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500 RMS Serrations per inch- Machinist help?

SSMachine89

Plastic
Joined
Aug 13, 2014
Location
Tampa
I am having a heck of a time finding an answer, and am hoping someone here with machining background will be able to help. How many grooves/serrations would be within a 1" span on a 500 RMS Finish? What would an acceptable amount of grooves per 1" if the surface finish was a 250-500 RMS? Any help is greatly appreciated... my knowledge here is limited.
 
I am having a heck of a time finding an answer, and am hoping someone here with machining background will be able to help. How many grooves/serrations would be within a 1" span on a 500 RMS Finish? What would an acceptable amount of grooves per 1" if the surface finish was a 250-500 RMS? Any help is greatly appreciated... my knowledge here is limited.
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500 grooves per inch is .002" per groove ??
 
RMS has nothing to do with number of grooves per inch, it's about the height of the grooves. It's the Root Mean Squared (RMS) calculation average deviation of groove height from the average line. Generally speaking though, two cuts with the same depth of cut but at two different feed rates, the cut with the slower feed rate will have a better RMS finish.
 
Toolroomguy provided a decent link; as Econdron notes, the RMS value for surface finish is an averaging calculation. Machinery's Handbook also has good descriptions of surface finish definitions and calculations.

Surface roughness - Wikipedia
 
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500 grooves per inch is .002" per groove ??


So a 16 is .0625/groove?




Generally speaking though, two cuts with the same depth of cut but at two different feed rates, the cut with the slower feed rate will have a better RMS finish.

The lower feedrate will yield a lower peak to your valley.
The actual DOC is irrelivent, save for the sake of induced chatter in the surface as well...



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Think Snow Eh!
Ox
 
its interesting a owner doesn't know what RMS is. That's first year stuff at votech. Me consultant had a pretty cool calculator that would figure your feed and speed out to get the required RMS on a piece of material. I no longer have it at my disposal since I only ever had to put a 500 Rms surface on flanged fittings for the guberment jobs. I am sure the machinist hand book has it is as well.
 
27 "grooves" per inch. Or stick a .015" tnr insert in a dnmg holder in a lathe parallel to ways a feed of .037ipr and make a .005" face cut. Just a hair coarser than a Crosby valve standard flange serration. If you use a different tool, make sure the tool has plenty of relief on the back side of the insert so as not to "wipe" the serration.
have fun
i_r_
 
I am having a heck of a time finding an answer, and am hoping someone here with machining background will be able to help. How many grooves/serrations would be within a 1" span on a 500 RMS Finish? What would an acceptable amount of grooves per 1" if the surface finish was a 250-500 RMS? Any help is greatly appreciated... my knowledge here is limited.

You will need a point of reference. To me it looks like you are machining sealing surfaces particularly flange faces?? Check ASME B16.5 or some pipe flange web pages for info. Do you want a formula for machining to a surface finish?

First off you need to know the tool radius depth or point angle depth and are you looking for spiral rings or concentric rings?

You is facing or turning? How will you measure, by counting? you should get about 13 grooves per inch and be about .002-.005 deep between grooves but hell you ain't got a point of reference and it is not just how many effing grroovveess per inch. You gotta know depth and radius and point. If I was you man I would listen to that guy at work that's trying to help you or if he aint there then hit the books man. This is a bit more cerebral trade then we thought when we first started out.
 
If I was you man I would listen to that guy at work that's trying to help you or if he aint there then hit the books man. This is a bit more cerebral trade then we thought when we first started out.


I guess _ in all honesty, maybe we should all quit posting questions here and all just hit the books... At least we should be able to keep the "My Shop" board - wouldn't'cha think? No real questions posed there, just "This h'yah's what I got." for the most part...

:scratchchin:


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Think Snow Eh!
Ox
 
If you know the tooltip geometry and have RMS value, then the "valleys per inch" can be calculated. Of course when assuming there are no other disturbances.
 








 
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