I had gotten into a heated debate on another forum about some aftermarket action screws for CZ 455's. The people offering the screws claim they have the same bevel angle under the head as the factory originals but they dont as you can see in this picture...
Shadowgraph at my work shows the originals as 90 deg and the aftermarket ones as 120 deg.
Now these screw heads mate to a fairly thin metal trigger guard that has a 90 deg chamfer in it to match the original factory screws. The aftermarket screws engage only a small portion of this chamfer at the outer diameter. The original screws are T30 Torx and the aftermarket screws are regular 4mm hex drive.
I was severely chided and given infractions for citing references (that were deleted by mods) to the fact that Torx drives have numerous advantages over Hex, and that matching the chamfers is critical for reasons of strength, achieving consistant torque, and eliminating excess wear or damage on the parts.
As a side note, these screws are normally torqued to 20-30 in/lbs at the most and come nowhere near their limits (6mmX1) of over 100 in/lbs for shearing or other strength issues.
I am a machinist/tool and die maker (certified) that has worked with fasteners, automation design and testing for 30 years and my take on it is that there is no benefit from mismatched bevels and an inferior drive. The aftermarket screws claim to be stronger material wise, but again, is this a good thing when you would rather have a softer screw thread strip then the female thread in your action. (there is limited engagement on the threads, aprox 1X thread diameter). Both screws are similar in the tiny tool radius where the bevel begins so this was not a determining factor of strength.
What are your opinions on the aftermarket screw being "better" then the originals in these two regards. Personally I think the mods and fellows pushing this product are full of doo doo and don't know what they are talking about. One even claims to have tested them and found the factory screws inferior, but never even noticed the difference on the bevels under the head.
Shadowgraph at my work shows the originals as 90 deg and the aftermarket ones as 120 deg.
Now these screw heads mate to a fairly thin metal trigger guard that has a 90 deg chamfer in it to match the original factory screws. The aftermarket screws engage only a small portion of this chamfer at the outer diameter. The original screws are T30 Torx and the aftermarket screws are regular 4mm hex drive.
I was severely chided and given infractions for citing references (that were deleted by mods) to the fact that Torx drives have numerous advantages over Hex, and that matching the chamfers is critical for reasons of strength, achieving consistant torque, and eliminating excess wear or damage on the parts.
As a side note, these screws are normally torqued to 20-30 in/lbs at the most and come nowhere near their limits (6mmX1) of over 100 in/lbs for shearing or other strength issues.
I am a machinist/tool and die maker (certified) that has worked with fasteners, automation design and testing for 30 years and my take on it is that there is no benefit from mismatched bevels and an inferior drive. The aftermarket screws claim to be stronger material wise, but again, is this a good thing when you would rather have a softer screw thread strip then the female thread in your action. (there is limited engagement on the threads, aprox 1X thread diameter). Both screws are similar in the tiny tool radius where the bevel begins so this was not a determining factor of strength.
What are your opinions on the aftermarket screw being "better" then the originals in these two regards. Personally I think the mods and fellows pushing this product are full of doo doo and don't know what they are talking about. One even claims to have tested them and found the factory screws inferior, but never even noticed the difference on the bevels under the head.
