Product and application brief
A flat square washer is a plate with a square outside profile and a clearance hole for the mating fastener. It provides a defined bearing interface beneath a nut or bolt head. The outside size, hole diameter and plate thickness are separate selection fields; the word square does not establish a structural rating or make a washer interchangeable with a tapered or hardened form.
Product forms and reference names
| Product form / field | Reference and distinguishing details |
|---|---|
| Flat square washer | A flat plate with parallel bearing faces and a square outer profile. Identify the side dimension, clearance-hole size and thickness independently. |
| DIN 436 reference | DIN 436:2024-10 identifies square washers, especially for wood constructions. Select the exact specification and edition; not every square plate sold under a trade description is established as compliant. |
| Drawing-based square plate | Other side dimensions, hole positions, slot shapes or corner details need a controlled drawing. Do not assume a modified hole or enlarged plate remains the same standard part. |
| Square taper / beveled washer — different form | A square outer profile can also appear on tapered washers. Those have non-parallel bearing faces and belong to the separate beveled-washer selection; confirm the required slope and mating surface rather than substituting by appearance. |
Outside size, hole and thickness
Specify the side dimension or both outside dimensions where the plate is rectangular rather than square. Give the hole diameter and position, plate thickness and required corner or edge detail. A nominal bolt-size label is a selection reference, not the measured hole diameter. Use the drawing or applicable standard for the actual values and tolerances.
Standard edition and material selection
The DIN Media catalogue identifies DIN 436:2024-10 as the current edition and shows replacement of DIN 436:1990-05. Supplier catalogues may use approximate-reference notation such as ~DIN 436; that notation should not be silently converted into a conformity statement. Material, hardness and finish must be specified separately for the chosen part.
Bearing interface and drawing-based variants
Match the hole clearance and bearing geometry to the mating bolt, nut and support surface. For timber or another assembly, provide the relevant joint or mating drawing where it controls the plate size or finish. This page does not calculate joint capacity, prescribe tightening torque or establish an approved structural substitution.
Specification fields
| Product form / field | Reference and distinguishing details |
|---|---|
| Product identity | Flat square form, exact standard and edition or controlled drawing/revision; distinguish tapered and special-hole plates. |
| Outside geometry | Side dimension, corner/edge requirements and required tolerances; identify rectangular plates explicitly. |
| Hole | Diameter or slot dimensions, hole location, number of holes where non-standard and mating fastener reference. |
| Thickness and faces | Plate thickness and any specified flatness, bearing-face or edge conditions; no universal thickness-to-bolt ratio assumed. |
| Material and finish | Material designation, required hardness where applicable, surface/coating specification and inspection documents. |
| Quantity and attachments | Quantity with units, size-by-size list and controlled drawings; list unresolved specifications separately. |
Common product questions
Is the bolt size the same as the washer hole diameter?
No. A nominal bolt-size label does not specify the exact clearance-hole diameter. Record the hole diameter, outside size and thickness from the selected standard or drawing.
Can a flat square washer replace a square tapered washer?
Not solely because the outside profile is square. Flat washers have parallel bearing faces; tapered washers need a specified slope and matching support geometry. Confirm the assembly requirements.
Does a DIN 436 reference prove compliance or structural capacity?
No. The reference identifies a product specification to check. Compliance requires the applicable part requirements and evidence; structural capacity and installation requirements come from the joint design, not the name or illustration.
Related washer types
Product references
References checked 6 October 2026 explain product identity. Third-party model names and approvals are not FastenerBridge brand affiliation, stock or certification claims. Final geometry and requirements follow the selected specification.