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IS 5374:1990 is the Indian Standard (BIS) for taper washers for i-beams. This standard specifies the material, dimensions, finish, and designation requirements for steel taper washers. These washers are specifically designed to provide a flat bearing surface for bolt heads and nuts when fastening components to the sloped flanges of I-beams and channel sections.
Specifies dimensions and other requirements for taper washers for use with I-beams.
Overview
Status
Current
Usage level
Specialized
Domain
Structural Engineering — Fasteners, Bolts and Anchors
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! Essential for achieving correct bolt pretension and preventing localized bending in the bolt when connecting to tapered flanges of structural sections like ISMB, ISMC etc.
! There are two distinct types specified: square washers for I-beams (with a 1:6 taper) and wedged washers for channels. Ensure the correct type is used for the corresponding structural section.
! Though the code references the withdrawn IS 226, use steel conforming to IS 2062 for material.
Consolidated list per BIS. For the text of each amendment, refer to the BIS portal link above.
steelfasteners
International Equivalents
Similar International Standards
ASME B18.21.1-2009 (R2019)American Society of Mechanical Engineers (ASME), USA
HighCurrent
Washers: Helical Spring-Lock, Tooth Lock, and Plain Washers (Inch Series)
Specifies 'Beveled Washers' (square and round) with an identical 1:6 taper for use on tapered structural flanges.
DIN 434Deutsches Institut für Normung (DIN), Germany
MediumWithdrawn
Square taper washers for U-sections
Covers square taper washers for channel sections, but with a different taper (8% vs 1:6).
JIS B 1257:1999Japanese Industrial Standards (JIS), Japan
MediumCurrent
Taper washers
Specifies square taper washers with 5° and 8° tapers; the 8° taper is functionally similar to the 1:6 (9.46°) of IS 5374.
Key Differences
≠The specified taper angle is the most significant difference. IS 5374 mandates a 1:6 taper (~9.46°) to match Indian I-beams. ASME B18.21.1 also uses 1:6, but DIN 434 specifies an 8% taper (~4.57°) for U-channels, and JIS B 1257 offers 5° and 8° options.
≠Material specifications vary. IS 5374 requires steel conforming to IS 2062 (structural steel), while ASME B18.21.1 allows for carbon steel or malleable iron, and DIN standards typically use general-purpose structural steel like S235JR.
≠While IS 5374 and ASME B18.21.1 both specify square (Type A) and round (Type B) washers, the most common German equivalent (DIN 434) is primarily for square washers only.
≠Dimensional series differ, especially between metric (IS, DIN, JIS) and inch-based (ASME) standards. This leads to slight variations in outer dimensions and thicknesses for nominally equivalent bolt sizes.
Key Similarities
≈The fundamental purpose is identical: to provide a flat, parallel bearing surface for a bolt head or nut on the inclined flange of a structural I-beam or channel section.
≈All standards specify a square washer as a primary option (e.g., IS 5374 Type A, DIN 434, ASME 'Square Beveled'). The square shape helps prevent rotation during tightening.
≈The basic dimensional relationship is consistent across standards, where the inner diameter, outer dimensions, and thickness are all specified based on the nominal bolt size the washer is intended to be used with.
≈These washers are generally intended for standard structural bolting applications, and are distinct from the hardened, high-performance washers specified for high-strength friction grip (HSFG) or pre-tensioned bolting assemblies.
Parameter Comparison
Parameter
IS Value
International
Source
Washer for Bolt Size
M20
M20
DIN 434
Taper / Bevel
1:6 (approx. 9.46°)
8% (approx. 4.57°)
DIN 434
Taper / Bevel
1:6
1:6
ASME B18.21.1
Inner Diameter (for M20)
22.0 mm
22.0 mm
DIN 434
Outer Dimension (Side 'a' for M20 Square)
40 mm
40 mm
DIN 434
Outer Dimension (Side 'a' for 3/4" Square)
40 mm (for M20)
1.75" (44.45 mm) (for 3/4" bolt)
ASME B18.21.1
Material Grade
Steel as per IS 2062
Carbon steel or malleable iron
ASME B18.21.1
⚠ Verify details from original standards before use
Key Values4
Quick Reference Values
Taper for square washers1:6
Hardness range (HV)140 to 250
Material specificationMild steel as per IS 2062
Taper for channel washers98 degrees (angle)
Tables & Referenced Sections
Key Tables
Table 1: Dimensions for Taper Washers (Square) for I-Beams
Table 2: Dimensions for Taper Washers for Channels
To provide a parallel surface for the nut and bolt head on a non-parallel (tapered) surface, like the flange of an I-beam, ensuring uniform load distribution and preventing bolt bending.
What is the standard taper for washers used on I-beams?+
The standard taper is 1 in 6 (Clause 2.1 and Fig. 1).
How is a taper washer for a 20 mm bolt designated?+
As 'Taper Washer 20 IS 5374' for a square type, or 'Channel Washer 20 IS 5374' for a channel type (Clause 5).
What material is specified for taper washers?+
Mild steel conforming to IS 226 (now superseded by IS 2062) (Clause 3.1).