Engineers Edge
surface finish in RMS Awesome
Post Reply   Engineering Forum
Posted by: JohnsonSignCo

09/15/2004, 11:55:59

Author Profile
eMail author
Edit

We are having a 1/2'' thick aluminum plate sent out for a vertical brush finish applied to it. They want to know what RMS are we looking for. Nobody here knows what RMS is, let alone what to tell them. Can ANYBODY help me?

Thank you in advance for any and all information.

Marsha








Post Reply
Tell a Friend (must be logged in)
Alert Admin About Post
View All   | Next |

 
Share |

Replies to this message

: surface finish in RMS
: surface finish in RMS -- JohnsonSignCo Post Reply Top of thread Engineering Forum
Posted by: moaweh

04/21/2010, 22:41:33

Author Profile
eMail author
Edit

RMA(RA) Stand for Root Mean Square(Roughness Average), it is a term used to measure the roughness of a surface,RMS 63 is a smooth surface finish, RMS 125 is an average manufacturing surface, RMS 25 is a very clean smooth surface finish. There are several tools to use to acomplish such surface finish....
RMS is required usally in the most demanding fluids applications.

Mike A Abuhatoum.







Modified by moaweh at Wed, Apr 21, 2010, 22:43:43


Post Reply
Tell a Friend (must be logged in)
Alert Admin About Post
Where am I? Original Top of thread |   |
Re: surface finish in RMS (Ra)
: surface finish in RMS -- JohnsonSignCo Post Reply Top of thread Engineering Forum
Posted by: Cragyon

09/15/2004, 13:25:16

Author Profile
eMail author
Edit

RMS (Too Mean Square) is a commonly mistaken for Ra (Roughness Average).   Roughness average is a specification which controls the average extremes of the surface irregularities that result from the manufacturing tool used to cut the metal.  These are the mico-scores on the surface of the metal.

Check out the following page http://www.engineersedge.com/surface_finish.htm

 








Post Reply
Tell a Friend (must be logged in)
Alert Admin About Post
Where am I? Original Top of thread | |
Re: surface finish in RMS (Ra)
: Re: surface finish in RMS (Ra) -- Cragyon Post Reply Top of thread Engineering Forum
Posted by: randykimball

09/15/2004, 18:37:07

Author Profile
eMail author
Edit

True.
For those not accustomed to RMS here are some familiar atricles I hope you can relate to. Although RMS (roughness measurement system) is generally used to describe metal cutting surface finish there is no reason not to use it most anywhere you wish.

My cell phone has an RMS of around 32, smoother would make it too slippery.

A song on a long play phono album (for those that member) is around 125.

A magazine cover is about 16.

A business card is between 32 and a 16..

A mirror or window is about 4.

A strip of duck tape feels about 250. By the way, duck tape was named because it would work under water during WW II, .... not from being used as a duct tape as is commonly thought.

The face of a plastic spoon is around 16 to 8.

I haven't spotted a good example of a 500 RMS, But... generally a fairly well done torch cut is about a 500 RMS.

Please realize these items are not actually the RMS I suggest, this is simply a general touch and feel test. They would test much differently. But... this gives you a reasonable and useful set of examples.

As you noticed there is a tendency to use 4, 8, 16, 32, 64, 125, 250, and 500 as common numbers to call out on a product.

-randy-





The worst suggestion of your lifetime may be the catalyst to the grandest idea of the century, never let suggestions go unsaid nor fail to listen to them.

Modified by randykimball at Wed, Sep 15, 2004, 18:39:50


Post Reply
Tell a Friend (must be logged in)
Alert Admin About Post
Where am I? Original Top of thread | |
Re: Re: surface finish in RMS (Ra)
: Re: surface finish in RMS (Ra) -- randykimball Post Reply Top of thread Engineering Forum
Posted by: 993334236

01/12/2007, 11:21:19

Author Profile
eMail author
Edit

RMS actually stands for Root-Mean-Square, a statistical measurement of the square root of the average of the squares of the measurement. The RMS value is generally 11% higher than the Ra value for the same surface roughness.







Post Reply
Tell a Friend (must be logged in)
Alert Admin About Post
Where am I? Original Top of thread | |
: Re: Re: surface finish in RMS (Ra)
: Re: Re: surface finish in RMS (Ra) -- 993334236 Post Reply Top of thread Engineering Forum
Posted by: sowen

02/27/2009, 19:08:44

Author Profile
eMail author
Edit

How did you determine the comparison between RMS and Ra value is 11%?







Post Reply
Tell a Friend (must be logged in)
Alert Admin About Post
Where am I? Original Top of thread |   |
: Re: Re: surface finish in RMS (Ra)
: Re: Re: surface finish in RMS (Ra) -- 993334236 Post Reply Top of thread Engineering Forum
Posted by: Nu2thiS

05/11/2008, 18:14:54

Author Profile
eMail author
Edit

Is rms in in and Ra in m? If so what would a 63Ra finish be in rms? Our profilometer only measures in Ra, Rc, and Rz but the specs call out a 63rms finish or better.

Please help. Thanks.








Post Reply
Tell a Friend (must be logged in)
Alert Admin About Post
Where am I? Original Top of thread | |
: : Re: Re: surface finish in RMS (Ra)
: : Re: Re: surface finish in RMS (Ra) -- Nu2thiS Post Reply Top of thread Engineering Forum
Posted by: Kelly Bramble

05/11/2008, 19:59:14

Author Profile
eMail author
Edit

Ra is typically given in micro-inches. It means Roughness average. Allmost the same as RMS. See you Machinery's handbook. The ISO folks use CLA or Center Line Average. CLA and Ra are interpreted identical.

Ra, RMA, and CLA can be given in inches or MM.








Post Reply
Tell a Friend (must be logged in)
Alert Admin About Post
Where am I? Original Top of thread |   |


© Copyright 2000 - 2015, by Engineers Edge, LLC All rights reserved.  Disclaimer