M20 Castle Nuts (DIN 935) dimensions to DIN 935: width across flats (spanner size) 30 mm, nut height 20 mm, coarse thread pitch 2.5 mm. Tighten to approximately 420 Nm at property class 8.8 in a dry, as-supplied condition.
- Width across flats (spanner size)
- 30 mm
- Nut height
- 20 mm
- Coarse thread pitch
- 2.5 mm
- Tightening torque (class 8.8)
- 420 Nm
Figures are nominal values from the governing standard. Confirm against the tolerance class for your application before machining or ordering.
Dimensional data for M20 Castle Nuts (DIN 935) to DIN 935, with the drive and the installation notes for this type.
Values are taken from the governing standard rather than from a general machine-thread table, because this type is not selected on one.
M20 Dimensional Row (DIN 935)
| Thread size | Pitch (mm) | Width across flats s (mm) | Total height m (mm) | Slot width n (mm) | Slot depth (mm) | Split pin size | Reference standard |
|---|
| M20 | 2.5 | 30.0 | 20.0 | 4.5 | 6.0 | 4 x 50 | DIN 935 |
Spanner & Drive for M20 Castle Nuts (DIN 935)
Drive geometry for M20 Castle Nuts (DIN 935) is given by the row above; match the tool to the listed values.
Tightening Torque for M20
| Class 8.8 (dry, ~µ 0.125) | ≈ 420 Nm |
|---|
| Class 10.9 (dry, ~µ 0.125) | ≈ 598 Nm |
|---|
| Class 12.9 (dry, ~µ 0.125) | ≈ 700 Nm |
|---|
Indicative dry-joint values. Lubrication can lower the required torque by 15–25%. Always confirm against the joint design, especially when going up a strength class.
Proof Load & Strength for M20
Nuts are graded to ISO 898-2 by the proof load the nut itself will hold (classes 04, 05, 5, 6, 8, 10 and 12), not by the 8.8 / 10.9 / 12.9 scale used for bolts. A class-8 nut is the correct mate for a class-8.8 bolt, and the joint is designed on the bolt, so no bolt-tension figure is quoted here.
Installation Tips for M20 Castle Nuts (DIN 935)
- 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.
Custom manufacturing · Made to drawing
Need castle nuts (din 935) in a size this table does not list?
This page covers M20 castle nuts (din 935). Thread size is the obvious variable and rarely the interesting one — height for clearance, across-flats for the tool already in the cell, and the locking feature for the vibration actually present. Made by cold heading or tapping.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
Custom nut manufacturingSend a drawing
Applications & Industries for M20 Castle Nuts
What Castle Nuts are specified for, industry by industry. Stocked from M8 to M24.
Industries that specify Castle Nuts
-
Agricultural & plant
Articulating joints not meant to be torqued solid.
-
Rail & heavy equipment
Inspectable, positively locked joints.
-
Automotive chassis
Wheel bearings, steering and suspension joints locked by a split pin.
-
Maintenance & MRO
Replacements matched to the existing bolt class, thread and finish.
-
Building services
Threaded rod, channel and suspension assemblies.
-
Machine building & OEM
The clamping counter-face on studs and bolts throughout an assembly.
Typical applications
- joints deliberately left free to articulate
- tighten to torque, then back off to the nearest slot
- positive locking with a split pin through a cross-drilled bolt
- locking an adjustment so it cannot drift
- joints re-torqued at a service interval
- completing a bolted joint on a stud, rod or bolt
Service conditions to specify against
- Marine and coastal
- Available in A4 (316) stainless for chloride exposure — coastal structures, pool halls, water treatment and deck hardware, where A2 will eventually pit.
- High load
- Supplied in ISO 898-1 property classes, so the joint can be designed to a stated proof load and tightened to a calculated torque rather than by feel.
- Match the class
- A nut below the bolt property class strips before the bolt reaches its own limit — pair class 8 nuts with 8.8 bolts, class 10 with 10.9.
Full application guide: where Castle Nuts are used, how to specify them, and the cases they are wrong for
