Skip to content
info@engineeringhardware.com
Request a Quote

Nuts · GB/T 39 / ISO 4034

M20 Square Nut, Metric Dimensions & Specifications

M20 Square Nut, Metric Dimensions & Specifications reference image

This page covers M20 Square Nut, Metric to GB/T 39 / ISO 4034: the full dimensional row, hole and tool sizes, proof-load data and typical applications. All values are taken from the governing standards (GB/T 39 / ISO 4034 together with ISO 273, ISO 724 and ISO 898-1 where applicable).

M20 Dimensional Row (GB/T 39 / ISO 4034)

SizePitch (mm)Width across flats s (mm)Nut height m (mm)Reference standard
M202.530.012.0GB/T 39 / DIN 562

Spanner & Drive for M20 Square Nut, Metric — GB/T 39 / ISO 4034 (Series 076)

Drive geometry for M20 Square Nut, Metric — GB/T 39 / ISO 4034 (Series 076) is given by the row above; match the tool to the listed values.

Common Applications for M20 Square Nut, Metric — GB/T 39 / ISO 4034 (Series 076)

M20 Square Nut, Metric — GB/T 39 / ISO 4034 (Series 076) are commonly specified for structural joints, flange connections and heavy equipment foundations.

Installation Tips for M20 Square Nut, Metric — GB/T 39 / ISO 4034 (Series 076)

  • 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

Pair M20 with the matching M20 bolt or screw, plus a M20 flat washer where required to distribute load on softer materials.

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 39 / ISO 4034)

SizePitch (mm)Width across flats s (mm)Nut height m (mm)Reference standard
M30.55.51.8GB/T 39 / DIN 562
M40.77.02.2GB/T 39 / DIN 562
M50.88.02.7GB/T 39 / DIN 562
M61.010.03.6GB/T 39 / DIN 562
M81.2513.04.8GB/T 39 / DIN 562
M101.517.06.0GB/T 39 / DIN 562
M121.7519.07.0GB/T 39 / DIN 562
M162.024.09.0GB/T 39 / DIN 562
M202.530.012.0GB/T 39 / DIN 562
M243.036.014.0GB/T 39 / DIN 562

Frequently Asked Questions

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 Square Nut, Metric — GB/T 39 / ISO 4034 (Series 076) 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.

What is the height of an M20 nut?

The nominal height of a style-1 ISO 4032 M20 nut is in the spec table on this page. Style-2 (thick) is approximately 1.1× this height; thin (ISO 4035 / DIN 439) is approximately 0.5×.

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.