Asking advice: WD40 for coolant on CNC mill?

[Paul_the_engineer]

Hello everyone. New to this forum, new to CNC. I recently sold off my Bridgeport series 1 Jhead, bought a Tormach 1100 CNC. Then I was horrified of the machine so I took a solidworks course, and Ansys course and a CNC course. I'm getting through it. Still freaked out by something called a mill that doesn't have cranks and dials.....

OK then, so the machine has a large sump, a pump, Gcode easily turns on coolant, I built a reasonable enclosure out of acrylic. But I have some concerns. I hear that water based coolant tends to rust things. Water, ions, corrosion, anodes, cathodes....yup, that's consistent. I'd rather not hear of some magic snake oil in water that doesn't have these problems. they all do. Further, I don't like the notion that these things can develop bacterial problems. So do I drill a hole in the tank, install a water heater element bung, screw in an element and kill off the microscopic beasties once a week? whew, who wants that? Water based coolant is off the table in my humble shop for these reasons, snake oil or not.

But then I was thinking of simply using WD40. I've used it for eons, welded over the stuff, got it way too hot, made careful note of the left over slime once the kerosene vapes off. How bad do you reckon the fire hazard is? I don't like having lots of kerosene surface area exposed in the tank....so maybe add a plenum and a baffle, or a P-trap.......

Please, asking your thoughts. Sure, the specific heat of WD40 isn't anywhere near water, it won't get rid of the heat as efficiently....but it's better than air no? It won't rust stuff, no electrolyte action with disimilar metals (cast from the Kurt vise vs the cast from the table), no galvanic potential. Just a simple, cheap dielectric lubricant that always seemed pretty hard to burn.

PS, I have no interest in working at ludicrous speeds. Easy enough to slow down and wait a while. She's still faster than old 9" x 42" "Hank", although I do miss the knee.

Thanks for the read, may the mill rise up to meet you! (I put mine on risers, tired of bending over machines designed for short people).

 

[Mtndew]

Water based coolant is off the table in my humble shop for these reasons,

Thousands of machine shops use it daily and for decades. If it's rusting then the water/coolant ratio is not correct.
If you want a smoke filled shop with zero cooling properties, then by all means use WD-40.

Get a 5 gallon pail of some decent coolant, a refractometer, a fish tank oxygenator from your local pet store to prevent bacteria from building up, and never look back.

 

[Ox]

For your app, I would prolly just go with cutting oil.

Way higher flash point than WD I am sure.
Way better lube.
Won't evap.
Won't stink.

But it will smoke, depending on how hard you are pushing things and how little flood volume you have.
Not as much as the WD would tho either.

I cannot imagine going with WD!
WD is good for squirt bottle apps for alum.
Leave it at that....

Catch an open pan of WD on fire, say good bye to the buidling....


-------------------

Think Snow Eh!
Ox

 

[Garwood]

Hello

Username checks out.

 

[Ox]

[snicker]

You know - you're getting awfully cynical these days....

Did you recently have a mile-marker birthday?


---------------

Think Snow Eh!
Ox

 

[memphisjed]

“PS, I have no interest in working at ludicrous speeds. Easy enough to slow down and wait a while. She's still faster than old 9" x 42" "Hank", although I do miss the knee”

It is good you do not want to work at ludicrous speeds, coolant is not your limiting factor. Coolant will help your machine cut better, go faster, look stylish while doing it, and cost less in cutters. Coolant is cheap, carbide is expensive.
You can mix your coolant rich. One of the times more is more- within reason.

 

[Orange Vise]

I hear that water based coolant tends to rust things. Water, ions, corrosion, anodes, cathodes....yup, that's consistent.

Keep the concentration high (10-12%) and the issues are mitigated, albeit not eliminated.

WD40 is not the way to go. At best it's a makeshift MQL solution for aluminum, but it fogs much worse than real MQL lubricants.

 

[1032screw]

I think you need to do a bit more research into what you after in terms of performance for your application before making a decision.

I would highly recommend not using WD-40. First as state above it is not a machine tool coolant. It would be expensive to fill a 12 gallon sump ($360+). It is a huge fire hazard. It would smell a lot as the volatile solvents in it evaporate off. It may strip paint off a machine if left on surfaces. Most of all in my experience it isn't all that great as a rust preventative.

In regards to machine tool coolants I think correct nomenclature is the starting point in your research. "Water based coolant" isn't a real thing. There are straight oil coolants, emulsified oil coolants and miscible synthetic and semi-synthetic coolant. The last three dilute with water but are not water based.

In my opinion the biggest obstacle in regards to coolant in a hobby machine is lack of regular use. Regular use and maintenance of coolant keeps coolant healthy. As stated by Mtndew an aquarium pump in a sump can go a long way to preventing bad bacteria build up. Regular maintenance and use is the other critical part. In my experience rusting is only a problem if you get the concentration wrong at the start and make the coolant to water ratio too lean. In my experience if a coolant starts at the correct concentration, over time the water evaporates out during use or while sitting in an open sump, causing a higher coolant concentration and increasing rust prevention.

Really if you don't want to mess with flood coolant and the maintenance involved you should look into mist or MQL coolant systems. They also have their pro's and cons when compared against flood coolants. In my experience mist coolants that are diluted with water is where real rust problems can come from.

 

[Vancbiker]

Username checks out.

Best comment!

The OP’s question and stance on coolant is so stupid that it sounds to me like we’re being trolled.

 

[Mtndew]

it sounds to me like we’re being trolled.

I wouldn't go that far.
There are a TON of people that have no idea what it takes to machine parts correctly. They learn from a book, from YouTube, advice from a friend, etc... when in reality what they should do is get a job in an actual machine shop for a couple of years before jumping head first into it with zero experience.

We can make this profession look really easy, but it took a LOT of time and experience for us to get to where we are. That's what most newbies don't grasp.

 

[memphisjed]

Mr dew, I think op is doing it for fun, not professionally. Having toys and being a hack is part of hobbies. Sometimes the same get really good and do some extraordinary things because of lack of deadlines, herd and tribe mentality.
The wd40... not one of those extraordinary things.

 

[Ox]

For your app, I would prolly just go with cutting oil.

Way higher flash point than WD I am sure.
Way better lube.
Won't evap.
Won't stink.

But it will smoke, depending on how hard you are pushing things and how little flood volume you have.
Not as much as the WD would tho either.

I cannot imagine going with WD!
WD is good for squirt bottle apps for alum.
Leave it at that....

Catch an open pan of WD on fire, say good bye to the buidling....


-------------------

Think Snow Eh!
Ox

Actually, for your app, if it was me, I'd prolly just run down to Quality Farm and Fleet and fetch a bucket of hydraulic fluid and call it good enough.

You're not gunna want the smell of sulfur in your garage.
Or the hassel of actually trying to find a bucket of cutting oil for that matter.

I have heard of some folks using reg hydro oil, and Lord knows that I have enough of it mixed into my oils. You may not git quite the tool life that you would with sulfurized cutting oil, but you're not gunna doo enough to ever tell the difference, so ...

The flash point will be a bit lower than heavy cutting oil, but it's not like it's volatile.


-------------------

Think Snow Eh!
Ox

 

[dandrummerman21]

Lol, I would like to add another angle for the engineer here.

A gallon of coolant, when mixed at 5%, might be 2 or 3$ per gallon. Even round it up to 5$ if you anticipate lots of maintenance costs and coolant changes. As water evaporates out of it, you can add thin mixes to your sump to top off.

A gallon of WD40 is 20$. And I feel like lots of it will evaporate off. What could you add to it to thin it out? Mineral spirits? Kerosene?

 

[SteveEx30]

If you use Pam cooking spray it will smell like buttered popcorn while you work

 

[Ox]

.. think you got trouble with mice in the garage now?
Wait 'till after THAT fiasco!




---------------

Think Snow Eh!
Ox

 

[JSL_MFG]

A synthetic water-soluble coolant is the best solution at the end of the day, but there are other options.

You could use a mist system which is pretty easy to install manually. Something like this: https://koolmist.com/
The mist from these guys is not fun to breathe in, so I'd rather use flood coolant like everybody else is saying.

Another option, and probably your best option, is a cold air gun, such as these: https://www.vortexair.biz/product-category/cooling/cold-air-guns/
You can slap one of these onto your machine, and you'll get pretty decent results. The downside is that they build up with ice if they're running long enough, and then that melts & rusts your table if not cleaned up quickly enough.

Really, a synthetic coolant will protect your machine from rust, prevent bacteria from ever growing in your sump, lubricate your cutter, evacuate chips, and prevent cutting-edge buildup. Best of luck!

 

[Dan from Oakland]

Put some WD40 in a cup and let it sit for a few days. It will turn into a gooey mess after the solvent evaporates.
Its good for tapping a few holes in aluminum, but not a coolant tank full.

 

[Cyclotronguy]

WD-40 makes a convenient solvent for various purposes like getting road tar off of car rims but after the stoddard solvent that makes up the bulk of it evaporates, all you have left is an awful varnish like deposit. If you feel the need for cutting oil in lieu of water based coolants, Mobil-met is excellent!

When using oil in any machine, the trick is to have a heavy flood to avoid combustion. But having said that you don't know mess, till you deal with flood oil.... EVERYWHERE!

 

[rons]

Have used Kool Mist with water. Very good at stopping rust. Only a few parts per gallon of water.
Have used WD-40 to start a fireplace burn. It burns very slowly compared to something like gasoline.

 

[13engines]

Paul-Paul-Paul... that was an award winning post you shared there. The engineer in you really stood out.

I share with you a photo of pretty much everything you'll need to have successfully coolantized machining on your new Tormach. Don't worry about rust with this stuff. Nearly impossible, and it won't kill you either. Vises mounted for weeks if not months will come off with everything underneath still good as gold. Or steel rather.



Small Shop Shopping List: You'll need some version of everything you see here. Leaving out any one item quickly downgrades your chances for coolant success.

1) QualChem 251C Coolant
2) RO/DI Unit (Pump optional)
3) Refractometer
4) Fluid Measuring Vessel/Spatula
5) Powered Mixer
6) 5-10 Gallon Mobile Bucket
7) Aerator
8) Shop vac nozzle cut like a chess castle for sucking up tramp oil off the top of the coolant. (Works better then a few "systems" I've tried.)
9) Worn out shop broom. This can't be bought. Produced from years of sweeping up chips.

Keep your concentration where it belongs and no problems will haunt you. Don't make the mistake of making your initial batch with RO/DI. Use tap water to start. Good luck.