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Up Topic Welding Industry / Technical Discussions / Need some help with a surface profile for polished SS
- - By jwright650 (*****) Date 03-18-2009 15:09
I was wondering if this is a typo or actually a valid finish requirement. Not being familiar with this, I thought I might ask the forum and see what you guys can tell me about it.

"The initial condition of the steel to be exposed in use shall conform to polished finish No.4 with RMS surface roughness equivalents(Ra) of 0.5 microns or 20 micro inches."
Parent - - By Kix (****) Date 03-18-2009 15:39
I know they require different surface roughness equivalents for stainless sinks and counter tops that will be used in the food industry for bacteria trapping reasons.  Are you asking if a No. 4   .5 micron or 20 micro inches is a bit excessive?
Parent - - By jwright650 (*****) Date 03-18-2009 15:45
I was wondering about the .5 microns......was thinking it should be 500......LOL

This was in a misc. package and is being sub'd out, which I'm glad because my surface camparator that have shows that 20 microinches is fairly smooth(my comparator has 32 then skips to 16), but I can tell it is slicker than we want to fool with in-house.
Parent - - By TimGary (****) Date 03-18-2009 17:33
John,

When working in a pharmaceutical equip manufacturing plant, we had to produce product contacting surfaces with 20 or 10 ra surface roughness specs as per ASME BPE.
This surface condition is incapable of trapping anything as small as bacteria.
I can't imagine why you would have that requirement come through a structural steel shop.
Somebody must have mixed up their specs...

Tim
Parent - - By jwright650 (*****) Date 03-18-2009 18:28
Tim, this is in a spec concerning the entrance canopies of a project....LOL
Parent - By TimGary (****) Date 03-18-2009 19:55
Well John, the only way to get that tight of a surface finish is to first mechanical polish the heck out of it and then send it out to be electropolished as well.
Oh, and don't forget not to touch it after it's been polished, or you'll scratch it.
You should be able to charge a pretty penny for all that.
The erector is screwed though..

LOL

Tim
Parent - - By DaveBoyer (*****) Date 03-19-2009 01:23
     How thick is the material? I am thinking that if  7 ga. or under, cold finished sheet will probably meet that spec. [20 micro inches], if it doesn't have handling damage.
Parent - By jwright650 (*****) Date 03-19-2009 11:46
I have no idea, I was only asked to look into the finish spec to see what the finish was supposed to look like @ 20 microinches. So, I'm not sure what structural shapes we are dealing with here, other than I was told that it was Stainless Steel.(no idea what grade or anything)
Up Topic Welding Industry / Technical Discussions / Need some help with a surface profile for polished SS

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