ASME B46.1 Surface Roughness 1

[STrctPono]

I was hoping someone could help me interpret ASME B46.1. I have a set of contract specs that require a bridge bearing stainless steel sliding surface to be polished in accordance with ASME B46.1 maximum surface roughness of 125. I don't have a copy of this publication and have no idea what that correlates to. The AASHTO Bridge Design specs say that sliding bearings should be provided with a surface finish of 8.0 micro-inch RMS or better. I have no idea how this compares to what is being called out for in the specs. Does anybody know if these two are in accordance with each other?

 

[mfgenggear]

Look up standard surface finish
The higher the number the rougher the finish.
250, 125, 63 32 16 6 and finer.
125 or 63 can be a milled or turned
Surface,
An 8 micro is a very fine ground surface and or lapped
All are inspected by means of a surface analyzer.
8 micro or finer are for bearing surfaces.

 

[STrctPono]

Wow! I'm an idiot. Thanks for clarifying that. So basically, the Engineer's Specifications calling for 125 (125 micro inches) is way rougher than what is required per code (8 micro inches)? This is for a bridge bearing with PTFE sliding apparatus.

 

[mfgenggear]

That's odd that code is 8 micro, I would recommend contacting the engineer. Make sure he is not in error.

 

[STrctPono]

Thanks. The target coefficient of friction is 0.05 of the system. I'm certain that the Engineer is in error as it would be pretty par for the course.

 

[SwinnyGG]

Specifying surface finish is a very tricky thing - the various approaches in common use are not interchangeable, and cross-referencing one to another is not straightforward. Before you decide the engineer is in error, you should make sure you understand exactly what the surface finish calls out in the code, and exactly what your engineer is specifying.