STAINLESS STEEL AFNOR FLAT WASHERS NFE 25-514 TYPE M

AFNOR Flat Washers NFE 25-514 Type M — Type M is the next step up from Type Z within the same NFE 25-514 range, trading a slightly larger outside diameter and thickness for greater load-spreading capacity at the same nominal bolt diameter - the AFNOR system's equivalent of moving from a small-series to a normal-series washer. In practice, Type M tends to function as the general-purpose default within the range, much as the normal series is the default choice in DIN and ISO systems: it is the size reached for when nothing about the joint specifically calls for the tighter clearance of Type Z or the extra bearing area of Type L or LL. Like any flat washer, its core job is straightforward - spread the fastener's clamping force over a wider area than the head alone provides, and give a flat, even bearing surface against a clamped material that may not itself be perfectly true. Where the surrounding assembly is being sourced under French or AFNOR specification, Type M is usually the right starting point unless the drawing specifically calls for one of the other three sizes, and it is always worth confirming that explicitly rather than assuming M is correct by default, since the four sizes are not interchangeable without checking the drawing. Material selection follows the same general pattern as other flat washers: mild steel with a protective finish for indoor and general engineering work, A2 (304-equivalent) stainless as the sensible default the moment the assembly is outdoors or subject to washdown, and A4 (316-equivalent) worth the extra cost specifically for coastal, marine, or chemically exposed installations, where A2's corrosion resistance eventually runs out under sustained chloride attack. To specify correctly, match the bore to the bolt diameter and confirm the drawing genuinely calls for the medium (M) series rather than the smaller Z or the larger L and LL alternatives.

FAQs
How does Type M compare to Type Z?
Type M has a larger outside diameter and/or thickness than Type Z, giving greater load-spreading capacity, while Type Z offers a more compact footprint where clearance is restricted.

How does Type M compare to Type L and LL?
Types L and LL provide progressively larger outside diameters than Type M, offering greater load spreading for softer materials or larger clearance holes, at the cost of a larger footprint.

Is Type M the default choice within the NFE 25-514 range?
Type M is commonly used as a general-purpose selection within the range, similar to the normal series in DIN/ISO systems, but the correct type should always be confirmed against the drawing.