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M3-0.5 X 6 Hex Bolt
QS Fastener: M3-0.5 X 6 Hex Bolt
Name: M3-0.5 X 6 Hex Bolt
Standard: DIN 933
Material: 304
Size: M3-0.5
Lenght: 6 mm
Surface: Natural color
Standard: DIN 933
Material: 304
Size: M3-0.5
Lenght: 6 mm
Surface: Natural color
Quantity
M3-0.5 X 6 Hex Bolt, fully threaded to DIN 933, is made from austenitic SS304 stainless steel. It withstands ≥ 72 h salt-spray corrosion and delivers a single-piece tensile load of 4.2 kN. The 6 mm nominal length exposes 1–2 threads after tightening, making the M3-0.5 X 6 Hex Bolt ideal for miniature enclosures, PCB brackets and other precision assemblies. Supplied in natural finish (no plating), it is RoHS-compliant and can be passivated a second time for extra corrosion resistance. Every lot is 100 % checked with GO/NO-GO gauges and torque-consistency tests to guarantee zero jamming in automated lines.
Fastener galling (cold-welding) in stainless steel arises from the FCC lattice of austenitic grades: numerous slip systems and low hardness (HV 180–220) promote adhesive wear under high thread pressure. Using the miniature M3-0.5 X 6 Hex Bolt as an example, galling can be prevented only by controlling four factors simultaneously: design, surface, lubrication and installation.
1. Length selection
Bolt nominal length L = clamp thickness t + nut height H + 1.5 P (P = pitch). For the M3-0.5 X 6 Hex Bolt clamping a 3 mm plate and a nut height of 2.4 mm, L ≥ 3 + 2.4 + 0.75 = 6.15 mm; the standard 6 mm length is therefore perfect. After tightening, 0.75 mm remains exposed, ensuring ≥ 6 engaged threads while preventing bending stress from an over-length M3-0.5 X 6 Hex Bolt.
Bolt nominal length L = clamp thickness t + nut height H + 1.5 P (P = pitch). For the M3-0.5 X 6 Hex Bolt clamping a 3 mm plate and a nut height of 2.4 mm, L ≥ 3 + 2.4 + 0.75 = 6.15 mm; the standard 6 mm length is therefore perfect. After tightening, 0.75 mm remains exposed, ensuring ≥ 6 engaged threads while preventing bending stress from an over-length M3-0.5 X 6 Hex Bolt.
2. Strength matching
ISO 3506 specifies that grade A2-70 M3-0.5 X 6 Hex Bolt has Rm = 700 MPa and Rp0.2 = 450 MPa; a matching A2-70 nut provides proof load 700 MPa × As (stress area 5.03 mm²). If an A2-50 nut (500 MPa) is used, the safety margin drops by 29 % and the M3-0.5 X 6 Hex Bolt is prone to overload galling. Always pair fasteners of the same property class.
ISO 3506 specifies that grade A2-70 M3-0.5 X 6 Hex Bolt has Rm = 700 MPa and Rp0.2 = 450 MPa; a matching A2-70 nut provides proof load 700 MPa × As (stress area 5.03 mm²). If an A2-50 nut (500 MPa) is used, the safety margin drops by 29 % and the M3-0.5 X 6 Hex Bolt is prone to overload galling. Always pair fasteners of the same property class.
3. Surface and cleanliness
Keep thread roughness Ra ≤ 3.2 µm to reduce galling risk. If stored M3-0.5 X 6 Hex Bolt threads are nicked, polish with 400-grit paper along the helix until the GO gauge passes freely. Degrease threads with acetone or anhydrous ethanol to remove chloride ions (≤ 25 ppm) and solid particles that can initiate pitting and galling.
Keep thread roughness Ra ≤ 3.2 µm to reduce galling risk. If stored M3-0.5 X 6 Hex Bolt threads are nicked, polish with 400-grit paper along the helix until the GO gauge passes freely. Degrease threads with acetone or anhydrous ethanol to remove chloride ions (≤ 25 ppm) and solid particles that can initiate pitting and galling.
4. Perpendicular driving and lubrication
When using a precision open-end wrench or socket, keep the tool face perpendicular to the axis of the M3-0.5 X 6 Hex Bolt within 1°. A 5° tilt increases flank contact width by 4.3 % and raises local contact stress σH by ~9 %, accelerating wear. Apply a full-thread dry film of MoS₂ (μ = 0.08–0.12) or a PTFE-based paste to cut friction torque by 25 %–40 %.
When using a precision open-end wrench or socket, keep the tool face perpendicular to the axis of the M3-0.5 X 6 Hex Bolt within 1°. A 5° tilt increases flank contact width by 4.3 % and raises local contact stress σH by ~9 %, accelerating wear. Apply a full-thread dry film of MoS₂ (μ = 0.08–0.12) or a PTFE-based paste to cut friction torque by 25 %–40 %.
5. Torque control
Safe torque T = K · F · d, where K is the overall friction factor (0.12–0.15 lubricated, 0.18–0.21 dry), F is preload (1.1 kN for A2-70 M3-0.5 X 6 Hex Bolt) and d = 3 mm. With lubrication (K = 0.13): T ≈ 0.13 × 1.1 N·m × 3 mm = 0.43 N·m; dry conditions raise this to 0.7 N·m. Use a ±3 % precision torque driver: tighten the M3-0.5 X 6 Hex Bolt in two steps—50 % torque to remove clearance, then 100 % final torque—pausing 2 s every 90° to allow stress relaxation and avoid torque spikes that cause micro-welding.
Safe torque T = K · F · d, where K is the overall friction factor (0.12–0.15 lubricated, 0.18–0.21 dry), F is preload (1.1 kN for A2-70 M3-0.5 X 6 Hex Bolt) and d = 3 mm. With lubrication (K = 0.13): T ≈ 0.13 × 1.1 N·m × 3 mm = 0.43 N·m; dry conditions raise this to 0.7 N·m. Use a ±3 % precision torque driver: tighten the M3-0.5 X 6 Hex Bolt in two steps—50 % torque to remove clearance, then 100 % final torque—pausing 2 s every 90° to allow stress relaxation and avoid torque spikes that cause micro-welding.
By rigorously following the five measures above, the galling probability of the M3-0.5 X 6 Hex Bolt is reduced from 15 % to < 0.5 %, while service life is extended by 3–5 times.
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