Stainless Steel Square-Hole & Square Washers
Square-hole washers for carriage bolts, strut and channel framing, and square washers to DIN 436. Produced in 304, 316 and 316L stainless, with custom hole sizes made to your drawing.
Washers for anti-rotation and square seating.
A square hole locks the square neck of a carriage bolt so the fastener cannot spin while the nut is run down. A square outer shape gives a larger bearing face on timber and on slotted or oversized holes. Both are flat stamped parts.
We stamp them in 304, 316 and 316L stainless, to DIN 436 or to your own square size, slot or outer dimensions. We verify the grade with our own handheld XRF spectrometer (PMI) and can include the reading with your order.
Square-hole and square washers — when to use each.
They solve different problems. One holds the fastener against rotation; the other gives a square bearing face.
Square-hole washers — anti-rotation & load spread
A square (or slotted) aperture engages the square neck under a carriage bolt head, or seats over strut and channel hardware, so the fastener cannot spin while the nut is run down. The broad bearing face also spreads clamp load across slotted, oversized or soft material.
- Carriage / coach bolts where the square neck must be held
- Strut, channel and unistrut framing systems
- Slotted sheet, timber and soft-material connections
Square washers to DIN 436
DIN 436 covers square washers with a round hole, used mainly in timber construction and coach-bolt joints, where the square face spreads the load under the nut or bolt head. We produce them to DIN 436 — sizes on request.
- Timber construction and coach-bolt joints
- Square bearing face on soft, slotted or oversized holes
- DIN 436 sizes on request — send your size list
We do not make taper washers (DIN 434 / DIN 435), spring lock washers or tooth lock washers.
Made to your hole size.
With square-hole washers the geometry is usually set by your bolt, your channel or your fixture, so much of what we ship here is tooled to a drawing.
Send us the square aperture across the flats (or slot dimensions), the outer dimensions and the thickness. We tool it, run first-article inspection, and confirm before the main batch. The minimum for a non-standard item is 100 kg.
Square/slot size · outer dimensions · thickness · grade (304 / 316 / 316L) · quantity. A sketch, photo or sample is enough to start.
Grade matched to the environment.
The same square-hole washer behaves very differently outdoors and in a clean indoor frame. The grade sets the corrosion resistance.
304 — general structural duty
The default for indoor and sheltered steel framing, strut systems, machine bases and timber connections. Strong, cost-effective corrosion resistance for most builds.
316 / 316L — seawater, marine & coastal
The usual choice for seawater, marine and coastal use, with higher corrosion resistance than 304. Specify it for exterior structural fixings near the sea.
Finish & documents
One finish: plain stainless, tumble-polished in sawdust (wood chips); no plating or passivation. We verify the grade with our own handheld XRF spectrometer (PMI) and can include the reading with your order. We cannot issue EN 10204 3.1 mill certificates.
Square-hole & square washer questions.
Where are square-hole and square washers used?
Square-hole washers stop carriage bolts and similar fasteners from spinning in channel, strut, slotted sheet and timber. DIN 436 square washers are used mainly in timber construction, where the square face spreads the load under the nut or bolt head. Typical uses include strut and channel framing, timber joinery, fencing and decking.
Can you make custom square hole sizes?
Yes. Square holes, slots and special outer dimensions are stamped to your drawing or sample. Tell us the square aperture across the flats, outer dimensions, thickness and material, and we will tool and quote — first-article inspection is available before the main run.
Do you make DIN 436 square washers?
Yes. We produce square washers to DIN 436 in 304, 316 and 316L. Sizes are on request: send the sizes and quantities you need and we quote them. We do not make taper washers to DIN 434 or DIN 435.
Are these available in 304, 316 and 316L?
Yes — all three grades. 304 (A2) for general indoor and sheltered structural duty; 316 (A4) and 316L for seawater, marine and coastal use, with higher corrosion resistance than 304. Material is stamped to full thickness, with no under-gauge or recycled substitution. 304 vs 316 guide.
Can you make them to a drawing or sample?
Yes. Send the square aperture across the flats (or slot dimensions), outer dimensions, thickness and grade — a sketch or sample is enough to start. We tool the die in-house, run first-article inspection for your approval, then go to the main batch. The minimum for a non-standard item is 100 kg, and export orders start at about 600 kg in total.
How do you verify the material grade?
We verify the grade with our own handheld XRF spectrometer (PMI) and can include the reading with your order. We cannot issue EN 10204 3.1 mill certificates. Our quality system is ISO 9001:2015 certified (cert. 74326Q00174R001).
What hole shapes and sizes can you stamp?
Square holes are the most common request, sized to the bolt neck across the flats — M6 through large structural sizes. We also stamp slots, rectangular apertures and non-round holes to drawing. OD, ID and thickness are set per your spec. Coil-fed automated presses hold consistent tolerance across a run; for non-standard geometry we tool a custom die and confirm the first article before production.
Tell us what you need.
Send specs or a drawing and we will come back with pricing, lead time and material options. No account needed.
- ✓ 304 / 316 / 316L, DIN & ASME or custom
- ✓ Replies from our sales team, usually within one business day
- ✓ Samples on request, courier freight paid by the buyer