Machinist question.

[Goldeneagle]

We have a bit of a disagreement here. We have a part that calls out for a circular finish. Using a profilometer, do you check across the grain or position it like you would a stylus on an album?

[Monark]

We always check our recip compressor liners across the grain. Profilometer measures highs & lows on surface roughness. A circular finish sounds like a pipe flange to give a gasket something to bite in to.

[Sean]

You are way above my pay grade of doing oilfield sprockets and gears.

[Jaybo31]

Is the circle part a dynamic part that moves across a seal or a seal moves across it?
If so you better check it linear across the grain.

[taco1979]

Across the grain to get a true high/low reading and average, but as someone else stated not sure what a circular pattern is aside from the grooves when machining pipe flanges

[Goldeneagle]

Across the grain to get a true high/low reading and average, but as someone else stated not sure what a circular pattern is aside from the grooves when machining pipe flanges

These are lathe parts. The finish is called out on the face of the part.

[trhunter]

Across the grains. I assume the finish is a RMS?

[kck]

I’d say take the measurement radially (obviously being a turned part) from outside to inside to centerline if your profilometer has that much stroke. If not you may take multiple readings to find the worst finish. I’ll check with my QC gurus at the shop as well and make sure they concur.

[miket]

I dont know. Good question. I go perpendicular to the feedlines because naturally thats where it should be the worst ( unless you have other issues ). In the end, it is whatever gives you the worst reading. ( in my experience ). It does sound like maybe they just want to make sure the surface is turned rather than milled.

[Goldeneagle]

I dont know. Good question. I go perpendicular to the feedlines because naturally thats where it should be the worst ( unless you have other issues ). In the end, it is whatever gives you the worst reading. ( in my experience ). It does sound like maybe they just want to make sure the surface is turned rather than milled.

I was taught that a circular finish was checked as close to circular you can get. Like a stylus on an album. Been doing it like this for over 30 years. Now all of the sudden QC says it is wrong. I've been researching it all day and haven't found anything that straight up says one way or the other.

[miket]

I was taught that a circular finish was checked as close to circular you can get. Like a stylus on an album. Been doing it like this for over 30 years. Now all of the sudden QC says it is wrong. I've been researching it all day and haven't found anything that straight up says one way or the other.

Certainly cant argue with you on that. I dont know.