Reference illustration — produced to your drawing
Bolts
Square Head Bolts
A bolt with a four-sided square head and a plain or partially threaded shank. The square head gives a large wrench bearing surface.
Used in timber structures, machinery, and older equipment restoration. Bought by fabricators and machinery maintenance suppliers.
Standard
ASME B18.2.1
Size range
M6 – M30 · 1/4 – 1-1/4 in
MOQ
From 50 pcs
Lead time
Samples 5–10 days
What we produce
- Carbon steel or stainless steel 304
- Square head with plain or partial thread shank
- Metric and inch threads
- Hot-dip galvanized or zinc finish
Specification notes
- Common lengths from 20 mm to 200 mm
- Pairs with a square or hex nut
- Heavy square head variant available
Specifications
Every line below is a starting point, not a limit. Non-standard sizes, special threads and unusual materials are what we do — send the drawing and we confirm what fits.
| Standard | ASME B18.2.1 |
|---|---|
| Size range | M6 – M30 · 1/4 – 1-1/4 in |
| Threads | Metric coarse · UNC · UNF |
| Head / geometry | Square head driven by an open-end or adjustable wrench |
| Materials | Stainless steel 301 / 303 / 304 / 304L / 316 / 316L / 410 / 416 / 17-4PH · carbon steel 1045 / 1215 / 12L14 · alloy steel 4130 / 4140 · aluminium 2024 / 5052 / 6061 / 7075 · brass · bronze · copper · titanium |
| Finishes | As machined · black oxide · zinc plating · nickel plating · chrome plating · anodizing · passivation (through our vetted partner network) |
| Precision | ±0.01 mm on features that locate, seal or fit; ISO 2768-m for general dimensions |
| Marking | Head marking, grade marking or your own identification mark per drawing |
| Documents | Material certificate (MTR) with every batch, plus pre-shipment photos before dispatch |
| MOQ | From 50 pieces per type and material · samples from 1 piece |
| Sample lead time | 5–10 days |
| Production lead time | 25–35 days after sample approval |
| Quote | Within 24 hours, with DFM feedback |
Standard dimensions
Metric hex head bolts and screws — nominal dimensions (ISO 4014 / ISO 4017)
| d | Pitch (mm) | s (mm) | k (mm) | e (mm) |
|---|---|---|---|---|
| M5 | 0.8 | 8 | 3.5 | 8.79 |
| M6 | 1.0 | 10 | 4 | 11.05 |
| M8 | 1.25 | 13 | 5.3 | 14.38 |
| M10 | 1.5 | 16 | 6.4 | 17.77 |
| M12 | 1.75 | 18 | 7.5 | 20.03 |
| M16 | 2.0 | 24 | 10 | 26.75 |
| M20 | 2.5 | 30 | 12.5 | 33.53 |
| M24 | 3.0 | 36 | 15 | 39.98 |
| M30 | 3.5 | 46 | 18.7 | 50.85 |
| M36 | 4.0 | 55 | 22.5 | 60.79 |
d = nominal thread diameter · s = width across flats · k = head height · e = width across corners. Nominal values; your drawing always takes precedence.
Other bolts we manufacture
See all 179 part types →
Send us the drawing
We reply within 24 hours with DFM feedback, a process route and a price. Samples from 1 piece, production from 50 pieces, shipped from Qidong City, Jiangsu Province, China.
Request a quote