What parameters are needed for fasteners to be quoted

A fastener quotation is only as accurate as the data behind it. Hex head bolts, stud bolts, nuts and washers are rarely bought as isolated parts: together they form the fastening set of a bolted joint that also clamps the flange gaskets and keeps the seal under pressure, so one missing parameter turns into a price deviation, a late delivery or a quality dispute. The checklist below is what a manufacturer needs to see before it can price a line item.

Product Type, Standard and Size

Start with the exact product name and type: hex head bolt, socket head cap screw, stud bolt, countersunk head bolt, threaded rod, nut or washer. Special features — a drilled hole, a groove, a locking element or a serrated bearing face — change the tooling and the process route, so state them in the inquiry. Stud bolts are usually ordered for pipe flanges, and their length is measured end to end, while bolt length is taken under the head; mixing the two conventions is a frequent cause of non-conforming parts.

• Standard number — DIN 933, DIN 931, ASTM B18.2.1 or the drawing reference. Dimensions, tolerances and mechanical requirements differ between standards even at the same nominal size.
• Diameter and length — M12, 1/2 in and similar; state whether length means thread length or overall length.
• Across-flats width, head height or thickness, and shank type: fully threaded or partially threaded.
• Thread form and tolerance class — metric coarse or fine, inch coarse or fine, 6g, 6H.
• Drawings or samples for every non-standard size.

Material Grade and Mechanical Properties

The material grade drives price and delivery more than any other line of the inquiry. Give the grade and the property class together — A2-70, B7, Class 8.8 — and add any chemical composition or mechanical test requirement the order has to meet.

Table 1. Material groups and the data a quotation has to state.

In corrosive or hot service, name the alloy instead of a generic description: Monel 400 for seawater, acids and alkalis, Inconel 600/718 for oxidation resistance and high-temperature strength, Hastelloy C276 for aggressive media, and 17-4PH or Incoloy 901 where precipitation hardening is required.

Surface Treatment and Service Conditions

Coatings protect against corrosion and, in some cases, change friction and appearance: zinc plating in blue-white, yellow chromate or black, hot-dip galvanizing, Dacromet, phosphating, black oxide, nickel plating, passivation for stainless steel and PTFE coating.

• State the required corrosion life and any salt spray test hours instead of the coating name alone.
• High-strength fasteners pick up hydrogen during acid pickling and electroplating, so specify hydrogen removal after plating for property classes such as 10.9 or B7.
• Describe the service: seawater, strong acids or alkalis, high temperature and pressure, or outdoor exposure. The environment, not the catalogue, should decide the coating.
• Mention lubrication, pre-assembly of screw, washer and nut, and head marking only if the assembly line needs them.

Quantity, Packaging and Delivery Data

Commercial data completes the picture and should travel with the technical data: quantity tier — sample, small batch, pilot run, mass production — plus an annual forecast where one exists, packaging form (bulk in bags or bundles, boxes, cartons, pallets) and whether labels, barcodes, anti-rust paper or vacuum packing are required. Add the agreed Incoterm (FOB, CIF or similar), the destination and the point from which the production cycle runs: order confirmation, receipt of the advance payment or complete documentation.

Frequently Asked Questions

How is the length of a stud bolt measured?

A double end stud is measured end to end over the full length, while a hex head bolt is measured under the head. When the stud is partly threaded, state both thread length and overall length, and attach a drawing for special take-up conditions.

What is the difference between coarse and fine thread?

Metric coarse thread is the default for general assembly; fine thread suits thin walls, precise adjustment and higher vibration resistance. The inch system uses the same coarse/fine distinction, and the tolerance class — 6g for external threads, 6H for internal threads — controls fit and machining cost.

When must a Material Test Certificate be supplied?

Whenever the part has to be traceable — pressure equipment, oil and gas, offshore or power service — state that a mill certificate or certificate of conformity is required and define the test methods and acceptance values, for example tensile strength or hardness.

Which surface treatment suits high-strength fasteners?

Electroplated zinc is the standard option, but acid pickling and plating introduce hydrogen; for property classes 10.9 and B7 specify hydrogen removal after plating and, in aggressive media, a top coat or PTFE. Black oxide and passivation add no embrittlement risk but protect less against corrosion.