Stained cast iron

I have an iron-bodied Burnerd chuck that has probably sat in its unopened box, in its original greased paper for decades. There's no rust, but the brownish goo has left patches of discolouration on the chuck body. I've had similar staining on Myford accessories - again from the anti-rust grease or Ensis oil, or whatever was used.

Can I appeal to the collective wisdom of the forum participants for ideas as to how to remove this staining? No doubt gentle abrasion would do the trick, but I don't want to alter the existing, pristine surface finish. It would be good to know which chemical treatment works, non-destructively, before experimenting...

Take a look at the rebuilt Myford ML7 thread. I asked how Phil had managed to bring the slides back to a gleaming bright finish. The answer was citric acid and a brass wire brush. I haven't tried it myself yet.

Phil H

I generally use the green scouring pads, and have used Brasso, which is a soft abrasive. As with woodwork, go with the 'grain' - in this case in line with the machining or grinding texture, otherwise it looks less accurate. But in fact, the discolouration has no measurable thickness (in an ordinary workshop), and as someone said recently, use will polish the discolouration away.

Remember that the surface will rust very readily, with the removal of any surface oil or oxidation, so a drop of oil or similar rubbed all over will help. I have used Lubowax, used by woodworkers to protect their cat iron tables, but it does leave a slight waxy surface.

Bill

For starters, I would always go non abrasive, and would try cellulose thinners first.

Me too, I'd try a battery charger and washing soda. Any kind of acid would be a last resort.

It won't hold the work any better or run truer without the stains 😂

It's a matter of taste , not practicality, but I prefer machinery that looks its age. But I'm lazy

Neil

I bought a 200mm 4 Jaw chuck at an auction recently, well about a year ago. Anyway it was an Asian model clearly not used much and it was surface rusty in various places. Most importantly for me it had 4 bolt holes that would work with my Vertex index table. there was also a lot of oily turned to varnish turned to rusty brown gunk.

So what to do about cleaning it up? My normal process is uses the following tools:

Hot (strong) detergent water

Paint thinner, metholated spirit, or terpentine to deal with varnish and the like

Ajax powder as used for scouring pots, but used with a sponge not a scouring pad. The sponge greatly reduces the surface scratching caused by the Ajax. used lightly on steel you get a nice very fine grained polish. Together with old toothbrushes, also the toothbrush shape and sized wire brushes you can get at the hardware these days. to get into deeper rust.

Thumb size small pieces of well worn down fine grit wet and dry paper used with water never dry, lightly, to deal with deeper rust areas.

Oh and a new tool in the arsenal a Vileda scouring pad these are great. I hope they are available in other countries In our kitchen they last for months way better than scotch brite. but this story is not about pots! just get one and try it! I have no connection with them **LINK**

My method is based on one premise, always start with the mildest methods first so its wash with detergent water to remove grease then use the heavier methods sparingly.

I don't like acid baths for light rust as they act on the entire surface of the part.

The chuck had a few areas of light pitting where the rust was deeper, I used a wire wheel on those but not the road sweeper grade you get at the hardware, a really fine almost soft to the touch 8" x 1" wire wheel, I found a new industrial grade one at a market. I should have bought two. it does not leave deep scratches.

The said chuck came up really well, a few areas of light pitting the rest was like new.

Oh... And hot soapy water Ajax and a sponge or with the hands will make freshly machined parts look a lot brighter, it removes the grey smear left by the cutting tool.

Naturally after immersing in water the parts will need to be properly dried and oiled or Mr Rust will be back.

Regards
John

Edited By John McNamara on 25/07/2017 15:36:12

My chucks are rust stained from being stores in high humidity. I has not impaired their function in the slightest. Think of it this way: it is patina, not rust.