What Cutting Oil To Use For Milling Mild Steel?

Ken from ontario

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I'd like to know what lubricant do you use for machining mild steel(tapping oil? Synthetic 10W motor oil?, cooling fluid?), I have been using the leftover tapping oil from the shop I used to work at many years ago but it's running out , I went to order some more and wow, there's all kind of cutting oils on the market,I chose Tap Magic so far, but it's $16 for 4 ounces, is there a better choice? how about Safe Tap?

Another question, I was wondering if any of you ever spray cooling fluid to save your cutting tools?I'm trying to avoid cooling fluid on my mini mill , spraying water/oil mixture is messy IMHO,plus, I need to put some type of tray under the mill which is not practical the way I'm set up.
 
Tap Magic is as good as it gets, I get my 4 oz bottles for $4.50 or so, local purchase from a distributor.

In all honesty, 5 to 10 wt motor oil would be almost as good, probably at 75%, as are most other oils.

WD40 is not a lubricant, it's a water displacement fluid. It works, but so does lighter fluid.

Look around for Tap Magic. I've still got a 16 oz can left over from before the took the good stuff out. I only use it for tapping nasty stuff.
 
Mobilmet 766. It is good for all ferrous metals that I have worked on. I usually use Anchor Lube on stainless and anywhere that its thick paste consistency is useful. Neither of those two smell bad. On aluminum I use kerosene or WD40, whichever is convenient. Kerosene is a lot cheaper and works just as well.

You said milling, and that is what my paragraph above relates to. For threading and tapping I use either Mobilmet, dark sulfur containing stinky oil, or some old Rapid Tap I have around that is chlorinated, in order from easy to tough steels. Kerosene or WD40 is fine for most aluminum.
 
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Lubricating oils are not good choices for a cutting fluid.
 
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Lubricating oils are not good choices for a cutting fluid.
+1.
Where I worked (many years ago) we used to fabricate parts using 11 Gauge stainless steel, only cutting/tapping oil was allowed as the lubricant for punches.
 
Tap Magic is as good as it gets, I get my 4 oz bottles for $4.50 or so, local purchase from a distributor.

In all honesty, 5 to 10 wt motor oil would be almost as good, probably at 75%, as are most other oils.

WD40 is not a lubricant, it's a water displacement fluid. It works, but so does lighter fluid.

Look around for Tap Magic. I've still got a 16 oz can left over from before the took the good stuff out. I only use it for tapping nasty stuff.
Thanks ,I'm going to order the 4 ounce can for now, what's available is the new stuff only , have read a few praises on the older formula also but overall, all reviews are good,the tapping oil I'm using right now has such an awful odor, I still smell it on my hands 2 days after.
 
Do your machines have the ability to use water soluble coolant? If so use it for most work aside from tapping.

Screw machines often use a light cutting oil in a flood system though I would recommend this with an open machine.

Try some different liquids and find out what works for your application, some work extremely well but will leave a mess, lard oil comes to mind yet nothing beats it for copper work.
 
Do your machines have the ability to use water soluble coolant? If so use it for most work aside from tapping.
.
I'm using a mini mill , it's not setup for coolant at all.
The only way a mixed coolant might work (hypothetically) is to put some in a spray bottle and spray it on the piece.
 
I use thread cutting oil from the orange big box store, less than $10 for a large bottle. Small amount applied with a flux brush does the job. I have also used a water-soluble semi-synthetic (Astro-Cut made by Monroe) in a spray bottle to cool the material when milling stainless, as it heats up when face milling. IMHO the expensive tapping fluids are for just that, tapping. Overkill for general mild steel milling and turning, I think.
 
Hi Ken
KBC has many different cutting oils fairly cheap. They have an all purpose synthetic cutting oil for $28.99 a gallon as well as many others. Check there web site. I have bought from them in the past with no problems.
I have been using up a gallon of dark cutting oil that I got with my mill when I purchased it. Smokes way too much though.
Cheers
Martin
 
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