Industrial fasteners: grades, sizes and ordering in bulk

Fasteners are small and cheap per piece, which is exactly why they get specified carelessly. But a bolt of the wrong grade in a machine, or a lot with a slightly different thread, can stop a production line or cause a failure. Clear specifications turn fasteners into a routine repeat order instead of a recurring problem.

Size and thread

• Diameter and length — for metric fasteners, written as M10 × 50, for example.
• Thread pitch — standard (coarse) or fine. Mixing them up means parts will not fit.
• Metric or inch — older or imported machines may use inch sizes.
• Head type — hex, socket head (Allen), countersunk, button head, and so on.

If you are replacing an existing part, share a sample or the drawing.

Grade and strength

Bolts come in strength grades, usually marked on the head (for example 8.8 or 10.9 for metric bolts).

• Use the grade your design or machine manufacturer specifies — do not substitute a lower grade to save money.
• Match nuts to bolts of a compatible grade.
• For structural or safety-critical use, ask for test certificates.

Material and coating

• Mild steel and alloy steel for general and high-strength use
• Stainless steel where corrosion resistance matters — food, outdoor, chemical environments
• Coatings such as zinc plating or hot-dip galvanising protect against rust; ask which suits your environment

Standards and consistency

Ask which standard the fasteners follow (IS, DIN or ISO). Standardising on one reduces confusion between lots and suppliers.

Packing and ordering

1. Ask whether prices are per piece, per hundred or per kilogram.
2. Ask how items are packed and labelled — clearly labelled boxes save time on the shop floor.
3. For regular use, agree a monthly schedule or a stock-holding arrangement with the supplier.

Checking what arrives

• Check head markings for grade.
• Measure a few pieces with a gauge.
• Keep lots separate until checked, so a bad lot does not mix with good stock.

Mistakes to avoid

• Substituting a lower grade to save money. The saving is tiny compared with the cost of a failure.
• Mixing lots on the shelf. Keep each lot labelled until it is checked; mixed bins make faults impossible to trace.
• Ordering without drawings or samples. For special or non-standard parts, a drawing or sample avoids a whole wrong batch.
• Ignoring corrosion. Plain steel fasteners in outdoor or wet areas rust quickly; specify the coating or stainless grade upfront.
• No reorder level. Running out of one common bolt size can stop assembly. Set minimum stock levels for your most-used items.

What to include in your enquiry

• Item list with type, size, thread, length and head type
• Grade and material, and coating
• Standard (IS, DIN, ISO) if you follow one
• Quantity per item and whether it is a monthly requirement
• Delivery location and GSTIN

Compare suppliers in industrial supplies, or post your requirement with your item list.