polishing stainless to mirror finish or close enough without scratches

[brendan h]

got some 304 stainless i want to polish up to get a nice shiny finish. i went out and got a polishing kit from a hard ware store. it came with 2 blocks of compounds (white and grey) and 2 wheels, cotton (lose leaf i think?) and a straw wirery type thingo. sorry i dont know the names.

what is the correct way to polish? i ground the stainless back using a 120grit flap disk, then used the grey compound with the straw wheel then i used cotton with white compound. while its the finsh i want it still got a **** load of scratches. what have i done wrong? do you have to clean the compund off before using a new wheel and compund? what do i use ect.

and is there a way to clean the wheels?

i am also using a drill aprox 2500-3000rpm. (tag has rubed off)

the wheels are rated to 3000rpm

 

[stormin]

I'm not an expert but I think you want to use a lot finer grit than 120 before going with the polishing compounds.
Try working up through 400 grit, 800 grit before thinking about polishing.

 

[brendan h]

i have yet to see any flap disk thats 120+

 

[gordon stephenson]

Stormin is quite correct, you will have to remove the scratches before polishing, get some much finer abrasives than 120,

 

[brendan h]

as i said, i am yet to see a flap disk thats 120+

the part is small and i could probably use some fine wet and dry but realy what if the part is too big to sand by hand?

 

[stormin]

Get a DA sander with adhesive or hook backed pads and you can get any grade you like.

 

[brendan h]

never though of that thanks

 

[irondarren]

We just made some stainless brackets, from 150 x 10mm flat. The bar wasn't the best quality, rough finish. That was worked up with DA disks 80 grit, 120 grit, 180 grit, 240grit, 320 grit, 400 grit, 600 grit. The finish was a dull polish, you could see micro scratches in the stainless from the 600 grit, had it of been worked even more 800 grit, 1200 grit and then G3 rubbing compound it would have no doubt come out as a mirror finish.
Check the forum shop, there are polishing disk available similar to the flap wheels except with scotch brite type material instead of abrasive paper

 

[brendan h]

i have a sander that vibrates back and forwards. you basicly cut your own sheet to fit it. this should work shouldnt it? if not i do have an orbital sander just havent got any disks

 

[irondarren]

brendan i forgot to mention we used the scotch brite sheets, our DA is the hook type one so the scotch brite kind of sticks to it. scotch brite is that green abrasive material that is often part of a washing up sponge.

 

[brightspark]

white and grey compounds ok. green is for stainless but as everyone says all the scratches MUST be removed before polishing. ebow grease needed

 

[scott0031]

ok right then! An effort at a polishing guide!... sort of

Firstly, you can polish out pretty much anything other than deep gouges that will only get exaggerated when polished. Half your problem is the equip you are using and the materials you are using to do the job, there is a combination of two main things going wrong here.


The first thing to deal with here is the polishing compounds and the mops. The straw mop as you call it are 'sisal' mops meant for roughing out with a fast cutting compound like the grey one you have, its most likely to be something similar to 'steelcut' which can be used on steels, stainless and aluminums for roughing purposes. It's actually meant for steel only but in fact works much better than some of the soaps for certain applications.

The finishing mop for what you want is wrong. You need stitched white cotton mop. The one you have is not stitched and is not suitable for that sort of work other than very very very high finishing normally associated with jewelry applications. It is a bit hard to define exactly what the white soap is that you have as there are many different makers and different names since the invention of all these polishing suppliers............ but its all the same stuff often only originating from one or two sources. They do generally use similar colours with the soaps to define the grade so the white is correct for finishing but the mop is no good. White stitched is what you need. This comes down to heat generation and the pressure you can apply to the mop
(see below for more details)


The process and equip you are using will make life very difficult indeed.The main thing people miss with metal polishing is 'heat'. Heat generation is vital to polishing. This is something that is hard to achieve with hand held equip. Now your wondering why? Well the reason is simple. The soaps are a wax with cutting compound suspended in it. If you cant generate enough heat to melt the wax you wont release the cutting compound its that's simple! All you end up doing with the mop is pushing the wax around the job without melting it. That's why people have a hard time with all these diy kits as the sellers of such kits don't tell you about whats actually needed to polish successfully. They in the main are only interested in selling there products to make money.

This moves onto the next stage with the equip you are using to polish with. To generate enough heat you need about 2800rpm You need the torque in the equip to withstand a fair amount of pressure applied to it to get that heat generation. Unlike most engineering applications where heat is the enemy, polishing is one where heat is your friend. If you cant apply enough pressure the generate the heat you wont melt the soap. Hence the problematic cycle starts all over again. It is hard to generate enough heat with hand held equip by its nature . Its not very controllable verses a static polishing machine. It is much better to have the equip static and move the job about the wheel, that way you can apply pressure in a controlled manner with constant pressure compared to hand help equip that wants to spin all over the place. Its hard to control by comparison and very hard to get the heat generation. The heat generation is not lukewarm, its not hot, its bloody hot! So hot it will blister your skin in a second if touched with the bare hand. So several layers or gloves are often used, that's so you can withstand the heat in the job.


It is true its a good idea to take out larger scratches by hand (also as mention a DA is good for flatter surfaces) but it does depend on the job and the shape of it. Lets take a motorcycle engine casing v a flat sheet. An engine casing is full or radius-es and odd shapes and as such refracts light at different angles, this being true means deeper marks simply polished out are not as noticeable to the naked eye when fully polished. A flat sheet on the other hand is a different matter it does not refract light in the same way as its flat and wont be as directional as a engine casing. So that in essence needs a more uniform approach to the polishing process. The polishing should be done for rouging multi directional and for the first finishing process with white stitched mop then uni directional for final finishing. Polishing is still generating a series of scratches. All you are doing is making those scratches small and smaller. The smaller they are the more they will reflect light. That's why if you use a a multi directional format for finishing it wont look to hot. What you have done is created scratches going in all directions and it will reflect that light in odd directions, so it will look dull in places.
Something that is flat is uniform by its nature so the polishing should follow suit. The proof in the pudding with this is, guys that have used mill polished stainless sheet. There ya go!

After roughing with a sisal mop and roughing soap, you should have a dull but totally uniform finish with no visible scratches to the naked eye. When you achieve that, then its time for finishing. Its a bit like painting a car if whats underneath is bad the end product will be bad. If its prepared well the end result will be good.

To clean the mop all you do use a wire brush, an old saw blade, Lump of steel with a square edge Anything will do. Be careful the mops can bite hard if you don't take care. Treat polishing wheels with respect when carrying out this process

The polishing process can indeed be time consuming, But it shouldn't be as time consuming as people think with all these diy kits. These kits make hard work out of a pretty basic task for the many that purchase them. You wont get the same finish as you will from a polishing machine. All due to the facts as mentioned above. You can get good results with a lot of patience and time. The comparison is do you want to spend hour upon hour trying to achieve something that's only half good or send it to someone for 20 quid and get job done to a much higher standard and really at a lot less cost in the long run.

Again to see the results you can get please look at the motorcycle section of my pic gallery's. I cant take pics that well but it will give you the general idea. Ya can pick your pimples in that sort of finish if ya want!


Hope this info is of some use and i promise you gained by hard earned experience and hours upon hours being covered in muck from metal polishing!

Please excuse any typos cant be assed to re-read it anymore


Kind regards,



Scott (ward eng)

 

[cheech]

totally agree with Scott, heat is the key, i converted my bench grinder to carry the mops, ok if your "piece" is small enough to handle.
Use Vienna Lime (white powder) to clean the metal between compounds, with a soft cloth! to avoid cross contamination.... can be a pain..... and yes it can be a loooooong process that can only be appreciated by yourself at the end.
Hours and hours of work bloodshot eyes, black face, finger tips burnt and sore and the wife says "oooh thats shiney, what else you been doing!" Aaaaaaarrghh

 

[brendan h]

well i got to to a mirror finsh that i like. while i think it can be better it good enough.

i was using a stiched rag btw.

can i use the same mops on stainless and aluminium ect or 1 for 1 metal.

also do you need to clean the compound off when swaping mops and compunds?

thanks for your info i now know a bit more thanks

 

[scott0031]

well i got to to a mirror finsh that i like. while i think it can be better it good enough.

i was using a stiched rag btw.

can i use the same mops on stainless and aluminium ect or 1 for 1 metal.

also do you need to clean the compound off when swaping mops and compunds?

thanks for your info i now know a bit more thanks

Ok the mop you described sounds like an non stitched type.

You can use the mops on what material you like, but remember the sisal ones are for roughing out. There are different mop types running into dozens of them for certain jobs, materials and applications, but this is not something you need to concerned with for home type use.


It wont do any harm to clean the mops, you really should not be swapping the soaps between mop types. It's not that it shouldn't be done its a case of why? Sisal mops (roughing mop) with roughing soap grey in this case. White stitched mop (finishing mop) with finishing soap white in this case. You should not be using roughing mop with a finishing soap , it serves no purpose and visa verse.

Those two soaps you have will do all ferrous metals, in this case those being steel and stainless. They are also used on aluminium. So you really have no need to use different soaps. There are higher finishing soaps out there but they are really not needed one bit. suppliers will tell you different but i have these soaps and never use them, they are just not needed in my view. Those two soaps and mop types will bring those materials up to a very high standard indeed. All the polishing work in my pics uses the exact same mops and soaps you are using. If you saw those items in the flesh they are totally flawless and finished to the standard of high class jewelery. So it speaks for itself.

If you want to use a totally different finishing soap for some reason on a finishing mop it wont do any harm to clean off the mop as i described above, its not totally essential as the mops are a constantly wearing item as such they do renew the mop surface with use. Materials like ally can make the mops a bit loaded with the material being polished. You will soon know as you will see it on the mop/feel it and see the job surface finish deteriorate. The mop will have glazed type deposits on the surface of the material being polished, this does tend to happen more with the white stitched finishing mop than a sisal mop as the sisal is very coarse and lets go of the sisal fairly easily.


Kind regards,


Scott

 

[Welding Wannabe]

hey thanks scott for the quick lesson is diy polishing, maybe I'll wipe the dust off the polishing kit i bouight a couple of years back that attaches to my bench grinder and actually try and use it

 

[Arsonista]

That was interesting reading Scott. Thanks for taking the time.

 

[manicman]

hi there,
I'm just getting started in polishing stainless and it would be a great help if someone could explain which mop would be best suited to which soap for me to go from starting polishing to the final - hopefully mirror finish :-/
also, are there any specialist polishing websites out there peep would recommend to a newbie polisher,
Thanks

 

[brightspark]

hi there,
I'm just getting started in polishing stainless and it would be a great help if someone could explain which mop would be best suited to which soap for me to go from starting polishing to the final - hopefully mirror finish :-/
also, are there any specialist polishing websites out there peep would recommend to a newbie polisher,
Thanks

hi read the previous posts and all the answers are there

 

[armalites]

This site is worth a look

http://www.thepolishingshop.co.uk/acatalog/Polishing_Mops.html

Gives a good description of everything including the compounds and what they are used for.