Letter 28073

Need help surface polishing 304 stainless steel discs  

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Hello,

We are surface polishing 304 Stainless discs, 5.25" dia x .3125" thick. We are doing this using a rotating polishing table spinning at 300-500 rpm. It is done by hand using a small rod inserted into the center of the plate and pushed down against polishing paper. We start with 120 grit and work through 180, 240 and finish with 400 which gives us a close to mirror finish. Our problem is that it is extremely time consuming and not consistant from person to person. Our volume is increasing dramatically and I would like to find a mechanical or automated method of polishing. Any advice on where to find a method or machine would be greatly appreciated.

Al Edwards
Electronics Mfgr. - Worcester, Massachusetts

Besides production, what is the most important factor here, flatness, surface RMS, or mirror finish?

AF Kenton Nova Finishing Systems Inc. Huntingdon Valley, PA

Al, the first question I would ask, is why are you polishing 304 stainless (2B or #4) to a mirror finish if it's already available in a mirror finish? At my company we use a 304 #8 non-directional mirror finish (one side) material that works great for us. It comes with a pvc coat on both sides. I'm not sure what your application is, and why you are polishing 304, but you should look into this material. It may be cheaper and definitely less time-consuming.

Martin Magaña
Manufacturing - Anaheim, CA

AF,
Thanks for your response. A little bit more information may help: After we polish the plates to a 400 grit finish(done mainly to get them flat and smooth), we vapor-hone them to a dull, grey finish. The clean, uniform finish is most important to these plates.

We then use the plates in a manufacturing process and they become scratched or stained which renders them useless. To remove the scratches we have to put them on a surface grinder and take a few thousands off of the surface(this is the only way we have found to remove the vapor-honed finish). Then we polish and vapor-hone again.

The problem is that the plates are easily scratched and hours of work can be quickly wasted by one slip of a production operator. We're really looking for a way to take the scratched plates and quickly re-finish them for production.

Martin,
Thanks for your suggestion. The mirror finished steel would be great for the first use but as soon as it is scratched we would be back to our original problem. I may look into this option anyway to save time up front.

Al Edwards
Electronics Manufacturing - Worcester, Massachusetts

I am still a little confused about your problem. It sounds as if you should be more concerned with protection rather than refinishing. In lieu of protection, maybe you should consider hard coat plating if it is acceptable. Regarding refinishing. I'm sure you are aware of disc lapping equipment. I am unclear if the problem exists on both sides of the part. If it is on both sides, there is double disc systems. I don't think I'd recommend any other mechanical method, considering your concern with flatness.

AF Kenton Nova Finishing Systems Inc. Huntingdon Valley, PA

I polish tanks & wheels on trucks also do some car resto work. With stainless trim I use wheels on an old wood lathe different compouds my final substance is to use dry powder cement . It brings up the shine an amazing amount.

Hope this tip helps

Bob Shields
- Sound Beach, NY

Dear sir ;
We are a manufacturer of disposable needles; in our process of nannula manufacturing we need mirror polish with dull shine;
kindly suggest the detail for this process;
Thanx with regard;

Rajesh kumar
healthcare devices - Rewari, Haryana, India

Hi, Rajesh. The list of things you might be doing wrong is short compared to the whole universe of things you must do right :-)

If you describe what you are doing and the problems it is leading to, you are quite likely to get good suggestions from the readers. Whereas if you ask them to start at scratch and describe everything you could or must do to establish a capable manufacturing process for polishing needles, they are not going to reply except perhaps to recommend books on the subject. Good luck, and please get back to us.

Regards,

Ted Mooney, P.E.  finishing.com Brick, New Jersey

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