How to make stained mill table or lathe ways look like new... 4000 grit ?

Milacron · Oct 23, 2014

Wish I had before and after photos but had a Fanuc Robodrill where the table had no dings, no rust...unless the stain spots were actually rust...anyway it looked like crap compared to new due to ugly stains.

Took a fine 2" Roloc type abrasive disk on die grinder to the spots and went thru 800, 2000, and finally 4000 grit emory paper on the entire table and was surprised how nice the end result is....looks very close to freshly ground...can see reflections in it. The catch is you go thru alot of sandpaper as the finer grades get clogged almost immediately.

Wonder if any of you have done similar but gone about it differently..perhaps with abrasive compounds and rotary buffer ? Anyone taken something like this (i.e. mill table size) and gone even further still...such that it looks absolutely as nice as the nicest ground surface....i.e. almost a mirror...and if so, how did you do it ?

sable · Oct 23, 2014

Probably not quite what you are asking but I think Retired UK did a pretty good job in this thread .

http://www.practicalmachinist.com/v...erman-lorch-schmidt-lathe-restoration-282932/

He answered my question about cleaning up the unpainted surfaces in post #9

kustomizingkid · Oct 23, 2014

I wonder how a stainless graining tool would do.

Graining and Buffing (D) | Waters Industrial - Stainless Steel Finishing

Milacron · Oct 23, 2014

sable said:
Probably not quite what you are asking but I think Retired UK did a pretty good job in this thread .

http://www.practicalmachinist.com/v...erman-lorch-schmidt-lathe-restoration-282932/

He answered my question about cleaning up the unpainted surfaces in post #9

Re Brasso, I find that a little too abrasive for a mirror finish. Nevr-Dull better....but either 4000 grit or finer compound necessary to go along with the Nevr-Dull as it has no abrasive of its own I think.

jrmach · Oct 23, 2014

"800, 2000, and finally 4000 grit emory paper on the entire table"

You are on purpose removing material from a precision surface ?

Milacron · Oct 23, 2014

jrmach said:
"800, 2000, and finally 4000 grit emory paper on the entire table"

You are on purpose removing material from a precision surface ?

I suppose so but most folks (of which I am not one) don't seem to be bothered by removing much larger amounts of material to get below the pitting of truely rusted surfaces like lathe ways that have been out in the rain. Even steel wool, which seems innocent enough, has to be removing some minute amounts of "precision surface" to shine up a rusted area. In the case of the Robodrill table I do wonder exactly how much material was removed overall...suspect it less than .0003" but don't know really.

An interesting experiment would be to take a small section of ground iron that one could more easily measure the thickness of, stain it in spots, get it back to original luster via 4000 grit and then take new measurements.

swarf_rat · Oct 23, 2014

Milacron said:
An interesting experiment would be to take a small section of ground iron that one could more easily measure the thickness of, stain it in spots, get it back to original luster via 4000 grit and then take new measurements.

That would take some work, but you could chuck a piece of whatever material in a lathe, measure the diameter, go after it with various grits and easily measure the amount removed. I was using the fine Scotchbrite to shine up some precision surfaces, and wondered how much I was removing so I tried that on a mild steel bar. Removing even 0.0001 takes a long, determined session.

Milacron · Oct 23, 2014

swarf_rat said:
That would take some work, but you could chuck a piece of whatever material in a lathe, measure the diameter, go after it with various grits and easily measure the amount removed. I was using the fine Scotchbrite to shine up some precision surfaces, and wondered how much I was removing so I tried that on a mild steel bar. Removing even 0.0001 takes a long, determined session.

Yeah I've done that before and noticed the same thing....even when the new Scotchbrite cloggs with material the dimensional change in the part is less than .0001"......which is what gives me the impression what I might have removed on the table in question is very little indeed.

magneticanomaly · Oct 23, 2014

I believe a "stain" on a ferrous metal surface is fine pitting. To remove, got to get to bottom of pits. I'd rather leave the pits as oil-holders, than lower the whole surface.

dgfoster · Oct 23, 2014

OP, did you use some form of liquid like water or naphtha to reduce clogging? I have found either one to help get a lot more life from silicon carbide paper and use naphtha on diamond stones for the same reason when sharpening.

Denis

BTW, "after" pics only would be interesting.

Milacron · Oct 23, 2014

magneticanomaly said:
I believe a "stain" on a ferrous metal surface is fine pitting. To remove, got to get to bottom of pits. I'd rather leave the pits as oil-holders, than lower the whole surface.

I think you could be right but after all these years I still don't know for sure...sometimes the stains seem more like color changes that might not involve pitting. But how exactly that might occur, especially in spots, is not clear either. Suppose it could be coolant residue...but why certain spots and not the whole table....thicker drops in some areas that take longer to evaporate perhaps ?

And then there is the classic mill table "outline of the vise" stain, where presumably coolant get's trapped and never completely dries ? Is that darker color (sometimes black) purely due to rust pitting ? I should examine that sort of thing with a microscope sometime...might be interesting what I see.

Milacron · Oct 23, 2014

dgfoster said:
OP, did you use some form of liquid like water or naphtha to reduce clogging? I have found either one to help get a lot more life from silicon carbide paper and use naphtha on diamond stones for the same reason when sharpening.

Typically either WD40 or the residue from Nevr-Dull. Have not tried Naphtha.... should I ?

dgfoster · Oct 23, 2014

Milacron said:
Typically either WD40 or the residue from Nevr-Dull. Have not tried Naphtha.... should I ?

I doubt it would be any better than WD-40 which I think is primarily kerosene. Naphtha would be a little thinner. Could not hurt to try. I keep mine in the Ronsonol plastic dispensers which I find convenient and refill by popping of the the open/close spout assembly. That makes it very handy and I do not have to fool with the gallon container the naphtha (Ronsonol) came in.

Denis

andrewmawson · Oct 23, 2014

Staining is sometimes microbial activity - particularly below vices when coolant is used

jamie76x · Oct 23, 2014

I use scotch bright pads with CLR bathroom cleaner. It removes the rust and most stains without taking hardly any material off the surface. I start off with medium and work my way to fine.

Milacron · Oct 23, 2014

jamie76x said:
I use scotch bright pads with CLR bathroom cleaner. It removes the rust and most stains without taking hardly any material off the surface. I start off with medium and work my way to fine.

Which is fine for some things but not what this topic is about. What I'm talking about are techniques to go beyond the usual "good enough" to achieve a mirror finish.

Milacron · Oct 23, 2014

andrewmawson said:
Staining is sometimes microbial activity - particularly below vices when coolant is used

True...never occurred to be until just now to perhaps try some bleach on such stains... anyone else here tried that ? I suppose bleach on iron could cause it's own problems if not careful with the application and cleanup.

DocsMachine · Oct 23, 2014

Do NOT use bleach on clean iron. It'll rust and keep rusting unless you keep it soaked to dripping in oil.

As for the stain, yes, generally speaking it's rust- oxidation, anyway. And since the rust "grows" out of the base metal, any time it rusts and you remove it, you're removing metal.

The CLR option is actually useful, I've also seen people use "Lime Away". It, like Naval Jelly, removes the rust (the oxided metal) chemically, without requiring you to remove the whole surface down to the bottom of the pits. It won't be "mirror bright", and depending on the depth of the pitting, you may always still have a "shadow" of the stain, but it beats sanding a hollow in the middle of your table.

The CLR and LA though, need to be well-rinsed away. They're acids too, that can, in the right circumstances, cause rust themselves.

Doc.

Winterfalke · Oct 23, 2014

Going to second Doc here, bleach is an oxidizing agent. That is the last thing you want to put on a steel surface. And I have had very good luck sanding things flat and smooth with WD-40, but not so much shiny. I find that polishing tends to go faster when the dust is starting to load up and giving a mild burnishing effect, but good luck keeping it flat.

rmsfla · Oct 23, 2014

My Bride help me clean one of the lathes I bought from the Government Surplus. The ways were stained very bad.
She removed the rust with Mr.Clean, The green kind and maroon Scotch-Brite .
I was totally surprised!!
Clean and bright.
You need something clean...have you bride to do it.!!
Robbie

How to make stained mill table or lathe ways look like new... 4000 grit ?

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