Machine Screws
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What are machine screws? Machine screws are precision threaded fasteners designed to secure metal, plastic, composite materials, and other components by threading into a matching nut, tapped hole, or threaded insert. Unlike wood screws or self tapping screws, machine screws feature a uniform diameter and fine, machine cut threads that provide precise, reliable fastening for applications requiring repeatable assembly and disassembly. Machine are available in a wide variety of head styles, drive types, thread sizes, lengths, materials, and finishes to meet the performance requirements of virtually any application. Because they are designed to be removed and reinstalled without damaging the mating threads, machine screws are an ideal choice for applications requiring routine maintenance, servicing, or future disassembly.
Machine Screws
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Standard Machine Screws
Fully machine-threaded screws in a range of head and drive styles for fastening into tapped holes or securing with a nut.
- Phillips Pan Head
- Phillips Flat Head
- Phillips Truss Head
- Phillips Oval Head
- Square Drive Pan Head
- Star Drive Pan Head
- Star Drive Flat Head
- Star Drive Truss Head
- Slotted Pan Head
- Slotted Flat Head
- Slotted Oval Head
- Slotted Truss Head
- Slotted Round Head
- Slotted Binding Head
- Slotted Fillister Head
- Slotted/Phillips Truss Combo Head
- Knurled Thumb Head
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Tamper Proof Machine Screws
Machine screws with security drive styles that resist removal by standard tools, used to deter tampering on public and shared fixtures.
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What Are Machine Screws?
Machine screws are straight, uniform-diameter screws made to mate with a nut or a tapped hole in metal, plastic, or wood with inserts. They are tightened with a driver or socket and are stocked in many head styles, drive types, materials, and finishes to suit production assembly, maintenance, and OEM work.
Common Types of Machine Screws
- Standard machine screws: General-purpose fasteners in pan, flat (countersunk), button, oval, truss, and round heads with slotted, Phillips, combo, Torx/6-lobe, or hex-socket drives.
- SEMS (captive-washer) screws: Pre-assembled with one or more washers under the head for faster, consistent assembly and improved bearing area.
- Tamper-resistant machine screws: Security drives (pin-in Torx, spanner, tri-wing, one-way) to deter unauthorized removal.
- Thread-cutting / thread-forming machine screws: Cut or form mating threads in thin sheet metal or plastics where tapping is impractical.
- Specialty styles: Sidewalk/hurricane-panel bolts, captive panel screws, and floorboard screws for specific applications.
Materials & Finishes
- 18-8 / 304 stainless: dependable corrosion resistance for most indoor/outdoor uses.
- 316 stainless: upgraded corrosion resistance for marine, chloride, and chemical environments.
- Carbon steel, zinc plated: economical and clean appearance for dry interiors.
- Black oxide steel: matte black appearance; light corrosion resistance—use indoors or with protective oil.
- Brass / silicon bronze: non-magnetic, conductive, and corrosion-resistant options for electrical and architectural work.
Sizes, Threads & How to Specify
Order machine screws by diameter × thread × length. Examples: #6-32 × 1″, 1/4″-20 × 2″, M4-0.7 × 20 mm. Inch series use UNC (coarse) or UNF (fine) threads; metric uses ISO pitches (M2–M12 common). Length is measured from under the head to the tip—except countersunk flat heads, which are measured overall.
Where Machine Screws Are Used
- Metal fabrication, enclosures, and sheet-metal assemblies
- Electronics, appliances, HVAC, and automotive service
- Fixtures, furniture, and architectural hardware
- Plastic parts with threaded inserts; wood parts with inserts or T-nuts
Installation Basics
- Confirm the thread size and pitch match the nut or tapped hole.
- For tapped holes, use the correct tap-drill size and full thread depth; for clearance holes, drill per the clearance chart.
- Use washers to protect surfaces or increase bearing area; consider lock washers, prevailing-torque nuts, or threadlocker where vibration is present.
- In plastics or thin sheet, use thread-forming/cutting screws or install threaded inserts for stronger joints.
- Apply appropriate torque—avoid over-tightening, which can strip threads or deform thin materials.
Related Hardware
- Finished machine screw nuts, keps (external-tooth) nuts, flange nuts, nylon-insert lock nuts
- Flat, fender, lock, and finishing washers
- Threaded inserts for plastic/wood, T-nuts, binding posts (sex bolts)