What exactly is a "rough" surface?
What exactly is a "rough" surface?
(OP)
I am trying to find the definition of a "rough" surface in terms of numbers, equations or something that can help me distinguish between a "rough" surface and a "smooth" surface.
You might ask why this is important? There are some "rough" surface mathematical models I have seen from Williams and Kapoor, I can't not seem to find what is classed as a "rough" surface and what is not?
Can anyone provide any input? Thanks.
You might ask why this is important? There are some "rough" surface mathematical models I have seen from Williams and Kapoor, I can't not seem to find what is classed as a "rough" surface and what is not?
Can anyone provide any input? Thanks.





RE: What exactly is a "rough" surface?
Different machining processes can produce varying surface finishes with different roughnesses. There is no point (to my knowledge) that a surface becomes "rough" or a surface becomes "smooth", but a constant gradient of more and less rough/smooth.
Perhaps a better description of what you are trying to achieve could help me clarify more if needed. :)
RE: What exactly is a "rough" surface?
Rough or smooth depends on the intended use of the surface.
How to measure roughness : profilometer (contact, contactless),comparison (existing samples)
Profilometer can provides at least 30 parameters to measure the roughness of a surface:
Ra,Rt,Rz,Rv,Ry,Rp,Rq...etc
Selection of the right parameter depends on the intended use.
Most known factor is Ra and Rz.
You have an ANSI standard with complete definitions and equations
Thanks
RE: What exactly is a "rough" surface?
http://www-mech.eng.cam.ac.uk/Tribology/research/1...
RE: What exactly is a "rough" surface?
Surface finish requirements are absolutely relative to your application. I suggest you order a surface finish comparator. This will connect the numbers in your handbooks to actual surface finishes.
Who are Williams and Kapoor? I can find a fluid mechanics book by Baljeet S Kapoor. My college book, Fluid Mechanics With Engineering Applications, by Daugherty and Franzini, has a table on page 213 showing absolute roughness in feet and millimetres. Maybe you need a better textbook.
--
JHG
RE: What exactly is a "rough" surface?
Not sure if that is useful to you, it is not the academic approach.
RE: What exactly is a "rough" surface?
RE: What exactly is a "rough" surface?
Once you know these things you can determine the material finish processes required and the roughness value to assign to it.
Also keep in mind that electropolishing is a popular process that puts a fairly good luster on the surface. While I believe electropolishing is useful and economical, I've seen situations where a 125Ra surface has been electropolished and while it looks smooth, it's really just a shiny version of the same rough surface. So don't let looks deceive you.
RE: What exactly is a "rough" surface?
- Steve
RE: What exactly is a "rough" surface?
...but you can always roll it in glitter.
www.tynevalleyplastics.co.uk
It's ok to soar like an eagle, but weasels don't get sucked into jet engines.
RE: What exactly is a "rough" surface?
- Steve
RE: What exactly is a "rough" surface?
surface finish is as explained from the previous post, is determined from the application, function of the part.
eg: seal surface, bearing surface, gear surface.
most drawing's I have seen specify Ra micro finish. which depending on the type of part & size, will determine the method of inspection.
for my application, small fine pitch gears, most surface finish are measured with a profilometer. as noted by others.
test blocks can be used to calibrate & test the profilometer.
I would like to add that micro finish specified can & will dictate the manufacturing method.
if the surface finish specified is an 4 micro or better, the the supplier will have to use the right tools to obtain it.
use tight surface finish only, and only when it is required, or the cost of the parts will increase.
Normally a 63-125 is adequate for most applications. and I would consider a smooth finish.
in my world of machined, case harden gears, & shafts, a 250 micro finish is a rough surface. 125 or 63 micro finish is normally standard.
for my type of work. however the same parts can & do mix in different micro finish call outs.
gear profile can be between 4-32 micro, journals can be 4-32 micro surface finish, non functioning areas can be 32-125 micro.
some surfaces can be 2-4 light bands, for flatness & micro combined.
I have given example of different specified surface finishes.
HTH
Mfgenggear
if it can be built it can be calculated.
if it can be calculated it can be built.
RE: What exactly is a "rough" surface?
JordanL, Zinov, thanks for your explanations and information. Zinov, I am Williams and Kapoor is my best friend... no just kidding :)
Tmoose, yes part of my interests in this is with regards to shakedown.
SomptingGuy, sorry I didn't understand your post
Everyone else, thanks again!!