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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

Regular price $17.50
Regular price Sale price $17.50
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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

Customer Reviews

Based on 4 reviews
Liz M.
Always need more!!!

I've been using these in my antweights for about a year and they're great! I've never experienced meaningful damage to one. I give them to friends regularly to help beef up their designs.

Drew Monteith
Great product for a great price.

These shoulder bolts were going to cost $120ish from McMaster Carr for a quantity of 10… they work perfectly
as dead shafts for my antweight shuffler, and I cannot recommend these enough.

Steven Jack
Very strong

Amazingly resilient. I use those for most of my builds and I've only had one bend one me and my bot took quite a a hit to do that.

Chad Jones
Hardened Steel Beats 18-8 SS Shoulder Screw

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.

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