The M18 size of Phillips Countersunk Machine Screw is dimensioned by GB/T 819.1 / ISO 7046. The tables below give the dimensional row from the standard, the drill and spanner sizes that go with it, and the assembly torque per property class. The technical drawing on this page redraws to the exact values selected.
M18 Dimensional Row (GB/T 819.1 / ISO 7046)
| Size | Pitch (mm) | Length L (mm) | Head diameter dk (mm) | Head height k (mm) | Cross recess | Countersink angle (deg) | Reference standard |
|---|---|---|---|---|---|---|---|
| M18 | 2.5 | 100 | 33.0 | 9.0 | PH4 | 90 | ISO 7046 / GB/T 819 |
Spanner & Drive for M18 Phillips Countersunk Machine Screw — GB/T 819.1 / ISO 7046 (Series 029)
The hex socket for M18 Phillips Countersunk Machine Screw — GB/T 819.1 / ISO 7046 (Series 029) is shown in the spec table — use the matching Allen / hex key (an ISO 2936 hex key set covers the full range). For a one-off, a T-handle key and a calibrated arm will do. For a batch, the only way to get the same preload twice is a torque-controlled driver.
Hole Sizes for M18
| Coarse-thread pitch (ISO 724) | 2.5 mm |
|---|---|
| Through-hole / clearance (ISO 273 medium) | 20 mm |
| Tapping drill, coarse thread | 15.5 mm |
Tightening Torque for M18
| Class 8.8 (dry, ~µ 0.125) | ≈ 297 Nm |
|---|---|
| Class 10.9 (dry, ~µ 0.125) | ≈ 423 Nm |
| Class 12.9 (dry, ~µ 0.125) | ≈ 495 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 M18
| Tensile stress area As (ISO 724) | 192 mm² |
|---|---|
| Proof load, class 8.8 | 115 kN |
| Proof load, class 10.9 | 160 kN |
| Proof load, class 12.9 | 187 kN |
| Min. ultimate tensile load, class 8.8 | 160 kN |
Proof load = tensile stress area × the proof stress Sp of the class, per ISO 898-1 — Sp is a lower figure than the yield stress Rp0.2 and the two are not interchangeable. The stress area is computed from this size's own diameter and pitch, so a fine-pitch designation gives the fine-pitch figure. Design the joint so the working preload stays below the proof load of the class selected.
M18 Phillips Countersunk Machine Screw — GB/T 819.1 / ISO 7046 (Series 029) Weight
A steel M18 phillips countersunk machine screw at the listed 100 mm length weighs approximately 671 g each — about 671 kg per 1,000 pieces. Stainless A2/A4 weighs roughly the same (density 7.9–8.0 g/cm³).
Actual weight varies slightly with head form, thread and finish; use this figure for freight estimation only.
Installation Tips for M18 Phillips Countersunk Machine Screw — GB/T 819.1 / ISO 7046 (Series 029)
- Use a quality Allen key fully seated in the socket — partial engagement is the most common cause of stripped sockets at this size.
- For countersunk and button-head variants, chamfer the through-hole to seat the head flush without preloading the head/shank fillet.
- At M18 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 M18
For M18, pair with a M18 hex nut (ISO 4032 / DIN 934) and, where used, a M18 flat washer (ISO 7089 / DIN 125A) under the head and under the nut.
Custom manufacturing · Made to drawing
Need phillips countersunk machine screw in a size this table does not list?
This page covers M18 phillips countersunk machine screw. Lengths and thread lengths outside the standard table are the commonest request, followed by a drive the standard does not offer and a head marked with your own part number. Made by cold heading or warm forging.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
