STAINLESS STEEL BUMAX FLAT WASHERS

Bumax Large Series Flat Washers ISO 7093-1 200HV — Made to ISO 7093-1, which specifies a wider outside diameter than a standard-series flat washer along with a controlled 200 HV hardness class, this washer is designed specifically for structural and high-tensile bolted connections rather than general assembly work. The 200 HV rating refers to the washer's hardness on the Vickers scale — a higher, tightly controlled hardness resists indentation and creep under the sustained clamping load of a high-tensile joint, which matters because a washer that deforms under load lets preload relax over time, loosening the joint without any sign of the fastener itself failing. The larger outside diameter defined by ISO 7093-1 spreads that same load over a wider bearing area, which is why this washer size is specified in structural steelwork, bridge and rail connections, and other applications using oversized or slotted clearance holes, where a standard-series washer wouldn't adequately bridge the gap or distribute load across the joint face. Manufactured in Bumax's A4/316 stainless, it pairs the ISO 7093-1 dimensional and hardness spec with corrosion resistance well beyond standard A2 stainless or plated carbon steel, making it suited to structural connections in marine, coastal, or chemically exposed environments — where a structural joint is dry and sheltered, a standard zinc-plated or A2 large-series washer to the same ISO spec is usually the more economical choice, and the Bumax premium is best reserved for projects where corrosion resistance and mill-traceable documentation both matter. Choosing between this and Bumax's standard flat washer comes down to hole size and load-spreading requirement: specify the large series wherever the design calls for oversized or slotted holes, or wherever the applicable structural design code specifies a large-series washer under a high-tensile bolt or nut. As with the rest of the range, every batch is traceable to the original mill for certification purposes.

FAQs
When does a structural design code require a large-series washer rather than a standard one?
Many structural steelwork codes call for large-series washers under high-tensile bolts, particularly where slotted or oversized clearance holes are used; the applicable design standard for the specific project should be checked to confirm the requirement.

How does this compare with a standard Bumax flat washer in practice?
The material and hardness class are the same across both; the large series version simply has a bigger outside diameter, so it's specified wherever load needs spreading over a wider area or the clearance hole is larger than standard.

Is this washer suitable for general, non-structural assembly work?
It can be used generally, but its larger size and hardness rating are primarily there to serve structural and high-tensile applications — a standard-series Bumax flat washer is usually the more economical fit for ordinary assembly work.