Shiny finish on stainless bolts/screws -- Vibratory/tumble finishing?

A. There are a couple of things you can do to improve your products appearance. Probably the fastest and cheapest way is to add a liquid polishing rouge to your dry organic materials. A common general purpose rouge is Alum oxide (white in color), but the stainless steel might look better using chromium oxide (green in color). Equipment might also have something to do with your finish also.

A. Dear Sir:

Electropolishing is the best method of improving the appearance and performance of stainless steel screws and bolts.

A. Hi. Most of the plating textbooks have some coverage of electropolishing. In my estimation, the Electroplating Engineering Handbook covers it the best.

But as we move away from generalities and towards the detailed design of a plant and process, you may wish to contact Mr. Bayha in private. Thanks!

Regards,

A. I have had a number of people requesting me to polish hardware and or provide them with a process and equipment. My success is close to 50-50. The reason is time. Vibratory will work provided you endure long time cycles if you go with a treated dry organic mix. Time cycles take 24 to 96 hours, depending upon your concept of what bright polish is. This can be speeded up with centrifugal systems, but in all cases, I have a number of customers who say, and I agree with them, that these finishes are still no match for a buffed part. My answer to them is vibratory systems are not labor intensive and you can still do a quick buff after the process. Also you say you do not need to use abrasives, but most hardware finishes from the manufacturer are over 30 RMS. You can save a lot more time by including a wet abrasive cut down step before the dry process.

A. I would suggest you look into buffing systems. We do buffing of small parts like you describe and have had great success. A rotary dial type would allow you to finish just the head of your bolt and not waste time and media Vibro-ing the whole part. Typical cycle times are around a second per part and there are lots of used systems around.

A. Shawn,
If this is a one-off thing, I don't know that you are going to want to invest in the equipment for this. You may be better off finding a local finishing job shop that has tumble polishing and/or vibratory polishing capabilities.

Beyond that, you can probably find a used polishing machine that fits your budget (they come in all sizes) and I'm sure a salesman for a polishing media manufacturer would be happy to advise you on what type to use.

A. As a former Cardinal student, I would suggest sending the parts to a local shop for tumble polish or electropolish. I can provide you with some contacts that will get you taken care of.

? I have a question for you. Does the surface Ra or RMS matter or is it just for looks. Burnishing media will brighten any surface features.

A. Most fastening hardware is done in mass finishing equipment. Size and type of media depends on the part. Older technology is barrel tumbled in either burnishing media or dry organic media.

A. I take it your parts are basically 2 dimensional and/or flat. You can not get a uniform finish on flat parts in a wet process. You need to use dry organic media treated with polishing compound. If you need some surface modification, you can use pumice in with dry media. If you want to TRY to do a wet operation, do not use a large abrasive media. Maybe stay with steel media. Also remember, there are now dry media shapes available. They look like plastic media, but are used dry.

A. It is possible to get a mirror finish on just about any material. The question is at what cost and expense. For your parts the quickest and least expensive method would be deburring via mass finishing equipment.

A. Not to be rude, but what is your question? You can basically call any manufacturer of mass finishing equipment and give them your specifications and they hopefully can come up with something that will do the job within your budget. Too many unknowns in your question.

A. I think Balakrishnan wants a suggestion on general directions to pursue like vibratory finishing vs. drag finishing, tumbling, magnetic abrasive finishing, electropolishing, etc. But we probably need to know the size of the screws, production rate, and desired finish before much progress can be made.

Regards,

A. In regards to steel screws, There are a couple of ways to go with mechanical processes. Not familiar with chemicals you mentioned, but my experience is that you can darken metal with acids; therefore, I suggest a mass finishing operation. Process depends on time, media, and machines which also depends on part size and quantities.

A. In regards to screw polishing, what comes to my mind is after forging use Vibratory Finishing to descale, which will remove the blackness followed by a good polishing compound .
Once the polishing is done you can do threading so you get a shiny surface.

A. Hi Asheesh. If you can send good photos of what the recess looks like as received and what you need it to look like, suggestions may be possible, although my first thought is that the punching rather than some silver bullet chemical cleaning may be at the heart of the problem. If you truly are referring only to cleaning and brightening, that's one thing; but if you mean some sort of deburring or 'finish machining' please be aware that what can be done with chemicals is usually quite limited.

Both you and we probably need to be careful in trying to transfer to their competitor a knowledge that one of your vendors currently has :-)
If ever you visit that more capable supplier, or require them to transmit any process knowledge to you, you could find yourself on very shaky legal ground regarding theft of trade secrets; it might be better to find another supplier who already knows how to do it rather than trying to teach supplier #2 how to do what supplier #1 already knows how to do :-)

Good luck, & Regards,

A. HI, ASHISH FROM ALIGARH.
TO CLEAN & POLISH STAINLESS STEEL SCREWS AND FASTENER, IT IS A THREE STEP PROCESS:
1. DEGREASING
2.PASSIVATION AND
3. POLISHING OR SHINING.

IT IS CARRIED OUT IN A BARREL, VERTICAL OR HORIZONTAL.THERE ARE PRODUCTS AVAILABLE IN MARKET.

A. Hi Anbukumar. You probably recognize that "most economic" and "best finish" are usually opposites, such that when you are trying to find the most economic you probably must abandon both electropolishing and one-a-a-time polishing methods and settle for bulk finishing/mass finishing processes like tumbling barrels or vibratory finishing. And the question is, will your customers accept this or still challenge you?

Can you get from them any standard you must meet? Surface finish, reflectivity, etc.? What I would suggest you do is sit down with them with sample parts, and establish the degree of polish and shine you need before trying to decide on electropolishing, hand polishing, or the bulk methods discussed on this page. Good luck!

Regards,

A. Not sure of the size or mat'l and finish you are looking for; however, you can use a wet burnishing process (either steel or porcelain) in a vibratory system. If you have a lot of detail, you might want to look at dry burnishing using a porcelain organic mix.

A. Hi cousin Sukesh. This thread has been about exactly that for 21 years now :-)

Vibratory mass finishing, tumbling, and electropolishing have been suggested & discussed. As a fastener manufacturer you've surely made some attempts and enjoyed successes & failures? Please expound on them and engage some of the dozens of previous postings -- because starting a thread over with an abstract general question usually proves to be the kiss of death to any discussion :-)

Thanks & Regards,

A. Hi Justen.
If you are asking whether it can be done in sequential steps with different media in the different steps, certainly! Read on.
If you are asking whether you can do it rapidly in a single step by mixing media of the proper sizes together in the proper proportions, sorry, no.

You need very fine media at the end of a mirror polishing process because any rough or medium media will re-scratch it. But trying to do the rough polish with very fine media, like digging the foundation for a skyscraper with teaspoons, will take a very long time. As Tony mentions below, if you're willing to let vibratory steps take several days you can use finer media for them.

Judging from the dimensions you offered, it sounds like you want to polish it before welding on the threaded rods, and possibly before welding on the C-shaped hoop. Although I'm not in possession of all the facts, it seems to me that it should be vibratory finished after the C-hoop is welded on. I would think that vibratory finishing could do a nice job, but you could add a quick manual buffing of the most visible and exposed surfaces in just minutes.
Luck & Regards,


Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey