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Square Taper Washer Dimensions (DIN 434 and DIN 435, M8 to M27)
Guide · Updated October 28, 2026
DIN 434 and DIN 435 cover square taper washers for bolting through sloped steel flanges, M8 to M27. DIN 434 has an 8% slope for U-channels; DIN 435 has a 14% slope for I-beams. Hole, side lengths and DIN 434 thickness agree across the fasteners.eu DIN 434 table, the neue-physik.de DIN 434 / 435 table and the Impacivata DIN 434-435 sheet; DIN 435 thickness agrees across neue-physik.de, Impacivata and the Ferretería Bonet DIN 435 sheet. Skipped: the hole at M12 and M16 (13.5 / 17.5 vs 14 / 18 mm), thin-edge e, M30, tolerances and weights. Check your supplier for critical work.
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Step by step
- Identify the section: U-channel (parallel flange channel with 8% taper) takes DIN 434. I-beam (taper flange, 14%) takes DIN 435.
- Pick the bolt size: Choose M8 to M27 to match the bolt through the flange.
- Read the size: Side lengths a and b give the square footprint; check it fits the flange width.
- Read the thickness: h is the thick-edge thickness; DIN 435 is thicker because its slope is steeper.
- Orient it: Put the thick edge toward the flange tip so the bolt head or nut seats square to the bolt.
- Order it: Designate as Washer DIN 434 - 13.5 (standard, hole size) or by bolt size with your supplier.
DIN 434 / DIN 435 taper washer dimensions (mm)
Columns: bolt size, hole d, side lengths a and b, thick-edge thickness h for DIN 434 (8%) and for DIN 435 (14%). A dash means sources conflict.
- Bolt | Hole d | a | b | h DIN 434 (8%) | h DIN 435 (14%)
- M8 | 9 | 22 | 22 | 3.8 | 4.6
- M10 | 11 | 22 | 22 | 3.8 | 4.6
- M12 | — | 26 | 30 | 4.9 | 6.2
- M16 | — | 32 | 36 | 5.9 | 7.5
- M20 | 22 | 40 | 44 | 7 | 9.2
- M22 | 24 | 44 | 50 | 8 | 10
- M24 | 26 | 56 | 56 | 8.5 | 10.8
- M27 | 30 | 56 | 56 | 8.5 | 10.8
Worked example: M20 through an I-beam flange
For an M20 bolt through a taper-flange I-beam, use DIN 435 - 22: 22 mm hole, 40 x 44 mm square, 9.2 mm at the thick edge. Through a U-channel flange the DIN 434 washer is the same size but 7 mm thick. Add the washer thickness to the grip length.
Common problems
- Wrong slope: an 8% washer on an I-beam still leaves the nut tilted; check the section.
- Washer turned the wrong way: the thick edge must face the flange tip.
- Washer too wide: check side length a against the flange width at the hole.
FAQ
Which is which: DIN 434 or DIN 435?
DIN 434 has an 8% slope for U-sections (channels). DIN 435 has a 14% slope for I-sections (taper-flange I-beams). Both share the same holes and side lengths.
Why use a taper washer?
Channel and I-beam flanges are sloped on the inside. Without a taper washer the bolt head or nut sits on an angle and the bolt bends when tightened.
Why is the hole blank at M12 and M16?
Sources split between 13.5 / 17.5 mm and 14 / 18 mm holes for those sizes, so we left the cells out rather than guess.
What was skipped?
The thin-edge thickness e (sources differ at M24 and M27), M30 (only one source), tolerances and weights.
Do they work on parallel flange beams?
No. Modern parallel flange (IPE, HE, UPE) sections need flat washers such as DIN 7989.
Related guides and calculators
- HV structural bolts (DIN 6914)
- HV structural washers (DIN 6916 / ISO 7416)
- Square washers for timber (DIN 436)
- Heavy-duty washer dimensions (DIN 7989)
- Flat washer size chart (SAE, USS, metric)
- Clamping washer dimensions (DIN 6340)
- Hex nut with collar dimensions (DIN 6331)
- All free machinist calculators
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General shop information only — follow your drawing, tool maker's data and your quality system.