# Another Dumb Cutting Oil Question



## jimemack (Apr 26, 2013)

I am wondering of the requirement for cutting oil for mini machines, as it applies to CNC use. I'm not sure, due to the non-stop nature of the CNC process, that it's an absolute requirement or if I can get away with no cutting oil, and under what circumstances.

If this questions is really, really dumb, you may signify by not responding whatsoever and accept my sincerest of apologies.

Jim


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## Daver (Apr 26, 2013)

My completely inexperienced and uneducated take on that would be...
It all depends!  What material are you cutting, how deep are your cuts, what feed rate..etc.

The bottom line, if you generate too much heat, your tools are getting dull real fast, or you can't get the surface finish you expected... try some cussing oil and see if it improves.


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## Ray C (Apr 26, 2013)

I have no experience with CNC machines (but I do have an underlying interest in them).  That said...It's easy with a manual machine to stop and apply cutting oil as needed.  On a CNC machine, things are moving under-power outside of the immediate control of the operator.  As such, my hands won't go near the cutting-zone of that machine.  -Period!

Also, are you talking about high speed CNC?  With 10,000+ RPM spindle speeds etc, you must have cooling -moreso than cutting lubrication.

I've been using mist coolant/lubricant on my manual machines recently -and I like it a whole lot!  The only time I'm using cutting oil  now is for slow speed operations like threading and knurling (although I have not had any knurling come my way lately).


Ray




jimemack said:


> I am wondering of the requirement for cutting oil for mini machines, as it applies to CNC use. I'm not sure, due to the non-stop nature of the CNC process, that it's an absolute requirement or if I can get away with no cutting oil, and under what circumstances.
> 
> If this questions is really, really dumb, you may signify by not responding whatsoever and accept my sincerest of apologies.
> 
> Jim


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## PurpLev (Apr 26, 2013)

that depends on your operation - if you are generating a lot of heat (heavier cuts, harder materials) then you definitely want to have some form of cooling operation be it flood coolant, mist, or spray


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## Tom Griffin (Apr 26, 2013)

Cutting oil is commonly used for manual threading or for manual parting on the lathe. The metal removal rate on a CNC machine is much higher than you'll ever see with a hobby type milling machine, which is why they require coolant. CNC machines, or any high output industrial machine use a water based cutting fluid to cool the tools. It's definitely optional on your mini mill and for anything other than production, it's usually more trouble than it's worth.

Tom


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## onecut jimmy (Apr 26, 2013)

There really is no such thing as a dumb question. Questions are used to acquire knowledge. How can that be dumb.
I won't blow my own horn (People who try to do that usually Fart.
I will say I have had ample and extensive experience with the aplications of both coolant and cutting oils.

IMO You use coolant when you want to reduce the temperature. You use oil when you want to reduce friction.

There are compounds that do both and compounds that specialise in reducing friction. 

If you are familiar with the simple machines you know that all cutting tools are wedges and they function by wedging molecules of the material you are cutting apart. That action is usually accelerated and suported by reducing friction 

As the speed of either the part or tool increases that same action because friction generates heat will get hot and require coolant. 

SO The right combintion of both is best. 
By coincedence I got a call this morning from a hobbyist friend who was tapping stainless steel and having a problem . I told him to try a black sulfinated oil I had givenm. He called me back about an hour ago and said it worked great. The problem was solved For instance , What would you call Tap Magic?


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## DMS (Apr 26, 2013)

It depends, on a lot really. There are a couple places where you want a cutting fluid (not limiting this to cutting oil), and some places where you absolutely do not. And there are also some places where you want it, but need to be carefeull how you apply it. Due to the nature of CNC, having some automated method of applying coolant is best, unless you want to follow the tool around applying fluid with a paintbrush periodically; I find this tedious, and maybe just a little (moderately dangerous). I did it till I had a better way. Some of the common cases I know of.

Places where you want coolant

1) Aluminum: It is sticky, nasty stuff that will form a wad on the end of your nice new endmill if you're not careful. If you aren't paying attention, your machine will crack that baby in two, or rip your part out of the vice, maybe both. The solution is a small amount of cutting fluid to avoid the dreaded built up edge. WD-40 works well, but the smell gets to me. I have been using Coolmist77 in a shop built fogbuster clone. I LOVE IT!!!!
2) Low conductivity materials like stainless steel and titanium. These materials will generate heat at the cutting zone, and it will leave slowly, which causes warping if you don't get rid of it somehow.
3) Plastics: cause they melt and swell when they get hot, and that is no fun

Places where you need to be careful about using coolant

1) Hardened materials. Cut them dry. It's very exciting, not sure many people need to do this.
2) Carbide tooling. If you use coolant with carbide, you have to either use it constantly and evenly, or not at all. Spraying an already hot carbide cutter with cutting fluid will cause a rapid change in temperature that will cause it to fail early (the cutting edges crack). If you're using HSS cutters, you don't have to worry about this. 

There was a good article in Digital Machinist last year on the reasons to use coolant. It was written by the guy that runs CNCCookbook, so he might have some related stuff on his site. Basically his point was that there are 3 reasons to use "coolant". Chip clearing, lubrication, and cooling. Cooling was last on his list. Its a good article (might have been a series) if you can find them.


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## onecut jimmy (Apr 30, 2013)

jimemack said:


> I am wondering of the requirement for cutting oil for mini machines, as it applies to CNC use. I'm not sure, due to the non-stop nature of the CNC process, that it's an absolute requirement or if I can get away with no cutting oil, and under what circumstances.
> 
> If this questions is really, really dumb, you may signify by not responding whatsoever and accept my sincerest of apologies.
> 
> ...


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## DMS (Apr 30, 2013)

I agree with the statement about misters. I had a Noga mister, and ran into problems when using it (mostly sore throat the next day). I have been using a shop-built "Fogbuster" clone, and have not run into the same issues (no "mist" hanging in the air). There was another thread discussing this recently. Some folks claimed they got their misters adjusted so that they didn't have a mist problem (I think low air pressure, and raising the coolant tank were the variables to adjust).


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## jimemack (Apr 30, 2013)

Oh, there ARE dumb questions. Here is a sampling:

Why can't I see my reflection in the mirror on TV?
Is it illegal to name a dog after a movie?
Is there any possible way of making 2+2=5?
Is it possible to feel like a sandwich?
How do you spell government?


Anyway, thank you all for the valuable input. I think I'll rig something up to the relay and test it. All  need is a pump to start experimenting. I'm just trying to stop buying things I'll never use.

Thanks again,
Jim


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## onecut jimmy (Apr 30, 2013)

jimemack said:


> Oh, there ARE dumb questions. Here is a sampling:
> 
> Why can't I see my reflection in the mirror on TV?
> Is it illegal to name a dog after a movie?
> ...


   Jim: I don't know the answers to any of those questions.

But before you spend any money get your self a liquid soap dispenser. You know the ones like Ajax you squeeze them and the soap shoots out. pit some coolant  in it and try it. See if it makes a difference. I personally(I actually did) would just start with plain motor oil . It may surprise you. I mean plain no detergent or synthetic. If you decide you want to go for a coolant pump. I have 2 for  sale with tanks.
Good Luck Jimmy D


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## DMS (Apr 30, 2013)

*Re: Another Cutting Oil Question*

2+2= 5 for sufficiently large values of 2...


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## Mid Day Machining (May 1, 2013)

*Re: Another Cutting Oil Question*



jimemack said:


> I am wondering of the requirement for cutting oil for mini machines, as it applies to CNC use. I'm not sure, due to the non-stop nature of the CNC process, that it's an absolute requirement or if I can get away with no cutting oil, and under what circumstances.
> 
> 
> 
> Jim



Whether or not you need cutting oil depends entirely on what you are cutting and with what kind of tool.

If you're cutting 6061 aluminum dry, you had better be ready to have your cutter clogged with chips because they will stick to it. You can run 7075 dry for milling, but you need lubrication for drilling, reaming and tapping.

Some stainless steels actually work better dry for ruffing. It just depends on what kind of cutter you are using. If you run it dry, with the right feed and speed, the chips come off a nice amber color and the chips actually carry the head away.


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## jimemack (May 1, 2013)

*Re: Another Cutting Oil Question*

It seems someone renamed my thread. I am against all forms of censorship. I am an American. What country is this forum based?


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## Rbeckett (May 1, 2013)

*Re: Another Cutting Oil Question*

Dont know who changed it but I will endeavour to find out who did it and why. What was the original header and the original spelling? Since it got changed I have no way of determining what it was before. If you will PM me I will look into this and we can discuss who and why it happened. That's the best I can do for you right now, just give me a chance to see what happened first.
Bob


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