PERFECT ENGINEERING COBuying Guide
How to Order Bolts & Screws Correctly
Most wrong deliveries come from an incomplete enquiry. Send these details once and you'll get the right part, the right make and an accurate quote the first time.
The 7 details every enquiry needs
- Product and standard — e.g. hex bolt DIN 931 (half thread) or DIN 933 (full thread), socket head cap screw DIN 912, CSK screw DIN 7991, shoulder screw DIN 7379.
- Diameter and thread pitch — e.g. M12 × 1.75. If you don't mention the pitch, standard coarse pitch is assumed. Say “fine pitch” (e.g. M12 × 1.25) or BSW / UNC if you need it.
- Length — in mm, measured the right way (see below).
- Grade / material — 8.8, 10.9, 12.9, or stainless SS 304 / SS 316.
- Finish — black (self colour), zinc plated, hot-dip galvanized, zinc flake, etc.
- Make — TVS/Sundaram Fasteners, Unbrako, LPS, or “any genuine make” if you're flexible on brand.
- Quantity — in pieces, or in boxes if you want full standard packs.
How to measure length
- Hex bolts, allen bolts (SHCS), button head screws: measure from under the head to the tip.
- Countersunk (CSK) screws: measure the overall length, including the head.
- Shoulder screws: the length is the shoulder length — from under the head to where the thread starts.
- Studs and threaded rods: overall length, end to end.
Examples of a complete order line
| What you need | How to write it |
|---|---|
| Hex bolt, full thread | M12 × 1.75 × 50 hex bolt, DIN 933, Gr. 8.8, zinc plated, TVS/Sundaram Fasteners — 200 pcs |
| Allen bolt | M8 × 30 socket head cap screw, DIN 912, 12.9, black, TVS — 1 box |
| CSK allen screw | M6 × 25 CSK screw, DIN 7991, 12.9, black — 200 pcs |
| Shoulder screw | 10 × M8 × 30 shoulder screw, DIN 7379, 12.9 — 20 pcs |
| B7 stud set | M16 × 150 stud, ASTM A193 B7, with 2 nos 2H nuts, PTFE coated — 50 sets |
| Nylock nut | M10 nylock nut, DIN 982, Gr. 8, zinc plated — 500 pcs |
Tips that save time
- Send a photo of the old bolt next to a ruler, or the drawing / BOM, if you're not sure of the standard.
- For repeat OEM orders, share your part list once — we'll keep it on file and quote against it each time.
- Mention if you need test certificates or a specific make for approval.
FAQ
Common questions
What does M12 × 1.75 × 50 mean?
M12 is the thread diameter (12 mm), 1.75 is the thread pitch in mm (standard coarse for M12), and 50 is the length in mm.
Do you supply small quantities?
Yes. We supply both full boxes for OEM production and loose pieces for maintenance, subject to stock.
Need help choosing?
Send us the size, grade and quantity on WhatsApp and we'll recommend the right part and quote the same day.