Sand blasting standards: Swedish SA 1, SA 2, SA 2.5, SA 3 vs. NACE and Ra

A. Are you sure you are talking Ra? I don't think you can achieve those results using any blasting media.

Q. For example: machined surface roughness Ra 12, can we blast it to SA 2.1/2 and achieve surface roughness 6.3 Ra?

A. Hi, Abdulah. I think AF (Tony) told you "no". To the best of my knowledge, blasting is for cleaning (removing surface contaminants), and I have personally never heard of anyone attempting to polish an article by blasting, so I think he's right.

Regards,

A. Dear Mr. Ashok Kumar, Sa 2.5 is a surface cleanliness level. So how can know grit size?
Regards
Sohail Hashmi

Patron: "Waiter, my strawberries & cream have mud in them! Did you wash them?"

Waiter: "No problem sir, we can re-slice the berries smaller if the chunks are too large for your taste".

A. Hi cousin Sunilantonyt --

Please start at the top of this page and read it slowly and patiently to understand that Sa 2.5 is a visual standard for cleanliness, like the patron is talking about. It is not a measurement of surface profile like the waiter is talking about -- and no conversion between the two is possible. Good luck.

Regards,

A. Hi Arijit. Please carefully read the page. I already answered that question on October 21, 2012: "HMG Paints Ltd. offers a free 24-page PDF with pictures of these surfaces at: https://www.hmgpaint.com/knowledge-base/pdf/KNB0026.pdf". Good luck.

Regards,

A. Hi Boby. Perhaps we continue to misunderstand each other's words and phrases, but many people have tried to make it clear that Sa 2.5 is a visual standard for cleanliness and it has nothing to do with surface profiles, which are measures of roughness not cleanliness.

Regards,

A. Hi Thiruppathi. I'm not an expert in this subject, but I can't imagine how it could be a problem. It sounds to me like you've simply removed any doubt that the surface is clean enough to comply with Sa2.5. Good luck.

Regards,

A. Hi Shriram. This is available for Rs 130 from Jain Book Agency at www.jainbookagency.com/newdetails.aspx?id=110891

Good luck.

Regards,

A. Hi Birendra. Some have said Sa stands for "standard abrasive", others say it stands for "sand", and others claim the "S" stands for Swedish; I say you can't translate abbreviations between languages in the first place :-)

But perhaps the interviewer's problem with your answer is that "degree of cleanliness" may not have quite conveyed the nature of ISO-8501-1 and the ratings like Sa 1, Sa 2, Sa 2.5 and Sa 3 that are associated with it. I think the main point, which is made several times in this thread, is that it is a standard which includes 24 photographs and is a guide for "Visual assessment of surface cleanliness". Please download the short free booklet from HMG Paints that was previously mentioned and I think you will understand it thoroughly. Good luck.

Regards,

A. SA:Sweden Airblast
ST:Sweden Tool

A. Hi cousin Rohan. Please study this thread and you will learn that your question isn't quite properly formed -- because SA-2.5 has nothing to do with microns or surface roughness. Good luck.

Regards,

Hi cousin Adik. Thanks for your patience in reading the whole thing.

Unfortunately I do not have all of the standards that people mention on this site, but ISO 8503-1, which you are talking about, is not the ISO 8501 that other people were talking about. ISO 8501-1 is the "visual standards for cleanliness", and this cannot be equated to surface roughness because it is a visual standard for cleanliness and not a roughness standard. We gave an analogous example that strawberries can be clean or dirty irrespective of the size of the slices.

ISO 8503 appears to be "surface roughness" standards, not visual cleanliness standards.

I don't believe that anyone said that surface roughness "cannot be the outcome of a blasting process and it isn't measurable". The whole point of ISO 8503-1 seems to be that it can be the outcome of blasting and it is measurable. Anthony Kenton and myself did express the opinion that it was probably not practical to achieve an Ra 6.3 polish by blasting, but I think I may have been too hasty :-(
I, and probably Mr. Kenton, was thinking in microinches instead of microns, but upon re-examination microns was probably intended and Ra 6.3 microns is probably doable by blasting -- which is not to say that Abdullah Ansari will necessarily be able to achieve what he wants; I don't know :-)

Regards,

 Hi Yogesh. I hope some reader fully understands the context of your question because it is too abstract for me. If you are a local weld shop offering to clean up a customer's old lawn mower, the answer is no. If a specification you are processing to requires it, the answer is of course yes. If you are an aerospace shop involved in processing airliner components, the answer is possibly yes.

Regards,

A. To add to Ted's answer. We also need to know what materials you are working with. You should also be aware that oxidation is always a problem which is caused by temperature and humidity.