Metric. Imperial.
Bolts. Screws.
Threading basics.
Threading and fastener reference. Metric vs imperial threads, bolt vs screw, fastener selection. Engineering basics for assembly.
Key principles.
M3-M50
Metric coarse and fine. ISO 261 standard.
UNC, UNF
UNC coarse, UNF fine. ANSI B1.1 standard.
Use definition
Bolt: tightened with nut. Screw: threads in mating part.
2 standard
Class 2 most common. Class 3 precision.
5.8 mid, 12.9 high
Metric grades. SAE J429 grades 1-8 imperial.
Corrosion
Zinc, nickel, hot-dip galvanized for corrosion resistance.
FAQ
Metric vs imperial?
Metric standard worldwide. Imperial in US automotive, industrial. Each has standards.
M3-M16 most common?
M3 (3mm), M4 (4mm), M5 (5mm), M6 (6mm), M8 (8mm), M10 (10mm). Default sizes.
Strength selection?
Grade 5.8 (low strength), 8.8 (mid), 10.9 (high), 12.9 (highest). Per load.
Anti-rotation features?
Thread lockers (Loctite), nylon-locked nuts, helicoils. Per service requirement.
Thread engagement length?
1.5-2× diameter for full thread strength. 1× minimum.
Standard vs custom?
Standard cheap, available. Custom: longer lead time, premium cost. Use standard when possible.
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