Another Dumb Cutting Oil Question

[jimemack]

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

 

[Daver]

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.

 

[Ray C]

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

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

 

[PurpLev]

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

 

[Tom Griffin]

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

 

[onecut jimmy]

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?

 

[DMS]

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.

 

[onecut jimmy]

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.

I'll say this again, "There are no such things as dumb questions. You wouldn't know anything unless some one taught you. or it's in your dNA.

The question can be answered by looking at some of the pictures on here. look at the South bend Lathes and mills. There is nothing under them or anywhere to catch the coolan or oil or whatr have you. If you used on them it would be all over the floor. Obviously they didn't use flood coolant, that's the term for having a hose contiously running coolant on the cutter.
So it follows you must be able to cut without coolant or with something that won' run all over the place.

I absolutely would not recommend mist coolant sprays. The vapor in the air made some of my employees very sick. You can use lubricating oils on the part Any oil will do but there are some with special properties designed for just that purpose.
I used flood coolant in all my machines and black sulfinated oil on those that had to be brush applied.

I uploaded a picture from Crucible steel fabricating book fo stainless steel.
It is their recommendation for Tapping . Note what they say about using oil and grease.

 

[DMS]

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).

 

[jimemack]

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