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What Cutting Oil To Use For Milling Mild Steel?

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Ken from ontario

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#1
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.
 

T Bredehoft

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#2
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.
 

Bob Korves

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#3
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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Bob Korves

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#4
Lubricating oils are not good choices for a cutting fluid.
 

Ken from ontario

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#6
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.
 

Wreck™Wreck

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#7
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.
 

Ken from ontario

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#8
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.
 

Video_man

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#9
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.
 

Martin W

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#10
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
 

12bolts

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#11
Check the label. Some tapping compounds are not recommended for power machining operations.

Cheers Phil
 

4gsr

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#12
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Ken from ontario

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#13
Check the label. Some tapping compounds are not recommended for power machining operations.

Cheers Phil
You are right ,the same applies to thread cutting oil also. the price difference is huge though, as video man says(post #9) , using tapping oil could be considered an overkill but for hobby use.in my case though a small can lasts a few months.
 

Ken from ontario

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#14
A big plus on Mobilmet 766 !!!

https://www.amazon.com/dp/B001VY3DJ...TF8&colid=2N1PWR8VSYL3O&coliid=I389PT37QWARAC

Not a bad deal from Amazon and free shipping!

I also use a product called Tapfree for drill and tapping, but I see that Amazon is not carrying this anymore.

https://www.amazon.com/Tapfree-Exce...e=UTF8&qid=1483916818&sr=1-2&keywords=tapfree
How do you like Tap Free Excel? I can get the 16 oz bottle in Canada for $17 and change.
http://iws.onlinesupply.ca/accessory-or-part/lubricants-spray-liquid/TF30316
 

Wreck™Wreck

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#15
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.
Don't do it, you will only make a mess, it does help however. I keep a spray bottle of coolant near a largish lathe that I often run, when one part is required and I am to lazy to set up the guards to keep the coolant from hitting the ceiling and co-workers, they find this impolite for some reason. A collet chuck eliminates much of the coolant flinging created by a scroll chucks jaws.

Set up a 1200 part job on a CNC chucker last week, 3/8" part in a 8" 3-Jaw with full flood coolant at 1500 RPM's, the operator came to me after an hour and told me that the machine was smoking. It wasn't but the big ugly chuck jaws turn the coolant into mist at that speed.
 

4gsr

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#17
How do you like Tap Free Excel? I can get the 16 oz bottle in Canada for $17 and change.
http://iws.onlinesupply.ca/accessory-or-part/lubricants-spray-liquid/TF30316
I like the stuff for drill and tapping holes only. As wreck said, it gets messy using it for any other operations. I like the Mobilmet 766, fill an spill Mate with it and use an acid brush to apply. Use it mainly on the mill. On the lathe, use it for cutting threads primarily. I'll apply the 766 on the surfaces on the finish cuts on the lathe at times.
 
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Dan_S

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#18
I'm still working my way through a gallon of Mobil Mobilmet Omicron that I bought years ago. It's designed to be both a lubricating and cutting oil, sadly you can't buy it anymore. Supposedly Mobilmet 426 is it's replacement.
 

eastokie

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#19
i use ATF (auto trans fluid) its 90 % mineral oil, works good in steel, i have a large supply of used from trans overhauls, ..pour it through a couple of shop towles,filter out most comtaninates..
 

Ken from ontario

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#20
i use ATF (auto trans fluid) its 90 % mineral oil, works good in steel, i have a large supply of used from trans overhauls, ..pour it through a couple of shop towels,filter out most contaminants..
Never thought ATF could be used for machining, someone mentioned I could use Remington gun oil! I still have a small bottle Hoppe's 9, maybe I'll give that a try.
 

Bob Korves

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#21
The relevant part starts at 3:00 and goes to 10:55
 

Ken from ontario

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#22
Thank for the video Bob,I have seen a couple of his other videos ,the man is very knowledgeable,he get his point across very clearly.
 

Bob Korves

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Thank for the video Bob,I have seen a couple of his other videos ,the man is very knowledgeable,he get his point across very clearly.
Yes, Ken. I am the sort of person that does not just want to know what I should do, I want to know why, and in a way that makes sense so I can remember it. Knowledge is power. Regurgitation just smells bad...
 
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