Does anyone know which type of steel was originally specified for the CAT12 shear-pin? (tensile strength, yield strength, HRB value)? I'm a bit taken back that I'm unable to find this information anywhere on the internet. Even a Grade-2 bolt has a minimum yield strength of 57 ksi, which is quite a bit more than ordinary A36 hot-rolled steel. Please help?
6D1754?
I think it's 1B676 for an 8T? So is the original part an actual pin (clevis pin), or a threaded bolt? Shopping for clevis pins, the typical hardness for non-heat treated steel pins are HRB-63, which equates to about 50 ksi tensile strength (basically ordinary strength low-carbon mild steel that's been coldworked a bit - similar to Grade-2 bolts). Stainless clevis pins are HRB-80 alloy 18-8, which yields around 35 ksi with tensile around 75 to 80 ksi (typical for high ductility 300 series). I don't believe the stock pins are stainless . . .. ? Heat-treated clevis pins are HRC-25, which is similar to a Grade 5 bolt. There is almost a 3-times increase in shear strength between the non-heat treated clevis pins and the heat-treated ones. I'm assuming the standard non-heat-treated clevis pins would most closely match the OEM part. . . . . ?
1B0676 is called out as being a carbon steel. Spec speaks thusly - "Shallow case-hardened low-strength steel pins and dowels with high wear resistance but low impact resistance due to highly resulfurized steel allowed by this class. Minimum shear strength of the case is 1000 MPa and of the base core material 200 MPa." Regarding the shape it is a headed clevis pin that apparently can have either a circlip groove or a hole for a split pin at the opposite end to the head.
Control Tower shear pin for 8Txxxx
Very interesting. . . . . They put a stress-riser in it - to encourage the onset of shear.
I apricate the help. I was hoping to turn my own on the lathe, but I'm not interested in attempting to case-harden pins at home. 1000 MPa equals 145 ksi on the case-hardening, and 200 MPa equals 29 ksi core. How do they case harden these? Nitride bath? A fast hit with high frequency induction. Who knows? Looks like I'll be buying the proper pins from CAT. Thanks again (I really do appreciate the knowledge sharing).