# WD40 & cast-iron



## The_Apprentice (Jul 7, 2017)

Well I don't know.

I've read in many places that one should spray WD40 over their new mini-lathe (and adding oil), including on the cast-iron bits....


And then elsewhere on other sites I will read that putting WD40 on any cast-iron is a definite no-no... as though it will cause some harm to the metal.

I am a bit confused on this, and curious what the majority has to say here. 

Thanks in advance.


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## Jonathans (Jul 7, 2017)

I have often used WD40 on my tools, including cast iron, old and new, and have never seen
any negative reactions to the metal. This is the first and only time I have ever heard this. 
Where do you hear that from?


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## Eremius (Jul 7, 2017)

The_Apprentice said:


> Well I don't know.
> 
> I've read in many places that one should spray WD40 over their new mini-lathe (and adding oil), including on the cast-iron bits....
> 
> ...


I don't think the problem is that you shouldn't use WD-40 at all but that you shouldn't use it expecting it to protect.  WD-40 is not a protectant and will allow your equipment to rust.


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## Bob Korves (Jul 7, 2017)

WD40 will not hurt cast iron, but will not do much to help it, either.  WD40 is mostly kerosene or a very similar aromatic hydrocarbon.  WD stands for "water displacing."  That is what WD40 was designed for, not for lubrication, not for corrosion protection.  WD40 frees up stuck mechanisms short term, but gums them up long term.


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## 4GSR (Jul 7, 2017)

If you're in a high humidity area, don't use WD-40 on any bare metal surfaces including cast iron.  Unless you want the brownish patina that it will leave over a short period of time.


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## Silverbullet (Jul 7, 2017)

You should see what it does to a beautifully blued Belgian Browning shotgun barrel , left in a safe sprayed down with wd40 . When it came to me to clean up I was about sick , treat a high grade gun with the cheapest crap ever. I got it back to like new but it and he was lucky. One reason ill never have in my gun box.


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## pdentrem (Jul 7, 2017)

I use spray can of Rust Check or Krown, which ever is near the hand at the time. Spread with an oily cloth. They will not evaporate away leaving a brown varnish like residue that WD40 does.
Pierre


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## chips&more (Jul 7, 2017)

I learned my lesson many years ago the hard way. Sprayed a nice shiny piece of metal with WD40 thinking it would help keep the rust away. Maybe it does for the first few weeks/months. But after that it attracted the rust. It looked like I left it out in the weather for years to rust. Never again, I only use WD40 now to remove black pen marks.


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## hman (Jul 7, 2017)

There are lots of good alternatives ... Boeshield T-9, Fluid Film (if you don't mind the sheep-like smell), and Frog Lube.


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## Doubleeboy (Jul 7, 2017)

IMO leaving a tool out in the weather is about the same as treating it with WD40.  WD40 has to be the most overblown hype ever in the tool, handyman dept.  If you want something not to rust keep it clean, dry and avoid large temperature and humidity swings.  Hi humidity is not a problem if tool is clean and air is kept moving.  I know now some one is going to tell us how WD40 gives them the best woodies, mixes great drinks, and makes everything work perfect......  same guys use bar oil for way oil.


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## royesses (Jul 7, 2017)

I use fluid film on my mini. Seems to work ok as I have no rust on mine. I've been told the old timer machinists used to use pure lanolin but I have not verified that. Fluid film is lanolin in a carrier that evaporates. Lanolin is made by scraping sheep's skin. That's most likely why it smells. Doesn't bother me.

Roy


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## Chipper5783 (Jul 7, 2017)

I think of WD40 as spray on solvent - which is quite useful.  I often use brake clean (or equivalent aerosol cleaners), but sometimes it is just too dry.  Grab a can of WD40, it cleans stuff well enough and wipes clean.

WD40 is a great product for what it is good at (whoa, that is deep), just don't expect it to do a good job of protecting metal surfaces.


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## The_Apprentice (Jul 8, 2017)

Alright, thanks guys.

So, WD40 basically has its lathe use ONLY for cleaning up THINGS... Not to be used for anything else, or PROTECTION of any kind. 

Got it.


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## Bob Korves (Jul 8, 2017)

I think of WD40 as basically kerosene in a spray can.  Saves having to pour the kerosene into a squirt bottle.  I can buy the kerosene by the gallon for pennies on the dollar compared to WD40, and I am not too lazy to fill and label a squirt bottle...


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## mikey (Jul 8, 2017)

The_Apprentice said:


> Alright, thanks guys.
> 
> So, WD40 basically has its lathe use ONLY for cleaning up THINGS... Not to be used for anything else, or PROTECTION of any kind.
> 
> Got it.



Well, it does make a pretty good cutting lube for aluminum.


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## The_Apprentice (Jul 8, 2017)

mikey said:


> Well, it does make a pretty good cutting lube for aluminum.



Ahh yes, I have read that a few times recently. So I guess I'll keep one handy near by after all.


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## mikey (Jul 8, 2017)

WD-40 is basically mineral spirits (or similar stuff) + a little oil + a surfactant to break up oil. Lots of anecdotal stuff from guys who make their own magic mix (usually mineral spirits + a little oil) for turning aluminum. This has been going on for years. WD-40 works well for turning/cutting aluminum but there are better cutting fluids for that. 

101 uses for this stuff but I agree with the guys that you should not use it for coating/preserving machined surfaces or on anything with a precision orifice. Over time, it forms a brown varnish that is difficult to remove (acetone gets it off).


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## yendor (Jul 8, 2017)

I think the Original poster and the comment to spray WD-40 all over their NEW Lathe may have been to use it as a solvent to clean off all the cosmoline and heavy crap used to protect it during initial shipping and storage.

WD-40 is great for that, but once cleaned up he needs to switch to something better.


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## The_Apprentice (Jul 8, 2017)

In relation to WD-40 & Aluminum as a COOLANT, I did read today that because of the very low melting point of aluminum, the swarf and material has a tendency to melt and WELD itself to the cutting tool. Has that been a common problem with mini-lathes?

I already read further information that as for cutting/cooling-oil, vegetable oil is the preferred for home hobbyists as a coolant, as it can be diluted in water, while mineral oil can not. The problem, is the smell over time. Well, who knew?

And then I read something about cutting cast-iron. Apparently it is also a big NO-NO to use any form of oil or coolant on cast-iron when cutting it... but cutting dry is ok as cast-iron has its own form of graphite which aids in turning.

So... productive reading day.


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## mikey (Jul 8, 2017)

Aluminum tends to adhere to a cutting tool edge; this is called a Built Up Edge, or BUE. It is unclear if the aluminum welds to the cutter but however it forms it adheres very tightly, thereby ruining any cutting action. This applies to lathe tools and milling cutters. Coolants and cutting fluids prevent and/or reduce the formation of a BUE. WD-40 does this very well when cutting aluminum. It also alters the chip form, although this is most readily seen with carbide tooling. 

You will find that a BUE will most readily form on carbide tools. It is less of an issue with a properly ground HSS tool ground for aluminum.

As far as I know, oil - any oil - is immiscible in water so no, it doesn't work as a coolant but some forms of oil can be used as a cutting oil or aid. Crisco comes to mind.

As for cast iron, yes, it is cut dry. Oil will form an extremely abrasive slurry that will wear your tool and your lathe very quickly. A dry cut allows the chips to clear from the cut, thereby reducing wear.

There are many cutting oils/coolants and you will learn to use different ones for different materials. WD-40 works well for aluminum but the aluminum-specific fluids are better; Relton A-9 for one. Specific operations may also influence your choices. For example, a sulfur-based cutting oil produces better results when threading or knurling, which produce extreme pressures at the tool interface.

Just as important as coolants or cutting oils is your choice of tooling. Mini-lathes in general are not rigid or fast enough to use carbide tooling to full advantage. HSS tools will, in general, work better on these smaller lathes. A properly ground tool will allow a little lathe to cut like a much bigger one so look into tool grinding. One popular option (I have not used them) for many hobby guys are the tangential tool holders that allow a novice to quickly grind and use HSS tools at low cost. I think if I was a new hobby guy with a mini-lathe, I would use one of these tangential tools until I could learn to grind a conventional HSS lathe tool. You can also used honed brazed carbide tooling but they will cut with higher cutting forces. I would avoid carbide insert tooling if I were you; your lathe is just not rigid enough or fast enough to use it.

Lots to learn and think about but give it time and it will come.


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## amsoilman (Jul 8, 2017)

Use my Amsoil heavy duty metal protector for long-term storage.  Amsoil regular metal protector does not gum up firearms.  We recently introduced firearm cleaner and protector


Sent from my iPad using Tapatalk


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## pineyfolks (Jul 8, 2017)




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## strantor (Jul 9, 2017)

When I read more than once people said WD40 is kerosene, I wanted to reply with what I "knew" about WD40 ingredients. I've "known" for years that the main ingredient of WD40 is fish oil. I swear I read that somewhere very official, it was the truth. But I felt I would be challenged on that so I needed to cite my source. Went to the WD40 website and they deny any fish oil is in it. They say it's a secret recipe nobody knows what is in it but definately not fish oil. Now I have to know what it is. The answer was only a google away. These guys analyzed it with a gas chromatograph; reverse engineered the "secret" recipe. No kerosene in it either.

http://www.wired.com/2009/04/st-whatsinside-6


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## hman (Jul 9, 2017)

WD40 MSDS:
Bulk liquid - https://wd40.com/files/pdf/msds-wd482671453.pdf
Aerosol - https://www.cla.purdue.edu/polsci/documents/safetydocs/msdadocs/wd40.pdf

Wiki article on kerosene - https://en.wikipedia.org/wiki/Kerosene

Per the MSDS, WD40 contains 45-50% "aliphatic hydrocarbons."  The Wiki article states that kerosene is largely "alkanes" (and naphthenes, which are ring-shaped alkanes).  For all you non-chemists, the terms "aliphatic hydrocarbon" and "alkane" are synonymous.


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