Skip to content
info@engineeringhardware.com
Request a Quote

Washers · GB/T 858

M20 Plain Washer Dimensions & Specifications

M20 Plain Washer Dimensions & Specifications reference image

This page covers M20 Plain Washer to GB/T 858: the full dimensional row, hole and tool sizes, proof-load data and typical applications. All values are taken from the governing standards (GB/T 858 together with ISO 273, ISO 724 and ISO 898-1 where applicable).

M20 Dimensional Row (GB/T 858)

For bolt sizeInner diameter d1 (mm)Outer diameter d2 (mm)Thickness t (mm)Reference standard
M2021.037.03.0ISO 7089 / GB/T 97.1

Spanner & Drive for M20 Plain Washer — GB/T 858 (Series 071)

Drive geometry for M20 Plain Washer — GB/T 858 (Series 071) is given by the row above; match the tool to the listed values.

Common Applications for M20 Plain Washer — GB/T 858 (Series 071)

M20 Plain Washer — GB/T 858 (Series 071) are commonly specified for high-load load-spreading on structural joints.

Installation Tips for M20 Plain Washer — GB/T 858 (Series 071)

  • At M20 the stretch in the bolt becomes the controlling factor — for critical joints, use angle-controlled or stretch-controlled tightening instead of pure torque.

Mating Parts for M20

A M20 flat washer pairs with a M20 bolt/screw and matching M20 nut.

Technical Drawing

Customize the parameters below — every spec field is editable, and the drawing redraws to match the values you choose. Changing the size will snap the other fields to that size's standard values; you can then override any individual value.

Sends the selected values to the quote form below.

Request a Quote

Adjust the parameters in the drawing above and click "Request this configuration" to send the exact specification straight to this form.

Request a Quotation

Specification
Business Information

Dimensions & Specifications (GB/T 858)

For bolt sizeInner diameter d1 (mm)Outer diameter d2 (mm)Thickness t (mm)Reference standard
M33.27.00.5ISO 7089 / GB/T 97.1
M44.39.00.8ISO 7089 / GB/T 97.1
M55.310.01.0ISO 7089 / GB/T 97.1
M66.412.01.6ISO 7089 / GB/T 97.1
M88.416.01.6ISO 7089 / GB/T 97.1
M1010.520.02.0ISO 7089 / GB/T 97.1
M1213.024.02.5ISO 7089 / GB/T 97.1
M1415.028.02.5ISO 7089 / GB/T 97.1
M1617.030.03.0ISO 7089 / GB/T 97.1
M1819.034.03.0ISO 7089 / GB/T 97.1
M2021.037.03.0ISO 7089 / GB/T 97.1
M2425.044.04.0ISO 7089 / GB/T 97.1
M3031.056.04.0ISO 7089 / GB/T 97.1
M3637.066.05.0ISO 7089 / GB/T 97.1

Frequently Asked Questions

What is the coarse-thread pitch of M20 for Plain Washer — GB/T 858 (Series 071)?

For M20 the standard coarse pitch is 2.5 mm — this is the value used for Plain Washer — GB/T 858 (Series 071).

What clearance and tapping drill suit M20?

Use a 22 mm clearance hole (ISO 273 medium) for through-fixing, or a 17.5 mm tapping drill for a coarse M20 thread.

Should M20 Plain Washer — GB/T 858 (Series 071) be tightened by torque or by angle?

For critical structural joints at M20, angle-controlled or stretch-controlled tightening is more repeatable than pure torque — the friction scatter at large diameters can dominate the torque signal.

What grip range is typical for M20 structural bolts?

Grip ranges are highly application-dependent at M20. As a guide, choose a length that gives at least 1× the thread diameter engagement in the nut plus 2–3 thread pitches projecting.

How do I request a quotation?

Use the technical drawing on this page to pick the exact configuration, then submit it with the quote form. We respond within one business day.