If you buy hex bolts for structural or general engineering work in India, you will see IS 1363 on drawings and purchase orders. It is the Indian Standard for hexagon head bolts, screws and nuts of product grade C, and it is closely aligned with the corresponding ISO standards.
What "product grade C" means
Bolt standards group products into grades A, B and C by how tightly their dimensions and form are controlled. Grade C has the widest tolerances. These are the robust, general-purpose bolts — often called black bolts — used in steel structures, machinery frames and fabrication, where clearance holes are used and extreme dimensional precision is not needed.
Product grade is about tolerances, not strength. Strength is set separately by the property class, such as 4.6 or 8.8, which you specify on your order.
Thread pitch from M12 to M64
IS 1363 bolts use ISO metric coarse threads. For the sizes S A Engineering manufactures, the coarse pitches are:
| Size | Coarse pitch (mm) | Size | Coarse pitch (mm) |
|---|---|---|---|
| M12 | 1.75 | M36 | 4.0 |
| M16 | 2.0 | M42 | 4.5 |
| M20 | 2.5 | M48 | 5.0 |
| M24 | 3.0 | M56 | 5.5 |
| M30 | 3.5 | M64 | 6.0 |
Using the standard coarse pitch means bolts, nuts and tapped holes from different sources fit together. If your drawing calls for a fine pitch, say so explicitly in the enquiry.
Length and thread length
Bolt length is measured from under the head to the end of the bolt. Longer bolts are usually part-threaded: the plain shank sits in the joint and the thread is only as long as the nut and clamping range need. Shorter bolts are often threaded to the head. When you order, state the overall length and, if it matters for your joint, the thread length — S A Engineering makes hex bolts up to 500 mm long.
How to write a clear order line
- Standard and type — for example, hex head bolt to IS 1363
- Diameter × length — for example, M24 × 150
- Property class — for example, 4.6 or 8.8
- Thread length, if not standard
- Finish — plain, oiled or coated
- Nuts and washers per bolt, and quantity
Send that line to our team and we will reply with price and lead time for HS hex head bolts with nuts.
