14.5 (approximately 4°) — The standard bevel angle for structural I-beam (UB/UBP) and H-section (UC/HD) flange tapers. The inner face of the rolling-formed flanges of I and H sections has a taper of approximately 1:14.5 (1 mm rise per 14.5 mm run) due to the rolling process. Per AISC Specification for Structural Steel Buildings (Section J3.2c) and BS EN 14399-6, beveled washers with a 1:14.5 taper are required under bolt heads and nuts bearing on the tapered inner faces of I and H section flanges.
- 1:6 (approximately 9.5°) — Used for steeper flange tapers including some channel sections (UPN, PFC) and in specific pipe flange applications where the raised face taper or lap joint collar taper requires compensation. Also used for some non-standard beam sections with steeper flange tapers.
- Custom bevel angles — For non-standard applications (inclined baseplates, tapered brackets, equipment pads), custom bevel angles are manufactured to drawing. Always specify the bevel ratio (e.g. 1:8) or angle (in degrees) precisely — a 1° error in bevel angle at M30 produces approximately 0.5 mm step at the washer edge, which is enough to create a significant stress concentration at the bolt thread root.
| Bolt Size | Hole Dia. (mm) | OD (mm) | Thick (Thin Edge, mm) | Thick (Thick Edge, mm) | Bevel Ratio |
|---|---|---|---|---|---|
| M12 | 13.5 | 37 | 3.0 | 5.6 | 1:14.5 |
| M16 | 17.5 | 44 | 3.0 | 6.0 | 1:14.5 |
| M20 | 22.0 | 52 | 4.0 | 7.5 | 1:14.5 |
| M22 | 24.0 | 56 | 4.0 | 8.0 | 1:14.5 |
| M24 | 26.0 | 62 | 4.0 | 8.5 | 1:14.5 |
| M27 | 30.0 | 66 | 5.0 | 9.5 | 1:14.5 |
| M30 | 33.0 | 72 | 5.0 | 10.0 | 1:14.5 |
| M36 | 39.0 | 85 | 6.0 | 12.0 | 1:14.5 |
| M42 | 45.0 | 100 | 7.0 | 14.0 | 1:14.5 |
| M48 | 52.0 | 115 | 8.0 | 16.0 | 1:14.5 |
DIN 434 (round beveled washers for I-sections, bevel 1:14.5). DIN 435 covers square beveled washers for the same application (U-sections and I-sections). Hole diameter = bolt diameter + 1.5 mm for sizes up to M24; + 2.0 mm for M27–M36; + 3.0 mm for M42–M72. All dimensions in mm. Thick edge is always towards the web of the beam; thin edge towards the flange tip. Tolerances on bevel angle: ±0.5° per DIN 434. Material: carbon steel yield ≥240 MPa per DIN 434; hot-dip galvanised or zinc-plated as standard. SS 304/316 available to order.
| Bolt Size | Hole Dia. (mm) | Side Length (mm) | Thick (Thin Edge, mm) | Thick (Thick Edge, mm) | Bevel Ratio |
|---|---|---|---|---|---|
| M12 | 13.5 | 37×37 | 3.0 | 5.6 | 1:14.5 |
| M16 | 17.5 | 44×44 | 3.0 | 6.0 | 1:14.5 |
| M20 | 22.0 | 52×52 | 4.0 | 7.5 | 1:14.5 |
| M24 | 26.0 | 60×60 | 4.0 | 8.5 | 1:14.5 |
| M27 | 30.0 | 66×66 | 5.0 | 9.5 | 1:14.5 |
| M30 | 33.0 | 72×72 | 5.0 | 10.0 | 1:14.5 |
| M36 | 39.0 | 85×85 | 6.0 | 12.0 | 1:14.5 |
| M42 | 45.0 | 100×100 | 7.0 | 14.0 | 1:14.5 |
DIN 435 (square beveled washers for I and U-sections, bevel 1:14.5). Square washers provide a positive orientation reference for the bevel direction relative to the beam web. Must be installed with thick edge towards the beam web. Tolerance on bevel angle ±0.5°. For connections on the outer (flat) face of I-beam flanges, standard flat washers per DIN 125 are used instead — beveled washers are only required on the inner tapered face.
Material Grades, Coatings
& Applicable Standards
DIN 434 · DIN 435 · ASTM F436 · BS EN 14399
| Material | Grade / Standard | Coating | Hardness | Typical Application |
|---|---|---|---|---|
| CS Standard | S235 / S355 per DIN 434 | HDG or Zinc Electroplate | ≥120 HV (soft) | General structural steelwork, indoor and outdoor |
| CS Hardened | ASTM F436 Type 1 | HDG or Xylan 1070 | HRC 38–45 | High-strength A325/A490 structural bolts (AISC) |
| SS 304 / A2 | ISO 7089/A2 / DIN 434 | Passivated | ≤30 HRC | Indoor/covered structural, light corrosive environments |
| SS 316 / A4 | ISO 7089/A4 / DIN 434 | Passivated or Xylan | ≤30 HRC | Marine, offshore, coastal structural, chemical |
| Duplex 2205 | A182 F51 / EN 1.4462 | Passivated or Xylan | ≤28 HRC (NACE) | Offshore structural, sour service, high-chloride |
| Brass / Bronze | CuZn37 / CuSn6 | Bare or lacquered | Soft | Electrical, non-magnetic, decorative applications |
| Standard | Scope | Bevel | Notes |
|---|---|---|---|
| DIN 434 | Round beveled washers for I-sections (metric) | 1:14.5 | Nominal sizes M12–M48; hole dia, OD, thin and thick thickness specified |
| DIN 435 | Square beveled washers for I and U-sections (metric) | 1:14.5 | Square plan; same bolt sizes as DIN 434; thick edge toward web |
| BS EN 14399-6 | HR/HV bolt assembly components including beveled washers | 1:14.5 | European structural bolt assembly standard; supersedes BS 4320 in UK |
| ASTM F436 | Hardened structural steel washers (inch series) | 1:14.5 Type 2 | Type 2 = beveled; for use with A325/A490 on beam flanges per AISC/RCSC |
| ASME B18.22.1 | Plain washers (inch series) | Custom | Beveled versions to customer specification referencing this standard |
| ISO 7089 / 7090 | Plain and hardened flat washers (metric) | N/A (flat) | Beveled versions are non-standard; manufactured to DIN 434/435 or customer drawing |
Square beveled washers per DIN 435 must be installed with the thick edge of the washer towards the web of the I-beam or H-section and the thin edge towards the outer tip of the flange. This orientation compensates for the inward taper of the beam flange, bringing the flat face of the washer to a position perpendicular to the bolt axis. Installed with the opposite orientation (thick edge towards flange tip), the beveled washer increases the effective angle of inclination at the bolt bearing face — producing greater bolt bending stress than if no washer were used at all. Always verify the orientation before tightening. An arrow or orientation mark on the washer OD pointing towards the web is recommended for complex multi-bolt connections.
Applications, Installation Notes
& Quality Control and Documentation
Pipe Flange · AISC · EN 14399 · EN 10204 MTC
Applications by Industry
Beveled washers per DIN 434 (round) and DIN 435 (square) are mandatory for all high-strength bolted connections to the inner (tapered) face of I-beam (UB/UBP) and H-section (UC/HD) flanges in structural steelwork per AISC Specification J3.2c and Eurocode 3 BS EN 1993-1-8. Common connection types requiring beveled washers include: beam-to-column moment connections, haunch connections in portal frames, wind bracing connections where the gusset plate bolts pass through the beam flange, and beam splice connections. Standard beam design tables (AISC SCM, SCI P358/P399) specify the washer requirement for each connection type.
Highway and railway bridge fabrication uses a very high density of bolted connections to I-section stringers, cross-girders, main girders and bracing members. All inner flange connections require beveled washers. Bridge connections are typically in high-strength friction grip (HSFG) bolt assemblies per BS EN 14399 or A490/A325 per AISC. The beveled washer is part of the bolt assembly specification — it is supplied pre-kitted with the bolt and nut as a complete assembly set. Bridge washers are always hot-dip galvanised (HDG) for outdoor exposure durability.
Offshore platform topsides structural connections using H-section and I-section members require SS 316 or duplex 2205 beveled washers to match the corrosion-resistant fastener specification. Offshore structural connections per NORSOK S-001 and API RP 2A use high-strength bolts in friction-type connections, and the beveled washers are part of the bolt assembly specification. All offshore beveled washers require EN 10204 3.1 MTC as minimum; EN 10204 3.2 with TPI for safety-critical connections.
Electrical transmission towers (lattice steel) and wind turbine monopole towers use angle section and I-section members extensively, with high-density bolted connection zones at section laps. The tapered inner faces of angle legs and I-section flanges in these connections require beveled washers throughout the connection zone. Hot-dip galvanised beveled washers (DIN 434/435) are standard for transmission towers (outdoor exposure for 50+ year design life). Wind turbine tower base flange connections use heavy-section bolted connections with large-bore beveled washers in S355 or higher-grade steel.
Some non-standard pipe flange configurations — particularly lap joint assemblies where the stub end collar angle does not match the backing flange bore face, or where tapered face flanges are used in certain pressure vessel configurations — require beveled washers between the nut/bolt head and the flange face to ensure uniform bolt preload distribution. The required bevel angle is determined by the flange face taper from the flange dimensional drawing. Custom bevel angles (1:6, 1:8, or specific degrees) are manufactured for piping applications that fall outside the standard 1:14.5 structural range.
Quality Control
QC for beveled washers covers: (1) Bevel angle verification — measured with a precision angle gauge or CMM against the drawing specification (DIN 434/435: ±0.5°); (2) Dimensional inspection — OD (round) or side length (square), hole diameter, thin edge thickness, thick edge thickness — all per DIN 434/435 or customer drawing; (3) Hardness — per ASTM F436 for hardened structural versions (HRC 38–45); (4) Coating adhesion and thickness — for HDG (ISO 1461), zinc plate (ISO 4042), Xylan (IFI-125); (5) PMI — 100% XRF on SS, duplex and exotic alloy washers; (6) Visual inspection — bevel uniformity, absence of casting defects, rolled edge quality, hole perpendicularity to flat face.
- Every beveled washer marked with the thick edge direction (arrow or raised rib) to prevent reversed installation on site
- Square beveled washers packed with consistent orientation in each tray or bag — reduces assembly errors significantly
- Bevel angle and direction confirmed in the dimensional inspection report for every lot
- HDG coating thickness per ISO 1461 minimum 45 µm on all surfaces including bevel face; confirmed by magnetic gauge measurement
| # | Document | Standard | Minimum Requirement |
|---|---|---|---|
| 01 | Material Test Certificate (MTC) | EN 10204 3.1 / 3.2 | 3.1 standard; 3.2 (TPI) for offshore structural, duplex, safety-critical |
| 02 | Dimensional Inspection Report | DIN 434 / DIN 435 / customer drawing | OD/side, hole dia, thin/thick edge thickness, bevel angle — all confirmed per lot |
| 03 | Bevel Angle Verification Certificate | DIN 434 / DIN 435 / ASTM F436 | Bevel ratio and angle measured; within ±0.5° tolerance; thick/thin edge identified |
| 04 | Hardness Test Report | ASTM E18 / ISO 6508 | Mandatory for ASTM F436 Type 2 hardened beveled washers; HRC 38–45 confirmed |
| 05 | PMI Report (XRF) | Project specification | 100% SS 316, duplex and exotic alloy beveled washers; grade confirmed |
| 06 | ISPM-15 Phytosanitary Certificate | IPPC / FAO | All wood packing for international export |
RR Hydraulics manufactures and exports beveled washers in round (DIN 434) and square (DIN 435) forms in bevel ratios 1:14.5 and 1:6, and custom bevel angles to drawing. Available in carbon steel (HDG per ISO 1461, zinc electroplate, Xylan 1070 coated), hardened per ASTM F436 Type 2, SS 304 and SS 316, Duplex 2205 and brass/bronze. Bolt sizes M12–M72 and 1/2"–2-1/2" inch series. EN 10204 3.1/3.2 MTC, dimensional inspection, bevel angle verification certificate, hardness (F436 hardened), PMI (SS/duplex). 48-hour express dispatch on standard DIN 434/435 stock sizes in CS HDG.