Coolant/Lubricant for Cutting Aluminium

(Jim C.) #1

First, is coolant/lubricant needed at all for aluminium? I use ZrN coated endmills for aluminium and 6061 Al.

If so, what kind of coolant or lubricant should I use? I am currently using WD-40. Spraying some to the cutting area reduces noise significantly and also washes some chips to the side. It gets loud soon and chips start to pile up if I don’t apply WD-40 for a while, so I need to basically sit in front of the machine with the can in my hand when cutting aluminium. Other than that it seems to work well for me, but I have never tried anything else.

I wonder if using a dam made of hot glue or a similar pool will work for aluminium? I am worried about chips getting trapped in the pool and especially slots and cause chip recut.

I’d also to choose something safe that is not hazardous to my health, and easy to clean.


(Mark Bellon) #2

Dry machining of Al and Al alloy (e.g. 6061) is fine. One must be realistic about their feeds and speeds.

Certainly coated end mills help but do consider a high quality single flute end mill (e.g. Onsrud). There are a lot of advantages to using a single flute. Here is a good explanation:

Cutting fluids provide three services - lubrication, cooling and swarf removal. That improves the finish and reduces friction - one can cut a faster.

Cutting fluids are often designed to be mixed with water but they themselves are often chemically nasty (and have health concerns). For instance, they need to be disposed of properly (much like used car oil). Machine shops have a source that takes the used oil and recycles or disposes it properly.

A health issue with cutting fluids is when they aerosolized - drops tiny enough to become airborne - they can breathed in.

Cutting fluids work best when they applied continuously. Many will have seen the videos of the high end mills practically flooding the stock with cutting fluid. The volume flow helps to perform the third function - swarf removal. Once a the stock is machined, ideally one doesn’t want to machine the pieces of stock which have been removed from the stock again (and again). The heavy flow washes the swarf away.

In small CNC machines one usually cannot do this - or cannot do this easily - as it makes quite a mess. The solutions also make it hard to work in wood and with spoiler board - spoiler boards (usually MDF) are sponges for cutting fluid - they start to decay rapidly. Woods will often absorb the fluids also.

By-the-by, one of the reasons end mills are “up cut” (seemingly by default) is that the “up cut” removes the swarf from the cutting area and ejects it “up”. It’s far from a perfect process but it’s MUCH better than what happens with a “down cut” tool.

The high volume of cutting fluid is a significant expense and experiments have been performed for decades looking to reduce these costs. One of the solutions is very applicable to small CNC machines - micro dripping. Here, the application of cutting fluid is adjusted to be “just enough” - the drip rate is tiny, is applied right to the cutting area, and amount is often so small that virtually nothing accumulates.

This is an example of one of the finest units I know of. It’s on my personal buy list:

The necessary destruction or recycling of cutting fluids is a major expense. This is where advances is cutting fluids come into play - environmentally friendly cutting fluids. Typically, these are soy based and work as well or better than traditional formulations. Here is an example:

There are many others.

I’ve seen plenty of WD-40 as a cutting fluid approaches before. It’s not really a lubricant. The vendor even says so. It’s a penetrating oil designed to break up rust and remove water and soil. While it does help with cutting - almost any fluid with oil in it will - it’s not not a lubricant and so I would recommend buying a real cutting fluid.

Choose an environmentally friendly - hence must less dangerous to health - one.



There are certainly materials that require using cutting fluids that cannot be the environmentally friendly ones. This is especially true with High Speed Machining (HSM) and super speed spindle (up to 60K RPM). We’re not going to be attempting these things so, in general, go for the healthiest ones.


There is nothing stopping one from micro-dropping cutting fluid themselves… a real pain, but it can be done.

(Jim C.) #3

Thanks for the information! The dispenser looks great. Let us know if you have tried it!

By the way, WD-40 doesn’t have fish oil according to the company!

(Kevin Carrico) #4

in our shop we purchase WD40 by the gallon – specifically for cutting and threading aluminum… it works wonderfully.

(Danny Harper) #5

Brush the stock with Paraffin,thats all you really need…

I use a 2 flute,45 helix cutter with the SO3 @ 200mm/min .12 DoP @ 10000RPM and it comes out very smooth.

This was dry cut.

You can see in the bottom contour the significance of chip clearing,because of its size it was hard to get the chips out which resulted in much ‘smooshing’ of chips into the face. I have modified my S03 with a very simple and cheap airsystem now which pretty much stops that.

(Mark Bellon) #6

Thanks for sharing this!

Elsewhere on the forum, I’ve mentioned swarf removal as an important feature in finish quality.

If you’re really into air clearance, consider a vortex tube! One can get swarf clearance AND cooling - lubrication!


(Danny Harper) #7

I went in for a £20 aquarium air pump, bit of hose and a nozzle off an old air gun…XD
The air pump is very quiet and is continuous duty.
It clears a 1" circle around the cutter but doesnt have so much puff as to turn the cut area into a chip storm.

I also order my cuts left to right so you dont run over the dust piles.
Have a pic!

Which reminds me…I should finish mounting it perhaps? Hahahahaaa.

All in,that mod cost me £25 and has had the most significant effect to cut quality.

(Mark Bellon) #8

Nicely done! Can’t beat the price! The aquarium pump is a great idea!

I’ve seen other designs use the compressors for the tiny, hand held, paint sprayers… but those are more expensive than aquarium pumps.

Is the spindle under M code control?

There have been studies done - multiple times - that show that an air jet on the cutting is “not bad” as a lubricant. To reach “pretty close to the liquid lubricant”, a vortex tube was necessary.

An air stream that is really cold is surprisingly effective as a lubricant. The downside, if there is one, is that a significant pressure is required to generate the cold air stream - one needs a good compressor (which has moving parts and makes noise).

Vortex tubes can be amazingly small and are often mounted on the CNC machine (so the cool air has a short distance to travel) or the bed.

The air stream as a lubricant approach is perfectly suitable for metals and plastics.

It’s a very bad idea when milling friable (“easily crumbed”) materials (e.g. wood, FR4, Garolite, carbon composite, Fiberglass) since this lofts the tiny particles which are very hazardous to ones health. With friable materials, one goes in the opposite direction - vacuum - and uses a dust head to contain the mess and ensure pick up.

A dust head is also appropriate for (some) plastics as well. Many plastics, while not friable, do generate swarf that is small enough to be lofted by a dust head… which minimizes (or removes) the after job clean up.


(David Johnson) #9

Thanks @B_NEGATIVE great solution on the aquarium pump.
I modded it for the Nomad below.
you can grab the stl and find instructions over here:
Instructions, Parts and Models for this mod.

(Danny Harper) #10

Im glad you like it,how is it working for you?

(David Johnson) #11

works great, nomad doesnt create large chips so the modest air-flow is just right to keep the path clear of debris.

(Kevin Carrico) #12

who cares how it works — it looks AMAZING!!! :slight_smile:

(Danny Harper) #13

Good stuff,I plan on reducing the nozzle size some more,Im thinking the back pressure will quieten the pump some more and have a better effect at the cut face. Been busy recently in Taiwan so I haven’t been ‘working’…I plan on using copper brake line to form more around the mount and get closer to the tool with a better angle.

(Pascal) #14

Since two weeks i use a similar solution to cool down my part and gently remove the swarf.
My system works with a AquaForte Hi-Flow V60 and produce at minimum resistance 800 ml/sec.

While changing my controller board it was easy to get the air tube trough the cable funnel.
You can see it action here:
btw don’t wonder my there are sticky swarfs around. I used a little amount of cutting oil before to reduce the impact while plunging (doesn’t working that well).

(mikep) #15

I’ve been using a couple loc-line’s on a T. You can get them right down there next to the cutting area, and still move them out of the way to put tools in the collet. It’s pretty cheap. The most expensive part was probably the needle valve ( ) between the compressor and a bit of silicone tubing that runs to the T, the T is strapped to the front of the carriage for now. With the valve, can run very low pressure (more of a “puff” than a “stream”), which is enough to clear the area immediately at the cut without blowing things around too much. I’d MUCH rather be running vacuum for this, but…well…I’m using what I’ve got, and a decent vac setup just isn’t in the cards for now.

(Francisco Montes) #16

I purchased the above pump and have received it already. Now, I’m just waiting for my Nomad to arrive so that I can start milling. Thank you for the info and details. I’ll be looking on how to adapt a vac of some sort and tie into my dust collection system. I run two 60w laser engravers along with a wood lathe that I have dust collection setup for and its great.

(Peter Lundh) #17

Hi all- Here is my implementation of air cooling for the Nomad 883 ‘Classic’. I’ve set the Arduino Uno to 2sec ON and 18sec OFF (below). It works very well using 0.01DOC; 8feed; 1speed (inch) with 3flute 1.5mm flat end bit on 6061 1/2inch aluminium. Have made a heatsink overnight (at my own risk).


  1. Relay

  2. Arduino

    digitalWrite(outPin, HIGH);
    digitalWrite(outPin, LOW);

  3. any 5v USB power supply

  4. Fused 12v power supply, or equivalent

  5. 12v air pump, or equivalent

  6. Postit 100±10µm to measure Z zero

  7. Nomad Air Mod

  8. Airline tube and 3D printed clamps. Tube is glued to clamps using 2-component epoxi glue.

  9. Nozzle (see post above)