Just 'Cuz Robotics
4mm x 35mm Alloy Steel Class 12.9 Shoulder Bolts, 10 Pack
4mm x 35mm Alloy Steel Class 12.9 Shoulder Bolts, 10 Pack
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The minimum ultimate tensile strength of the Grade 12.9 Metric Bolts is about 1242 Mpa or 180,000 PSI, making them the highest grade of bolts produced.
These bolts are a major upgrade compared to the common stainless steel ones you’ll find in this size. They had to be custom ordered in batches of at least 500 as this length is a bit unusual, but the cost is well worth it! These should be about 2.5 times stronger than stainless steel. CAD Here.
These shoulder bolts have a precision ground bearing surface hardened to 39-44 HRC and are perfect for use with 4mm inner diameter bushings, bearings, and more.
- Shoulder Diameter: 4mm (actual 3.95-3.98mm)
- Shoulder Length: 35mm
- Shoulder Surface Roughness: 0.8 micro-meter (32 micro-inch) Ra
- Head Diameter: 7mm max, 6.78mm min
- Head Height 3.5mm max
- Thread: M3x0.5, 6mm length max
- Drive: 3mm Hex
- Weight: ~4.4g (0.156oz) each
This was a no brainer, bought these steel shoulder screws right before a tournament to replace 18-8 Stainless Steel shoulder screws. More than double the tensile strength, higher hardness rating, and precision ground to fit in my servo arm these steel shoulder bolts should be a necessity. I managed to last five fights with a single should screw and only left with a negligible bend in the threaded section; screw is still functional.
