Rust converter vs rust remover for lathe ways?

Just a Sparky · May 30, 2020

Maybe someone's answered this before but the forum search didn't really help me out.

Is it safe to use a rust converter for light surface rust on lathe ways? The sort that passivates the rust into some sort of black oxide via the use of phosphoric acid? Or do I need to stick to the (more difficult to apply) rust removers that slowly dissolve the oxides away?

I just don't want to destroy the accuracy of my ways if it turns out there is an appreciable difference between the two.

Thanks for any insight on this.

howieranger · May 30, 2020

Rust always seems to be proud of the parent surface so leaving it sticking up would not be a good idea. Remove the rust in a way that causes the least wear to the parent surface. I am sure there are many threads on rust removal to search.

swatkins · May 30, 2020

Rust changes the level of the ways. Converting the rust to something else just messes with the thickness even more...

WD40 and a razor blade is a easy way to remove light rust.

72bwhite · May 30, 2020

not if you ever want to use it
that stuff is harder then wood pecker lips
bad enough when you use converter on car body parts.

eKretz · May 31, 2020

For removing rust from precise surfaces I like to use a steel scraper to remove the bulk of any rust, followed by a relatively fine *flattened* honing stone used with mineral spirits as a lubricant.

dian · May 31, 2020

what is a rust converter? what is a remover? phosphoric or evaporust? if you do it right you can brush/clean the metal easily. then there are "converters" often based on epoxy that produce a hard coating (think gas tank restorer).

DDoug · May 31, 2020

eKretz said:
For removing rust from precise surfaces I like to use a steel scraper to remove the bulk of any rust, followed by a relatively fine *flattened* honing stone used with mineral spirits as a lubricant.

Yes, but you've still got pockets of very hard iron oxide abrasive sitting in the pits.
Ready to dislodge as the parts slide over each other.

Try the electrolysis method.

henrya · May 31, 2020

Brass brushes and a polarized oil like PG2000 works really well.

donie · May 31, 2020

Brass brush with PB Blaster,or Acetone and ATF mix took care of this small problem.

The brass brush reacts with the mix, but it is still work,

This photo I find interesting, the rust removed from the very front of the ways on the knee is unworn because the saddle doesn't travel that far, but it shows the original scraping. Rust does damage machine ways, how much may depend on the quality of the cast iron.

eKretz · May 31, 2020

digger doug said:
Yes, but you've still got pockets of very hard iron oxide abrasive sitting in the pits.
Ready to dislodge as the parts slide over each other.

Try the electrolysis method.

I've used it, it works well but it isn't very useful on things like a lathe bed... Unless you've got a lot bigger containers sitting around than I do. A wire brush can get down into pits if necessary.

sealark37 · May 31, 2020

I have tried rust converter in several applications and environments. It should never be used on any surface that depends upon dimensional stability. A better name for rust converter would be rust delayer. It simply forms a scab that is soon pushed up by further oxidation.

dian · May 31, 2020

well, on my od grider i soaked paper towels in 20% phosphoric acid, put severel layers on the ways, covered them with thin plastic and let soak for a few hours. then clean and repeat. worked well.

Rex TX · May 31, 2020

Don't use a convertor, as others have said. Use Evaporust or something similar - a chelant. Use nothing with acid. Evaporust will not harm the metal, nor the paint. It only removes rust and grease and hardened coolant.

How big is the bed? Last one I did I built a pine trough of 2x12 lumber, lined it with pond liner from HD. I used 5 gallons of Evaporust, raising the level with all the other rusty parts until the bed was fully covered. Worked great.

You can also use Evaporust by using a pond pump to recirculate it. If you have a lathe made for pump coolant, you have the hard part done. Just cover the rusty parts with cloth, rig up a distribution system to keep them wet.

5 gallons or ER is about $75 last I bought. There are cheaper chelant formulas on the market now, but I haven't tried them.

Lastly, if it's mostly surface rust, a razor scraper and light oil, followed by 0000 steel wool and even lighter oil (WD40, mineral spirits) works just fine.

I use WD40 in a trigger spray, along with brush and steel wool for initial cleanup and evaluation. It's amazing how much better a machine can look with a few hours of this attention.

EPAIII · May 31, 2020

A rust remover will remove the rust, even the rust that is down in a pit or scratch. If used according to the instructions, it will not remove any of the non-rusted metal. That means that you should not leave the rust remover on for days. Apply it, give it the directed time to work, and then clean it off. And then oil the ways to prevent new rust from forming.

My lathe's ways are somewhat worn and probably need to be reground and/or scraped. I would not hesitate to even carefully use a fine or medium grade of Scotch Brite pads on them if rust formed. I would use them carefully. I would use them evenly on the entire surface of all the ways to even out any wear. That would include the area of the ways that is normally under the headstock. And, of course, a complete cleanup after. Would I recommend this for your lathe? I do not know. Only you can answer that question. Try the rust remover first, please. It will probably do the job. \

The best way to prevent rust on any machine is regular use. And regular oiling. And controlling the humidity in the shop.

donie · May 31, 2020

I must be the only one that has actually done it, you cant talk the rust off!
Seriously, the ones that do it use the Acetone/ATF mix, brass brush and hard work.

Phil in Montana · May 31, 2020

Ya, the old I don't want to do it the hard way, Use elbow grease and scrap. sand and polish the rust away.....only way its going to happen....Phil

ptsmith · May 31, 2020

I might be wrong, but I interpreted this discussion to be about avoiding harming the ways, not about avoiding work.

Just a Sparky · May 31, 2020

Answering a few of the questions, it's an old 1946 13" South Bend toolroom with a 6 foot bed. Minimal wear on the soft ways - some of the original scraping can still be made out here and there on the right half of the saddle ways. Hasn't moved in around 40 years, but it was clearly well maintained sans a couple of 'oopsies' here and there. The thick layers of oil and grease covering it kept it mostly preserved aside from some light to medium-light fuzz. Nothing bad enough to cause appreciable pitting except for some onesie-twosie stuff.

Interesting to hear that EvapoRust helps with cutting grease since the entire machine is caked in tar-like congealed oil. The stuff is like wax. I thought at first the spindle was seized when I inspected the machine - but when I pulled the bearing caps I realized that's just how thick all the oil has gotten over 40 years. I put some fresh stuff into there and came back a week later to find it spinning like a dream.

Thinking I might soak the bare parts in carb cleaner and hit the rest of it with an evaporating chlorine- or petroleum-based degreaser like Lectra Clean... then see what some EvapoRust does to the fuzzy spots.

mattthemuppet · May 31, 2020

donie said:
Brass brush with PB Blaster,or Acetone and ATF mix took care of this small problem.

The brass brush reacts with the mix, but it is still work,

WHAT?! I just need to add some PB Blaster to a rusty crumbly paint machine and it turns into something beautiful like that? Holy shit!

Yeah yeah, I'm sorry, couldn't help myself. First person I've seen on here from Walla Walla too - lived there for 3 years a while back. I miss the Blue Mountains and the wheat fields.

To the OP - careful using Evaporust without submerging the part. Although you can soak paper towels in Evaporust, lay them on the bed and then wrap it all with clingfilm (saran wrap?) to prevent them drying out, you can get some crazy ass patterns from the paper towels. I tried it on a rusty ratty drill press column (and no, it didn't end up looking like Donie's machine) and it left a lot of patterns on the metal that weren't easy to remove, though it did remove the rust. I ended up giving the column a rub down with some oil and telling the buyer that it was "camo pattern".

Just a Sparky · May 31, 2020

Heh, 'camo pattern'. Nice. Well, maybe I'll keep searching for the right rust remover that does the job for me but at least it seems like I've got the general answer that I need: That rust converters are not really what I'm looking for to clean precision surfaces.

Anyone had experience with CRC's rust remover? I've had good experiences with their products on the job so I figure their offering might be worth consideration. They even list engine components and machine parts as some of their intended applications. :scratchchin:

Rust converter vs rust remover for lathe ways?

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