Screws

Screw families: where the thread does the work

Machine screws carry a uniform thread over the whole threaded length and are meant for a nut or a tapped hole; wood screws are the visual counterpoint — their threads taper toward the point, which is why the two are not interchangeable. Self-tapping screws cut or form their own mate in the base material, and the type letter is a thickness rating: Type A runs in thin sheet metal (roughly 0.015–0.050 in thick), while Type B — larger root diameter, finer pitch — covers the 0.050–0.200 in range plus non-ferrous castings and plastics. Thread-forming, thread-cutting and thread-rolling variants differ in whether they displace or remove material, and which chip clearing and tightening-torque behaviour follows; the self-tapping screw types guide under Related knowledge tabulates that split.

Self-drilling screws (TEK-pattern) add the drilling step: a drill-bit point with flutes drills, taps and fastens in one operation with no pilot hole. The TEK number is a point-length rating matched to metal thickness — the common 25-to-16-gauge sheet runs a TEK 3, 14 gauge and thicker needs TEK 4–5, and the longest points are the ones used on structural steel. Wood screws and the family selection logic by base material are compared in the screw family selection guide under Related knowledge.

Head style and drive: appearance, clearance, flushness

Head choice is set by the finished surface the assembly needs. Round and pan heads stand proud of the surface and leave room for a washer under them; flat countersunk heads sit flush for a snag-free fit where the assembled part meets another surface. Countersinking also costs head height, so a flush head trades clamping bearing area for profile — where both matter, the hex-vs-socket-head comparison under Related knowledge shows the trade-off on a real joint.

Drive choice follows the assembly tooling and the torque the joint sees: slotted and Phillips remain the two most common machine-screw drives, with Torx and hex socket available where higher torque transmission matters and the RFQ names the tooling. If you are matching an existing assembly, name the drive you have; if you are designing new, name the drive on the inquiry so the quote confirms head style and tooling together.

Materials and case hardness

Machine screws span the widest material range of the family — steel, stainless steel, brass and nylon are all standard — because the joint, not the driving process, picks the strength. Tapping and self-drilling screws are the opposite: the point has to stay harder than the base material it drives into, so they are case-hardened carbon steel (surface hardness Rockwell C45 minimum with a C28–38 tempered core; self-drilling points harder still at C52–58 surface and C32–40 core) or 410 stainless, which heat-treats to about Rockwell C40 while keeping corrosion resistance.

This hardness split drives the coating decision: hardened tapping and self-drilling screws carry the hydrogen-embrittlement constraints of any electroplated hardened part, so zinc-flake and mechanical-deposition systems are preferred at the high-hardness end. The coating systems and their selection logic are the surface finishes family, one level up from this page.

Operating limits and thread matching

Two limits end most misapplications. First, machine-screw threads must match the pre-tapped hole exactly — diameter and pitch together — because the mating hole is typically tapped for one specific size and thread type, so a thread "close enough" is not quotable. Second, self-drilling screws are a metal-to-metal fastener: the drill point cuts a hole nearly the size of the screw's threaded portion, which gives the threads nothing to bite in wood — wood-to-metal work needs a reamer-style (winged) screw or a separate pilot, and the sheet-thickness windows in the first section bound how far each tapping type can reach.

Within those limits the supply range runs to M36 / 1-1/2" diameter and 300 mm length across metric and inch threads; sizes, drives or head combinations outside the standard list are confirmed at quotation rather than assumed.

Documents

Shipments are backed by Mill Test Certificate (MTC), Dimensional Report, Salt Spray Test Report on request, with full batch traceability from raw material to finished product. Quality management follows the owner-confirmed compliance list: ISO 9001:2015, RoHS, REACH. Exact document sets are confirmed on the order.

Quotation

• The fastener family (Screws) plus the standard designation from your drawing — DIN / ISO / JIS / ASTM / ANSI, or a drawing for custom parts.
• Size (diameter and length), thread type (metric or inch), property class or grade, and coating or finish.
• Quantity per size and your target delivery date.
• Destination country, and any required documents (for example a mill test certificate) so the quote includes them.

Sample & supply

Minimum order quantity is 10,000 pieces. Stock items run 3–7 days. Quantities or variants outside the standard range are confirmed at quotation.

Storage & shipping

Parts are packed for export and shipped factory-direct to buyers in Europe, Asia, the Americas and the Middle East. Store fasteners dry and protected until installation, and keep coated parts in their packaging until use; specific packing and preservation requirements can be stated on the order and confirmed at quotation.

Which drive type should I choose — hex socket, Phillips, slotted, Torx or square?

All five drives are in the quoted range. The choice usually follows the assembly tooling you already run and the torque the joint needs; hex socket and Torx carry higher torque with less cam-out than slotted. If you are replacing an existing part, match the drive you have. If you are designing new, name the drive on the RFQ and the quote confirms tooling and head style together.

What is the MOQ and lead time for screws?

The minimum order quantity is 10,000 pieces. Stock items ship in 3–7 days. Head styles or drive combinations outside the standard list are confirmed at quotation.

What does a quotable screw inquiry need to state?

Head style (hex socket cap, countersunk, button head), screw type (machine, self-tapping or set), drive, diameter and length, thread type, material and coating, quantity per size, and destination country. For self-tapping screws, naming the base material thickness helps the quote confirm the right thread form.