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Surface Roughness - What is difference between Ra, Rmax & Rt

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  #1  
Old 25th July 2007, 04:48 AM
reddy

 
 
Posts: 1
Question Surface Roughness - What is difference between Ra, Rmax & Rt

Can anybody help me in differentiating surface roughness measurment values in Ra,Rmax and Rt. In what conditions we use Rmax.

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  #2  
Old 25th July 2007, 06:33 AM
Ted Schmitt's Avatar
Ted Schmitt

 
 
Posts: 667
Re: Surface Roughness - What is difference between Ra, Rmax & Rt

Quote:
In Reply to Parent Post by reddy View Post

Can anybody help me in differentiating surface roughness measurment values in Ra,Rmax and Rt. In what conditions we use Rmax.
Welcome to the Cove !

Average roughness (Ra). The average height of the bumps on a surface, measured in micrometres or microinches.

Rt = is the difference between the highest peak and the lowest valley

Rmax = is the highest peak
Thank You to Ted Schmitt for your informative Post and/or Attachment!
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  #3  
Old 25th July 2007, 07:57 AM
Stijloor's Avatar
Stijloor

 
 
Posts: 14,654
Re: Surface Roughness - What is difference between Ra, Rmax & Rt

Quote:
In Reply to Parent Post by reddy View Post

Can anybody help me in differentiating surface roughness measurment values in Ra,Rmax and Rt. In what conditions we use Rmax.
Hello reddy,

Here is some info.

http://www.mfg.mtu.edu/cyberman/qual...ace.html#para2

Hope this helps.

Stijloor.
  #4  
Old 25th July 2007, 08:22 AM
AndyN's Avatar
AndyN

 
 
Posts: 7,895
Question Re: Surface Roughness - What is difference between Ra, Rmax & Rt

Surface finish is often called out for two reasons:-

Functional performance, such as in a sealing ring application, bearing surfaces;

Appearance, where the finish has to look or feel smooth, etc. or requires further processing

It would be helpful to know how your organization is applying Ra to it's products.
  #5  
Old 25th July 2007, 10:38 AM
tenaiwa

 
 
Posts: 20
Re: Surface Roughness - What is difference between Ra, Rmax & Rt

Hello,
It depends on your application
Pls consider also
function surface vs No function
friction->rolling or sliding
clearance fit or press fit
dimension presion of product
stress/load exist or not (corner,concave angle..)

hope it helps a little.
  #6  
Old 25th July 2007, 10:58 AM
harry

 
 
Posts: 6,277
Re: Surface Roughness - What is difference between Ra, Rmax & Rt

Also have a look at here, here and here.

Last edited by harry; 25th July 2007 at 07:47 PM. Reason: fix link
  #7  
Old 25th July 2007, 11:51 AM
Stijloor's Avatar
Stijloor

 
 
Posts: 14,654
Re: Surface Roughness - What is difference between Ra, Rmax & Rt

Quote:
In Reply to Parent Post by harry View Post

Also have a look at these threads.

Hello Harry,

Somehow, the link did not work.

Stijloor.
Thanks to Stijloor for your informative Post and/or Attachment!
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