Questions about polishing stainless steel

[badav]

hello. i am attempting to polish some stainless steel moulds. i am using a 2850rpm bench grinder, 6" sisal & loose cotton wheels with black & green compounds.

i have been reading this site extensively but i have some questions too. i notice in the "pick a buff" link on the main page, this information is listed to polish stainless.

1st Stage - Rough Cut To Remove Scratches
Use Sisal Wheel With Emery (Black) Compound
2nd Stage - Final Cut and Initial Polish
Use Spiral Sewn Wheel With Stainless Steel (Green) Compound
3rd Stage - Final Polish (or Luster)
Use Spiral Sewn Wheel With Stainless Steel (Green) Compound

what do you do different in the 2nd stage, as opposed to the 3rd stage. is it just the direction that you apply the workpiece against the wheel (cut/colour motion??

so far the way i have done it is to hit the piece with 400,800 & 1200, then buff with sisal/black and polish with loose cotton/green. what could i be doing to improve my results.

[mpierich]

Hi,

You don't say what results you are getting now, so it's tough to say how to improve it.

Setting aside the "pick a buff" thing (I don't understand it either).....I don't think it's necessary to go past 400 or maybe 600 grit with the sanding. Your molds must be very smooth already if you can start with 400. And, going from 1200 to black/sisal is probably a step backwards, in my experience.

If an item is rough-cast, I start with 120 or 220, then 320, maybe 400; then sisal/black, spiral/black, then loose/green or loose/white depending on what works best for that particular alloy.

If you're going to do a lot of these you might want to get a buffing machine...your grinder is probably a little underpowered.

[Rasper]

I find that worn out 400 grit is as far as I really need to go on stainless. After that I go directly to the green if I'm polishing large areas, or to black if it's small pieces of hardware. I can't seem to get the black to cut very well on large flat areas. The stainless seems to break down the emery, or something.
First I bear down hard and get the metal hot enough to melt the compound. That's when it really starts cutting. That cuts out all of the 400 scratches but leaves some of it's own. Then I go back over it lightly with the same green and that usually produces a fine polish.

The main problem with stainless is the sanding. It's so damn hard. It's almost impossible to make yourself sand it enough with one grit before moving up to a finer paper. It's a lot easier to sand those scratches out than to polish them out later. I have a good bit of experience polishing stainless and I still make that mistake frequently. I use a 2500 rpm air sander with hook-it discs kept wet with WD-40. It makes a mess throwing the WD-40 all over the place but it cuts fast and the paper lasts a lot longer than if used dry.

Richard

[jrow]

Originally Posted by badav

hello. i am attempting to polish some stainless steel moulds. i am using a 2850rpm bench grinder, 6" sisal & loose cotton wheels with black & green compounds.

i have been reading this site extensively but i have some questions too. i notice in the "pick a buff" link on the main page, this information is listed to polish stainless.



what do you do different in the 2nd stage, as opposed to the 3rd stage. is it just the direction that you apply the workpiece against the wheel (cut/colour motion??

so far the way i have done it is to hit the piece with 400,800 & 1200, then buff with sisal/black and polish with loose cotton/green. what could i be doing to improve my results.

First off what is the condition of your molds prior to your starting to sand? If there are no significant scratches I would go direct to the Emory on a sisal buff, then to green on a sewn buff.
I believe Stage 2 and Stage 3 refer to cutting (initial polish) and coloring (polishing and luster) in that order. Remember to rake your buffs often.

John

[badav]

The moulds are in very good condition with no dents or major marks, but they are over 30 years old so there are lots of scratches mostly fine that make the mould appear cloudy.

the results that i am getting are ok. the problems im having are probably due to inadequte sanding, ie: not removing all scratches left by a lower grit paper

these are a couple of pics i took that appear ok at first, but you can best see the scratches still left on the piece under the flash of the camera.

if anyone can give me any tips to improve the finish im all ears as im just a begginer

[jrow]

badav,

If you can catch the scratches with your fingernail then use some 220 or 320 greaseless and then go to Emory on a sisal buff.
You can get the greaseless at Caswell's.
John

[garymcgowan]

"....what do you do different in the 2nd stage, as opposed to the 3rd stage. is it just the direction that you apply the workpiece against the wheel (cut/colour motion??


I think that is a mis-print. In stage 3 it should be done with a loose cotton wheel with green compound. In the second stage, first do a cut motion and then do a color motion.

Hope this helps.

Gary

[badav]

Originally Posted by garymcgowan

"....what do you do different in the 2nd stage, as opposed to the 3rd stage. is it just the direction that you apply the workpiece against the wheel (cut/colour motion??


I think that is a mis-print. In stage 3 it should be done with a loose cotton wheel with green compound. In the second stage, first do a cut motion and then do a color motion.

Hope this helps.

Gary

Cool, i have been getting good results using that following combo

sisal/grey
spiral sewn/green
loose/green

-cheers

[Brocca]

To speed things up a bit in my shop we would sand by hand first 4 stages of papers (or stones) up to 400 this get all the scratches same size and depth once you get this your on your way, then sisal/green(or gray) spiral/green loose/yellow, green cuts the best and speeds things up from what I found, otherwise you spend more time on the wheels, you should use a heavier touch on sisal to very light on loose.......should be mirror like. But to be honest you should be able to stop at the green/spiral compound, for a mould that is all you need. Just my 2 cents worth.